Re: New Cam, Jeep will only run without TPS
 

Jeffrey DeWitt wrote:
> It seems at least as likely as the thing running with the TPS
> unplugged! THAT one I don't understand at all.

The TPS is not a critical doodad. If it goes missing the computer
will adjust based on the O2 sensor.

What you do loose is the WOT (Wide Open Trottle) signal.

My 93 will run without the TPS. I know this because I left
the darn thing disconnected. :] heh. oops.


--
DougW

Re: New Cam, Jeep will only run without TPS
 

Wonder how the engine runs with the WOT signal on all the time?

The OP said the sensor was replaced, but maybe the new one was bad or
wrong? Is it possible to connect the sensor wrong?

Jeff DeWitt

DougW wrote:
> Jeffrey DeWitt wrote:
>
>>It seems at least as likely as the thing running with the TPS
>> unplugged! THAT one I don't understand at all.
>
>
> The TPS is not a critical doodad. If it goes missing the computer
> will adjust based on the O2 sensor.
>
> What you do loose is the WOT (Wide Open Trottle) signal.
>
> My 93 will run without the TPS. I know this because I left
> the darn thing disconnected. :] heh. oops.
>
>

Re: New Cam, Jeep will only run without TPS
 

Wonder how the engine runs with the WOT signal on all the time?

The OP said the sensor was replaced, but maybe the new one was bad or
wrong? Is it possible to connect the sensor wrong?

Jeff DeWitt

DougW wrote:
> Jeffrey DeWitt wrote:
>
>>It seems at least as likely as the thing running with the TPS
>> unplugged! THAT one I don't understand at all.
>
>
> The TPS is not a critical doodad. If it goes missing the computer
> will adjust based on the O2 sensor.
>
> What you do loose is the WOT (Wide Open Trottle) signal.
>
> My 93 will run without the TPS. I know this because I left
> the darn thing disconnected. :] heh. oops.
>
>

Re: New Cam, Jeep will only run without TPS
 

Wonder how the engine runs with the WOT signal on all the time?

The OP said the sensor was replaced, but maybe the new one was bad or
wrong? Is it possible to connect the sensor wrong?

Jeff DeWitt

DougW wrote:
> Jeffrey DeWitt wrote:
>
>>It seems at least as likely as the thing running with the TPS
>> unplugged! THAT one I don't understand at all.
>
>
> The TPS is not a critical doodad. If it goes missing the computer
> will adjust based on the O2 sensor.
>
> What you do loose is the WOT (Wide Open Trottle) signal.
>
> My 93 will run without the TPS. I know this because I left
> the darn thing disconnected. :] heh. oops.
>
>

Re: New Cam, Jeep will only run without TPS
 

There is a big difference between not being able to compute the
optimal fuel and timing demands (no TPS signal), and having spark in
the wrong cylinder and no spark in the right cylinder.

You don't need a TPS to start the engine. You do need spark in the
right cylinder.

On Sun, 29 Oct 2006 21:41:32 GMT, Jeffrey DeWitt
<JeffDeWitt@nc.rr.com> wrote:

>It seems at least as likely as the thing running with the TPS unplugged!
> THAT one I don't understand at all.
>
>Jeff DeWitt
>
>bllsht wrote:
>> Not likely. If it ran at all in that condition, unplugging the TPS
>> wouldn't improve it.
>>
>> On Sun, 29 Oct 2006 13:30:11 GMT, Jeffrey DeWitt
>> <JeffDeWitt@nc.rr.com> wrote:
>>
>>
>>>That's a good point, could you have put the wires on the distributor cap
>>>one position off? I've done that and the engine will run, but sounds
>>>off and backfires when revved.
>>>
>>>Jeff DeWitt
>>>
>>>bllsht wrote:
>>>
>>>>First thing that came to my mind is that you may have the distributor
>>>>indexed incorrectly.
>>>>
>>>>With cyl. 1 at TDC, the trailing edge of the ign. rotor should be
>>>>about .020" PAST the #1 post in the distributor cap.
>>>>
>>>>With the TPS disconnected, the PCM may not be advancing the timing and
>>>>that may be enough for it to 'fire' the correct post.
>>>>
>>>>In other words, the rotor isn't pointing in the right direction when
>>>>the PCM fires the coil.
>>>>
>>>>
>>>>
>>>>On 28 Oct 2006 12:31:01 -0700, "jeepinacreek"
>>>><jeepinacreek@hotmail.com> wrote:
>>>>
>>>>
>>>>
>>>>>I recently put a new cam in my 1997 Jeep Wrangler 4.0L. I figured it
>>>>>was a great mod with out totaly stroking the motor. After completing
>>>>>the buildup and starting it for the first time, I thought great it
>>>>>runs. Then I ran up and it starting backfiring at around 1800+ RPM.
>>>>>This has been my battle for the last three months.
>>>>>
>>>>>A little about my Jeep;
>>>>>Doug thorley header
>>>>>bored out 62mm throttle
>>>>>MSD ignition
>>>>>New catalatic convertor, Flowmaster 50 exhaust Cold air intake 4in
>>>>>Curry Enterpise lift 33in tires, 4:10 gears, lockers
>>>>>
>>>>>What I have done to fix this so far;
>>>>>-Took it the dealer, they wouldn't touch it.
>>>>>-I currently have timing chain retarded -5 degree's due to pinging, cut
>>>>>down on backfiring.
>>>>>-I also had it advanced +5 degree's, caused a lot more backfiring.
>>>>>-I also ran the cam at TDC with no advance or timing. This is the
>>>>>original way I built it.
>>>>>-Changed TPS
>>>>>-Changed spark plugs, wires, cap, rotor, and coil. Currently run MSD
>>>>>ignition which I disconnected and the Jeep barely ran. Connected it
>>>>>back up and seems to be the only thing keeping it running. So I know
>>>>>the MSD works -changed O2 sensors -changed fuel pump and filters in
>>>>>tank, gas cap to.
>>>>>-Changed fuel injecters to 21LB injectors, stock is around 23.5LB -Put
>>>>>an air/fuel ratio gauge on it.
>>>>>
>>>>>So my latest attempt to get this thing running right truely has me
>>>>>scratching my head, I left the TPS wire connected disconnected, drove
>>>>>it and it runs fine. No backfire at 1800+ RPM, it doesn't surge,
>>>>>hesitate or ping or miss or run rich. It runs great, I can drive it on
>>>>>the freeway now.
>>>>>
>>>>>I am on my last leg with this thing. Anyone have any ideas or
>>>>>suggestions?????? Please help or i may put the stock cam back in.

Re: New Cam, Jeep will only run without TPS
 

There is a big difference between not being able to compute the
optimal fuel and timing demands (no TPS signal), and having spark in
the wrong cylinder and no spark in the right cylinder.

You don't need a TPS to start the engine. You do need spark in the
right cylinder.

On Sun, 29 Oct 2006 21:41:32 GMT, Jeffrey DeWitt
<JeffDeWitt@nc.rr.com> wrote:

>It seems at least as likely as the thing running with the TPS unplugged!
> THAT one I don't understand at all.
>
>Jeff DeWitt
>
>bllsht wrote:
>> Not likely. If it ran at all in that condition, unplugging the TPS
>> wouldn't improve it.
>>
>> On Sun, 29 Oct 2006 13:30:11 GMT, Jeffrey DeWitt
>> <JeffDeWitt@nc.rr.com> wrote:
>>
>>
>>>That's a good point, could you have put the wires on the distributor cap
>>>one position off? I've done that and the engine will run, but sounds
>>>off and backfires when revved.
>>>
>>>Jeff DeWitt
>>>
>>>bllsht wrote:
>>>
>>>>First thing that came to my mind is that you may have the distributor
>>>>indexed incorrectly.
>>>>
>>>>With cyl. 1 at TDC, the trailing edge of the ign. rotor should be
>>>>about .020" PAST the #1 post in the distributor cap.
>>>>
>>>>With the TPS disconnected, the PCM may not be advancing the timing and
>>>>that may be enough for it to 'fire' the correct post.
>>>>
>>>>In other words, the rotor isn't pointing in the right direction when
>>>>the PCM fires the coil.
>>>>
>>>>
>>>>
>>>>On 28 Oct 2006 12:31:01 -0700, "jeepinacreek"
>>>><jeepinacreek@hotmail.com> wrote:
>>>>
>>>>
>>>>
>>>>>I recently put a new cam in my 1997 Jeep Wrangler 4.0L. I figured it
>>>>>was a great mod with out totaly stroking the motor. After completing
>>>>>the buildup and starting it for the first time, I thought great it
>>>>>runs. Then I ran up and it starting backfiring at around 1800+ RPM.
>>>>>This has been my battle for the last three months.
>>>>>
>>>>>A little about my Jeep;
>>>>>Doug thorley header
>>>>>bored out 62mm throttle
>>>>>MSD ignition
>>>>>New catalatic convertor, Flowmaster 50 exhaust Cold air intake 4in
>>>>>Curry Enterpise lift 33in tires, 4:10 gears, lockers
>>>>>
>>>>>What I have done to fix this so far;
>>>>>-Took it the dealer, they wouldn't touch it.
>>>>>-I currently have timing chain retarded -5 degree's due to pinging, cut
>>>>>down on backfiring.
>>>>>-I also had it advanced +5 degree's, caused a lot more backfiring.
>>>>>-I also ran the cam at TDC with no advance or timing. This is the
>>>>>original way