MCU?
12-22-2007, 12:38 AM
#11
Guest
Posts: n/a
Re: MCU?
"DougW" <I.only.read.usenet@invalid.address> wrote in message
news:VF0bj.35723$Qf1.31515@newsfe07.phx...
> bllsht wrote:
>> On Fri, 21 Dec 2007 19:13:15 -0600, "DougW"
>> <I.only.read.usenet@invalid.address> wrote:
>>
>>> JEEPR wrote:
>>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>>> excessive crank on hot start. Dealer service says metering pins are
>>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>>> metered the MCU and it is faulty. New part is $800.
>>>> Are they on the right track or are they trying to pull one?
>>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>>> with out replacement?
>>>
>>> New? It probably just needs rebuilt.
>>> Dealers charge way too much. $800 is a pure ripoff.
>>>
>>> For example, the rebuild kit for a 72-90 Weber Carb (which I think
>>> is the one in your jeep) Please make sure before you buy any
>>> rebuild kit.
>>>
>>> A full rebuilt carb from Napa is only $324
>>>
>>> An OEM carb from chryslerpartsdirect.com is $251.10
>>> The Factory overhaul kit is #30.38
>>>
>>> Any decent mechanic can do the work for you and probably for $100 +
>>> parts.
>>
>> MCU = Microprocessor Control Unit. He's talking computer, not carb.
>
> doh.
>
> I got stuck on pins and fuel/air.
>
> Isn't that the carb they do the nutter bypass on?
That's the one. Mike would know if the Nutter bypass is cool to do in
Ontario. I would think so. Google "Nutter bypass".
Cheers,
Earle
--
Posted via a free Usenet account from http://www.teranews.com
news:VF0bj.35723$Qf1.31515@newsfe07.phx...
> bllsht wrote:
>> On Fri, 21 Dec 2007 19:13:15 -0600, "DougW"
>> <I.only.read.usenet@invalid.address> wrote:
>>
>>> JEEPR wrote:
>>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>>> excessive crank on hot start. Dealer service says metering pins are
>>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>>> metered the MCU and it is faulty. New part is $800.
>>>> Are they on the right track or are they trying to pull one?
>>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>>> with out replacement?
>>>
>>> New? It probably just needs rebuilt.
>>> Dealers charge way too much. $800 is a pure ripoff.
>>>
>>> For example, the rebuild kit for a 72-90 Weber Carb (which I think
>>> is the one in your jeep) Please make sure before you buy any
>>> rebuild kit.
>>>
>>> A full rebuilt carb from Napa is only $324
>>>
>>> An OEM carb from chryslerpartsdirect.com is $251.10
>>> The Factory overhaul kit is #30.38
>>>
>>> Any decent mechanic can do the work for you and probably for $100 +
>>> parts.
>>
>> MCU = Microprocessor Control Unit. He's talking computer, not carb.
>
> doh.
>
> I got stuck on pins and fuel/air.
>
> Isn't that the carb they do the nutter bypass on?
That's the one. Mike would know if the Nutter bypass is cool to do in
Ontario. I would think so. Google "Nutter bypass".
Cheers,
Earle
--
Posted via a free Usenet account from http://www.teranews.com
12-22-2007, 10:56 AM
#12
Guest
Posts: n/a
Re: MCU?
The MCU could be toast. A used one at the wreckers is cheap. I would
also try the 'Jeep' shops for a used one. 'DON'T' give any of them
money up front though, none of them are reliable enough for that. I
know too many horror stories first hand even.
The O2 sensor could also just be bad so the MCU has nothing to base
changing the mix on....
Any number of sensors could have failed causing the MCU to go into 'limp
home' mode.
The trouble is, they don't have a computer to tell them anything about
it so have to shoot blind unless they really know 4.2's and their
systems. There is a test block on the firewall for the sensors that
needs a special 'Jeep' computer to read or knowledge with a multimeter.
Only one more E test too eh. Too bad it messed up just then.
The hard cold and hot starts could be as simple as having the gas filter
in upside down. The filter has two outlets, you need to make sure the
center outlet goes to the carb and the 'top' outlet goes to the return
line. if the return line isn't up top, the gas siphons back to the tank
when it sits and blows back to the tank on a hot shutdown effectively
vapor locking it.
Where abouts in Ontario are you? If you are close to Toronto, I know
how to double check the pins and the O2 and other sensors to see if
there is anything happening there. I also can make them pass emissions,
but I kill the computer doing it so it has to be manually tuned up.
This is called the 'Nutter' bypass.
You also might want to just run it through the sniffer to see how far
off passing emissions it now is.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
JEEPR wrote:
> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
> crank on hot start. Dealer service says metering pins are not moving in and
> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
> faulty. New part is $800.
> Are they on the right track or are they trying to pull one?
> Trying to get ready for the ontario E-Test. Will it pass the e-test with
> out replacement?
>
>
also try the 'Jeep' shops for a used one. 'DON'T' give any of them
money up front though, none of them are reliable enough for that. I
know too many horror stories first hand even.
The O2 sensor could also just be bad so the MCU has nothing to base
changing the mix on....
Any number of sensors could have failed causing the MCU to go into 'limp
home' mode.
The trouble is, they don't have a computer to tell them anything about
it so have to shoot blind unless they really know 4.2's and their
systems. There is a test block on the firewall for the sensors that
needs a special 'Jeep' computer to read or knowledge with a multimeter.
Only one more E test too eh. Too bad it messed up just then.
The hard cold and hot starts could be as simple as having the gas filter
in upside down. The filter has two outlets, you need to make sure the
center outlet goes to the carb and the 'top' outlet goes to the return
line. if the return line isn't up top, the gas siphons back to the tank
when it sits and blows back to the tank on a hot shutdown effectively
vapor locking it.
Where abouts in Ontario are you? If you are close to Toronto, I know
how to double check the pins and the O2 and other sensors to see if
there is anything happening there. I also can make them pass emissions,
but I kill the computer doing it so it has to be manually tuned up.
This is called the 'Nutter' bypass.
You also might want to just run it through the sniffer to see how far
off passing emissions it now is.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
JEEPR wrote:
> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
> crank on hot start. Dealer service says metering pins are not moving in and
> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
> faulty. New part is $800.
> Are they on the right track or are they trying to pull one?
> Trying to get ready for the ontario E-Test. Will it pass the e-test with
> out replacement?
>
>
12-22-2007, 10:56 AM
#13
Guest
Posts: n/a
Re: MCU?
The MCU could be toast. A used one at the wreckers is cheap. I would
also try the 'Jeep' shops for a used one. 'DON'T' give any of them
money up front though, none of them are reliable enough for that. I
know too many horror stories first hand even.
The O2 sensor could also just be bad so the MCU has nothing to base
changing the mix on....
Any number of sensors could have failed causing the MCU to go into 'limp
home' mode.
The trouble is, they don't have a computer to tell them anything about
it so have to shoot blind unless they really know 4.2's and their
systems. There is a test block on the firewall for the sensors that
needs a special 'Jeep' computer to read or knowledge with a multimeter.
Only one more E test too eh. Too bad it messed up just then.
The hard cold and hot starts could be as simple as having the gas filter
in upside down. The filter has two outlets, you need to make sure the
center outlet goes to the carb and the 'top' outlet goes to the return
line. if the return line isn't up top, the gas siphons back to the tank
when it sits and blows back to the tank on a hot shutdown effectively
vapor locking it.
Where abouts in Ontario are you? If you are close to Toronto, I know
how to double check the pins and the O2 and other sensors to see if
there is anything happening there. I also can make them pass emissions,
but I kill the computer doing it so it has to be manually tuned up.
This is called the 'Nutter' bypass.
You also might want to just run it through the sniffer to see how far
off passing emissions it now is.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
JEEPR wrote:
> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
> crank on hot start. Dealer service says metering pins are not moving in and
> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
> faulty. New part is $800.
> Are they on the right track or are they trying to pull one?
> Trying to get ready for the ontario E-Test. Will it pass the e-test with
> out replacement?
>
>
also try the 'Jeep' shops for a used one. 'DON'T' give any of them
money up front though, none of them are reliable enough for that. I
know too many horror stories first hand even.
The O2 sensor could also just be bad so the MCU has nothing to base
changing the mix on....
Any number of sensors could have failed causing the MCU to go into 'limp
home' mode.
The trouble is, they don't have a computer to tell them anything about
it so have to shoot blind unless they really know 4.2's and their
systems. There is a test block on the firewall for the sensors that
needs a special 'Jeep' computer to read or knowledge with a multimeter.
Only one more E test too eh. Too bad it messed up just then.
The hard cold and hot starts could be as simple as having the gas filter
in upside down. The filter has two outlets, you need to make sure the
center outlet goes to the carb and the 'top' outlet goes to the return
line. if the return line isn't up top, the gas siphons back to the tank
when it sits and blows back to the tank on a hot shutdown effectively
vapor locking it.
Where abouts in Ontario are you? If you are close to Toronto, I know
how to double check the pins and the O2 and other sensors to see if
there is anything happening there. I also can make them pass emissions,
but I kill the computer doing it so it has to be manually tuned up.
This is called the 'Nutter' bypass.
You also might want to just run it through the sniffer to see how far
off passing emissions it now is.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
JEEPR wrote:
> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
> crank on hot start. Dealer service says metering pins are not moving in and
> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
> faulty. New part is $800.
> Are they on the right track or are they trying to pull one?
> Trying to get ready for the ontario E-Test. Will it pass the e-test with
> out replacement?
>
>
12-22-2007, 10:59 AM
#14
Guest
Posts: n/a
Re: MCU?
DougW wrote:
> DougW wrote:
>> JEEPR wrote:
>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>> excessive crank on hot start. Dealer service says metering pins are
>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>> metered the MCU and it is faulty. New part is $800.
>>> Are they on the right track or are they trying to pull one?
>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>> with out replacement?
>> New? It probably just needs rebuilt.
>> Dealers charge way too much. $800 is a pure ripoff.
>>
>> For example, the rebuild kit for a 72-90 Weber Carb (which I think is
>> the one in your jeep) Please make sure before you buy any rebuild
>> kit.
>> A full rebuilt carb from Napa is only $324
>>
>> An OEM carb from chryslerpartsdirect.com is $251.10
>> The Factory overhaul kit is #30.38
>>
>> Any decent mechanic can do the work for you and probably for $100 +
>> parts.
>
> And actually with the current exchange rate those prices will be better.
> (I priced US$)
>
> As for passing the e-test up in Ontario.. I don't have a clue. Might get
> by with some carb cleaner.
>
Canadian Tire stores even have the carb kits for about $25.00. I'll put
one in for $100.00 plus parts.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
> DougW wrote:
>> JEEPR wrote:
>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>> excessive crank on hot start. Dealer service says metering pins are
>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>> metered the MCU and it is faulty. New part is $800.
>>> Are they on the right track or are they trying to pull one?
>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>> with out replacement?
>> New? It probably just needs rebuilt.
>> Dealers charge way too much. $800 is a pure ripoff.
>>
>> For example, the rebuild kit for a 72-90 Weber Carb (which I think is
>> the one in your jeep) Please make sure before you buy any rebuild
>> kit.
>> A full rebuilt carb from Napa is only $324
>>
>> An OEM carb from chryslerpartsdirect.com is $251.10
>> The Factory overhaul kit is #30.38
>>
>> Any decent mechanic can do the work for you and probably for $100 +
>> parts.
>
> And actually with the current exchange rate those prices will be better.
> (I priced US$)
>
> As for passing the e-test up in Ontario.. I don't have a clue. Might get
> by with some carb cleaner.
>
Canadian Tire stores even have the carb kits for about $25.00. I'll put
one in for $100.00 plus parts.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
12-22-2007, 10:59 AM
#15
Guest
Posts: n/a
Re: MCU?
DougW wrote:
> DougW wrote:
>> JEEPR wrote:
>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>> excessive crank on hot start. Dealer service says metering pins are
>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>> metered the MCU and it is faulty. New part is $800.
>>> Are they on the right track or are they trying to pull one?
>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>> with out replacement?
>> New? It probably just needs rebuilt.
>> Dealers charge way too much. $800 is a pure ripoff.
>>
>> For example, the rebuild kit for a 72-90 Weber Carb (which I think is
>> the one in your jeep) Please make sure before you buy any rebuild
>> kit.
>> A full rebuilt carb from Napa is only $324
>>
>> An OEM carb from chryslerpartsdirect.com is $251.10
>> The Factory overhaul kit is #30.38
>>
>> Any decent mechanic can do the work for you and probably for $100 +
>> parts.
>
> And actually with the current exchange rate those prices will be better.
> (I priced US$)
>
> As for passing the e-test up in Ontario.. I don't have a clue. Might get
> by with some carb cleaner.
>
Canadian Tire stores even have the carb kits for about $25.00. I'll put
one in for $100.00 plus parts.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
> DougW wrote:
>> JEEPR wrote:
>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>> excessive crank on hot start. Dealer service says metering pins are
>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>> metered the MCU and it is faulty. New part is $800.
>>> Are they on the right track or are they trying to pull one?
>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>> with out replacement?
>> New? It probably just needs rebuilt.
>> Dealers charge way too much. $800 is a pure ripoff.
>>
>> For example, the rebuild kit for a 72-90 Weber Carb (which I think is
>> the one in your jeep) Please make sure before you buy any rebuild
>> kit.
>> A full rebuilt carb from Napa is only $324
>>
>> An OEM carb from chryslerpartsdirect.com is $251.10
>> The Factory overhaul kit is #30.38
>>
>> Any decent mechanic can do the work for you and probably for $100 +
>> parts.
>
> And actually with the current exchange rate those prices will be better.
> (I priced US$)
>
> As for passing the e-test up in Ontario.. I don't have a clue. Might get
> by with some carb cleaner.
>
Canadian Tire stores even have the carb kits for about $25.00. I'll put
one in for $100.00 plus parts.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
12-22-2007, 02:58 PM
#16
Guest
Posts: n/a
Re: MCU?
On Fri, 21 Dec 2007 22:47:51 -0600, "DougW"
<I.only.read.usenet@invalid.address> wrote:
>bllsht wrote:
>> On Fri, 21 Dec 2007 19:13:15 -0600, "DougW"
>> <I.only.read.usenet@invalid.address> wrote:
>>
>>> JEEPR wrote:
>>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>>> excessive crank on hot start. Dealer service says metering pins are
>>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>>> metered the MCU and it is faulty. New part is $800.
>>>> Are they on the right track or are they trying to pull one?
>>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>>> with out replacement?
>>>
>>> New? It probably just needs rebuilt.
>>> Dealers charge way too much. $800 is a pure ripoff.
>>>
>>> For example, the rebuild kit for a 72-90 Weber Carb (which I think
>>> is the one in your jeep) Please make sure before you buy any
>>> rebuild kit.
>>>
>>> A full rebuilt carb from Napa is only $324
>>>
>>> An OEM carb from chryslerpartsdirect.com is $251.10
>>> The Factory overhaul kit is #30.38
>>>
>>> Any decent mechanic can do the work for you and probably for $100 +
>>> parts.
>>
>> MCU = Microprocessor Control Unit. He's talking computer, not carb.
>
>doh.
>
>I got stuck on pins and fuel/air.
>
>Isn't that the carb they do the nutter bypass on?
>
>Either way, the ECM is US$294
>
>And I still wonder if the metering pins are not a part of the cause
>as they can also stick.
These had the Carter BBD carb and are the ones folks do the bypass on.
I've never seen the pins stick, but have seen several problems with
the stepper motor that moves the pins. The motor can stick or fail
electrically. Most common failures are becomming stuck, or failing
"open" electrically. Replacing the stepper motor will remedy this.
Less common but more expensive is when the stepper motor shorts
internally. This will take the driver in the MCU out with it.
Easy test with an ohm meter.
<I.only.read.usenet@invalid.address> wrote:
>bllsht wrote:
>> On Fri, 21 Dec 2007 19:13:15 -0600, "DougW"
>> <I.only.read.usenet@invalid.address> wrote:
>>
>>> JEEPR wrote:
>>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>>> excessive crank on hot start. Dealer service says metering pins are
>>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>>> metered the MCU and it is faulty. New part is $800.
>>>> Are they on the right track or are they trying to pull one?
>>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>>> with out replacement?
>>>
>>> New? It probably just needs rebuilt.
>>> Dealers charge way too much. $800 is a pure ripoff.
>>>
>>> For example, the rebuild kit for a 72-90 Weber Carb (which I think
>>> is the one in your jeep) Please make sure before you buy any
>>> rebuild kit.
>>>
>>> A full rebuilt carb from Napa is only $324
>>>
>>> An OEM carb from chryslerpartsdirect.com is $251.10
>>> The Factory overhaul kit is #30.38
>>>
>>> Any decent mechanic can do the work for you and probably for $100 +
>>> parts.
>>
>> MCU = Microprocessor Control Unit. He's talking computer, not carb.
>
>doh.
>
>I got stuck on pins and fuel/air.
>
>Isn't that the carb they do the nutter bypass on?
>
>Either way, the ECM is US$294
>
>And I still wonder if the metering pins are not a part of the cause
>as they can also stick.
These had the Carter BBD carb and are the ones folks do the bypass on.
I've never seen the pins stick, but have seen several problems with
the stepper motor that moves the pins. The motor can stick or fail
electrically. Most common failures are becomming stuck, or failing
"open" electrically. Replacing the stepper motor will remedy this.
Less common but more expensive is when the stepper motor shorts
internally. This will take the driver in the MCU out with it.
Easy test with an ohm meter.
12-22-2007, 02:58 PM
#17
Guest
Posts: n/a
Re: MCU?
On Fri, 21 Dec 2007 22:47:51 -0600, "DougW"
<I.only.read.usenet@invalid.address> wrote:
>bllsht wrote:
>> On Fri, 21 Dec 2007 19:13:15 -0600, "DougW"
>> <I.only.read.usenet@invalid.address> wrote:
>>
>>> JEEPR wrote:
>>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>>> excessive crank on hot start. Dealer service says metering pins are
>>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>>> metered the MCU and it is faulty. New part is $800.
>>>> Are they on the right track or are they trying to pull one?
>>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>>> with out replacement?
>>>
>>> New? It probably just needs rebuilt.
>>> Dealers charge way too much. $800 is a pure ripoff.
>>>
>>> For example, the rebuild kit for a 72-90 Weber Carb (which I think
>>> is the one in your jeep) Please make sure before you buy any
>>> rebuild kit.
>>>
>>> A full rebuilt carb from Napa is only $324
>>>
>>> An OEM carb from chryslerpartsdirect.com is $251.10
>>> The Factory overhaul kit is #30.38
>>>
>>> Any decent mechanic can do the work for you and probably for $100 +
>>> parts.
>>
>> MCU = Microprocessor Control Unit. He's talking computer, not carb.
>
>doh.
>
>I got stuck on pins and fuel/air.
>
>Isn't that the carb they do the nutter bypass on?
>
>Either way, the ECM is US$294
>
>And I still wonder if the metering pins are not a part of the cause
>as they can also stick.
These had the Carter BBD carb and are the ones folks do the bypass on.
I've never seen the pins stick, but have seen several problems with
the stepper motor that moves the pins. The motor can stick or fail
electrically. Most common failures are becomming stuck, or failing
"open" electrically. Replacing the stepper motor will remedy this.
Less common but more expensive is when the stepper motor shorts
internally. This will take the driver in the MCU out with it.
Easy test with an ohm meter.
<I.only.read.usenet@invalid.address> wrote:
>bllsht wrote:
>> On Fri, 21 Dec 2007 19:13:15 -0600, "DougW"
>> <I.only.read.usenet@invalid.address> wrote:
>>
>>> JEEPR wrote:
>>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and
>>>> excessive crank on hot start. Dealer service says metering pins are
>>>> not moving in and out to regulate air and fuel.. Says the mechanic
>>>> metered the MCU and it is faulty. New part is $800.
>>>> Are they on the right track or are they trying to pull one?
>>>> Trying to get ready for the ontario E-Test. Will it pass the e-test
>>>> with out replacement?
>>>
>>> New? It probably just needs rebuilt.
>>> Dealers charge way too much. $800 is a pure ripoff.
>>>
>>> For example, the rebuild kit for a 72-90 Weber Carb (which I think
>>> is the one in your jeep) Please make sure before you buy any
>>> rebuild kit.
>>>
>>> A full rebuilt carb from Napa is only $324
>>>
>>> An OEM carb from chryslerpartsdirect.com is $251.10
>>> The Factory overhaul kit is #30.38
>>>
>>> Any decent mechanic can do the work for you and probably for $100 +
>>> parts.
>>
>> MCU = Microprocessor Control Unit. He's talking computer, not carb.
>
>doh.
>
>I got stuck on pins and fuel/air.
>
>Isn't that the carb they do the nutter bypass on?
>
>Either way, the ECM is US$294
>
>And I still wonder if the metering pins are not a part of the cause
>as they can also stick.
These had the Carter BBD carb and are the ones folks do the bypass on.
I've never seen the pins stick, but have seen several problems with
the stepper motor that moves the pins. The motor can stick or fail
electrically. Most common failures are becomming stuck, or failing
"open" electrically. Replacing the stepper motor will remedy this.
Less common but more expensive is when the stepper motor shorts
internally. This will take the driver in the MCU out with it.
Easy test with an ohm meter.
12-22-2007, 03:50 PM
#18
Guest
Posts: n/a
Re: MCU?
On Sat, 22 Dec 2007 10:56:38 -0500, Mike Romain <romainm@sympatico.ca>
wrote:
>The MCU could be toast. A used one at the wreckers is cheap. I would
>also try the 'Jeep' shops for a used one. 'DON'T' give any of them
>money up front though, none of them are reliable enough for that. I
>know too many horror stories first hand even.
>
>The O2 sensor could also just be bad so the MCU has nothing to base
>changing the mix on....
>
>Any number of sensors could have failed causing the MCU to go into 'limp
>home' mode.
>
Even with an input causing only open loop operation, the pins should
still move. It should also complete the initialization process when
you crank the engine. That is driving the pins full rich, then back to
the "centered" position. If it does this, you can pretty much
eliminate a stepper motor circuit problem.
>The trouble is, they don't have a computer to tell them anything about
>it so have to shoot blind unless they really know 4.2's and their
>systems. There is a test block on the firewall for the sensors that
>needs a special 'Jeep' computer to read or knowledge with a multimeter.
>
That special computer was pretty much just a fancy multimeter. It
couldn't do anything you couldn't do faster with a multimeter and a
handheld vacuum pump/gauge.
>Only one more E test too eh. Too bad it messed up just then.
>
>The hard cold and hot starts could be as simple as having the gas filter
>in upside down. The filter has two outlets, you need to make sure the
>center outlet goes to the carb and the 'top' outlet goes to the return
>line. if the return line isn't up top, the gas siphons back to the tank
>when it sits and blows back to the tank on a hot shutdown effectively
>vapor locking it.
>
>Where abouts in Ontario are you? If you are close to Toronto, I know
>how to double check the pins and the O2 and other sensors to see if
>there is anything happening there. I also can make them pass emissions,
>but I kill the computer doing it so it has to be manually tuned up.
>This is called the 'Nutter' bypass.
>
>You also might want to just run it through the sniffer to see how far
>off passing emissions it now is.
>
>Mike
>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>'New' frame in the works for '08. Some Canadian Bush Trip and Build
>Photos: http://mikeromainjeeptrips.shutterfly.com
>
>JEEPR wrote:
>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
>> crank on hot start. Dealer service says metering pins are not moving in and
>> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
>> faulty. New part is $800.
>> Are they on the right track or are they trying to pull one?
>> Trying to get ready for the ontario E-Test. Will it pass the e-test with
>> out replacement?
>>
>>
wrote:
>The MCU could be toast. A used one at the wreckers is cheap. I would
>also try the 'Jeep' shops for a used one. 'DON'T' give any of them
>money up front though, none of them are reliable enough for that. I
>know too many horror stories first hand even.
>
>The O2 sensor could also just be bad so the MCU has nothing to base
>changing the mix on....
>
>Any number of sensors could have failed causing the MCU to go into 'limp
>home' mode.
>
Even with an input causing only open loop operation, the pins should
still move. It should also complete the initialization process when
you crank the engine. That is driving the pins full rich, then back to
the "centered" position. If it does this, you can pretty much
eliminate a stepper motor circuit problem.
>The trouble is, they don't have a computer to tell them anything about
>it so have to shoot blind unless they really know 4.2's and their
>systems. There is a test block on the firewall for the sensors that
>needs a special 'Jeep' computer to read or knowledge with a multimeter.
>
That special computer was pretty much just a fancy multimeter. It
couldn't do anything you couldn't do faster with a multimeter and a
handheld vacuum pump/gauge.
>Only one more E test too eh. Too bad it messed up just then.
>
>The hard cold and hot starts could be as simple as having the gas filter
>in upside down. The filter has two outlets, you need to make sure the
>center outlet goes to the carb and the 'top' outlet goes to the return
>line. if the return line isn't up top, the gas siphons back to the tank
>when it sits and blows back to the tank on a hot shutdown effectively
>vapor locking it.
>
>Where abouts in Ontario are you? If you are close to Toronto, I know
>how to double check the pins and the O2 and other sensors to see if
>there is anything happening there. I also can make them pass emissions,
>but I kill the computer doing it so it has to be manually tuned up.
>This is called the 'Nutter' bypass.
>
>You also might want to just run it through the sniffer to see how far
>off passing emissions it now is.
>
>Mike
>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>'New' frame in the works for '08. Some Canadian Bush Trip and Build
>Photos: http://mikeromainjeeptrips.shutterfly.com
>
>JEEPR wrote:
>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
>> crank on hot start. Dealer service says metering pins are not moving in and
>> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
>> faulty. New part is $800.
>> Are they on the right track or are they trying to pull one?
>> Trying to get ready for the ontario E-Test. Will it pass the e-test with
>> out replacement?
>>
>>
12-22-2007, 03:50 PM
#19
Guest
Posts: n/a
Re: MCU?
On Sat, 22 Dec 2007 10:56:38 -0500, Mike Romain <romainm@sympatico.ca>
wrote:
>The MCU could be toast. A used one at the wreckers is cheap. I would
>also try the 'Jeep' shops for a used one. 'DON'T' give any of them
>money up front though, none of them are reliable enough for that. I
>know too many horror stories first hand even.
>
>The O2 sensor could also just be bad so the MCU has nothing to base
>changing the mix on....
>
>Any number of sensors could have failed causing the MCU to go into 'limp
>home' mode.
>
Even with an input causing only open loop operation, the pins should
still move. It should also complete the initialization process when
you crank the engine. That is driving the pins full rich, then back to
the "centered" position. If it does this, you can pretty much
eliminate a stepper motor circuit problem.
>The trouble is, they don't have a computer to tell them anything about
>it so have to shoot blind unless they really know 4.2's and their
>systems. There is a test block on the firewall for the sensors that
>needs a special 'Jeep' computer to read or knowledge with a multimeter.
>
That special computer was pretty much just a fancy multimeter. It
couldn't do anything you couldn't do faster with a multimeter and a
handheld vacuum pump/gauge.
>Only one more E test too eh. Too bad it messed up just then.
>
>The hard cold and hot starts could be as simple as having the gas filter
>in upside down. The filter has two outlets, you need to make sure the
>center outlet goes to the carb and the 'top' outlet goes to the return
>line. if the return line isn't up top, the gas siphons back to the tank
>when it sits and blows back to the tank on a hot shutdown effectively
>vapor locking it.
>
>Where abouts in Ontario are you? If you are close to Toronto, I know
>how to double check the pins and the O2 and other sensors to see if
>there is anything happening there. I also can make them pass emissions,
>but I kill the computer doing it so it has to be manually tuned up.
>This is called the 'Nutter' bypass.
>
>You also might want to just run it through the sniffer to see how far
>off passing emissions it now is.
>
>Mike
>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>'New' frame in the works for '08. Some Canadian Bush Trip and Build
>Photos: http://mikeromainjeeptrips.shutterfly.com
>
>JEEPR wrote:
>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
>> crank on hot start. Dealer service says metering pins are not moving in and
>> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
>> faulty. New part is $800.
>> Are they on the right track or are they trying to pull one?
>> Trying to get ready for the ontario E-Test. Will it pass the e-test with
>> out replacement?
>>
>>
wrote:
>The MCU could be toast. A used one at the wreckers is cheap. I would
>also try the 'Jeep' shops for a used one. 'DON'T' give any of them
>money up front though, none of them are reliable enough for that. I
>know too many horror stories first hand even.
>
>The O2 sensor could also just be bad so the MCU has nothing to base
>changing the mix on....
>
>Any number of sensors could have failed causing the MCU to go into 'limp
>home' mode.
>
Even with an input causing only open loop operation, the pins should
still move. It should also complete the initialization process when
you crank the engine. That is driving the pins full rich, then back to
the "centered" position. If it does this, you can pretty much
eliminate a stepper motor circuit problem.
>The trouble is, they don't have a computer to tell them anything about
>it so have to shoot blind unless they really know 4.2's and their
>systems. There is a test block on the firewall for the sensors that
>needs a special 'Jeep' computer to read or knowledge with a multimeter.
>
That special computer was pretty much just a fancy multimeter. It
couldn't do anything you couldn't do faster with a multimeter and a
handheld vacuum pump/gauge.
>Only one more E test too eh. Too bad it messed up just then.
>
>The hard cold and hot starts could be as simple as having the gas filter
>in upside down. The filter has two outlets, you need to make sure the
>center outlet goes to the carb and the 'top' outlet goes to the return
>line. if the return line isn't up top, the gas siphons back to the tank
>when it sits and blows back to the tank on a hot shutdown effectively
>vapor locking it.
>
>Where abouts in Ontario are you? If you are close to Toronto, I know
>how to double check the pins and the O2 and other sensors to see if
>there is anything happening there. I also can make them pass emissions,
>but I kill the computer doing it so it has to be manually tuned up.
>This is called the 'Nutter' bypass.
>
>You also might want to just run it through the sniffer to see how far
>off passing emissions it now is.
>
>Mike
>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>'New' frame in the works for '08. Some Canadian Bush Trip and Build
>Photos: http://mikeromainjeeptrips.shutterfly.com
>
>JEEPR wrote:
>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
>> crank on hot start. Dealer service says metering pins are not moving in and
>> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
>> faulty. New part is $800.
>> Are they on the right track or are they trying to pull one?
>> Trying to get ready for the ontario E-Test. Will it pass the e-test with
>> out replacement?
>>
>>
12-22-2007, 04:46 PM
#20
Guest
Posts: n/a
Re: MCU?
Thanks for the input!
Mike
bllsht wrote:
> On Sat, 22 Dec 2007 10:56:38 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
>> The MCU could be toast. A used one at the wreckers is cheap. I would
>> also try the 'Jeep' shops for a used one. 'DON'T' give any of them
>> money up front though, none of them are reliable enough for that. I
>> know too many horror stories first hand even.
>>
>> The O2 sensor could also just be bad so the MCU has nothing to base
>> changing the mix on....
>>
>> Any number of sensors could have failed causing the MCU to go into 'limp
>> home' mode.
>>
> Even with an input causing only open loop operation, the pins should
> still move. It should also complete the initialization process when
> you crank the engine. That is driving the pins full rich, then back to
> the "centered" position. If it does this, you can pretty much
> eliminate a stepper motor circuit problem.
>
>> The trouble is, they don't have a computer to tell them anything about
>> it so have to shoot blind unless they really know 4.2's and their
>> systems. There is a test block on the firewall for the sensors that
>> needs a special 'Jeep' computer to read or knowledge with a multimeter.
>>
> That special computer was pretty much just a fancy multimeter. It
> couldn't do anything you couldn't do faster with a multimeter and a
> handheld vacuum pump/gauge.
>
>> Only one more E test too eh. Too bad it messed up just then.
>>
>> The hard cold and hot starts could be as simple as having the gas filter
>> in upside down. The filter has two outlets, you need to make sure the
>> center outlet goes to the carb and the 'top' outlet goes to the return
>> line. if the return line isn't up top, the gas siphons back to the tank
>> when it sits and blows back to the tank on a hot shutdown effectively
>> vapor locking it.
>>
>> Where abouts in Ontario are you? If you are close to Toronto, I know
>> how to double check the pins and the O2 and other sensors to see if
>> there is anything happening there. I also can make them pass emissions,
>> but I kill the computer doing it so it has to be manually tuned up.
>> This is called the 'Nutter' bypass.
>>
>> You also might want to just run it through the sniffer to see how far
>> off passing emissions it now is.
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
>> Photos: http://mikeromainjeeptrips.shutterfly.com
>>
>> JEEPR wrote:
>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
>>> crank on hot start. Dealer service says metering pins are not moving in and
>>> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
>>> faulty. New part is $800.
>>> Are they on the right track or are they trying to pull one?
>>> Trying to get ready for the ontario E-Test. Will it pass the e-test with
>>> out replacement?
>>>
>>>
Mike
bllsht wrote:
> On Sat, 22 Dec 2007 10:56:38 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
>> The MCU could be toast. A used one at the wreckers is cheap. I would
>> also try the 'Jeep' shops for a used one. 'DON'T' give any of them
>> money up front though, none of them are reliable enough for that. I
>> know too many horror stories first hand even.
>>
>> The O2 sensor could also just be bad so the MCU has nothing to base
>> changing the mix on....
>>
>> Any number of sensors could have failed causing the MCU to go into 'limp
>> home' mode.
>>
> Even with an input causing only open loop operation, the pins should
> still move. It should also complete the initialization process when
> you crank the engine. That is driving the pins full rich, then back to
> the "centered" position. If it does this, you can pretty much
> eliminate a stepper motor circuit problem.
>
>> The trouble is, they don't have a computer to tell them anything about
>> it so have to shoot blind unless they really know 4.2's and their
>> systems. There is a test block on the firewall for the sensors that
>> needs a special 'Jeep' computer to read or knowledge with a multimeter.
>>
> That special computer was pretty much just a fancy multimeter. It
> couldn't do anything you couldn't do faster with a multimeter and a
> handheld vacuum pump/gauge.
>
>> Only one more E test too eh. Too bad it messed up just then.
>>
>> The hard cold and hot starts could be as simple as having the gas filter
>> in upside down. The filter has two outlets, you need to make sure the
>> center outlet goes to the carb and the 'top' outlet goes to the return
>> line. if the return line isn't up top, the gas siphons back to the tank
>> when it sits and blows back to the tank on a hot shutdown effectively
>> vapor locking it.
>>
>> Where abouts in Ontario are you? If you are close to Toronto, I know
>> how to double check the pins and the O2 and other sensors to see if
>> there is anything happening there. I also can make them pass emissions,
>> but I kill the computer doing it so it has to be manually tuned up.
>> This is called the 'Nutter' bypass.
>>
>> You also might want to just run it through the sniffer to see how far
>> off passing emissions it now is.
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
>> Photos: http://mikeromainjeeptrips.shutterfly.com
>>
>> JEEPR wrote:
>>> Have a 88 yj with 4.2, standard.. Rins roughon cold start and excessive
>>> crank on hot start. Dealer service says metering pins are not moving in and
>>> out to regulate air and fuel.. Says the mechanic metered the MCU and it is
>>> faulty. New part is $800.
>>> Are they on the right track or are they trying to pull one?
>>> Trying to get ready for the ontario E-Test. Will it pass the e-test with
>>> out replacement?
>>>
>>>
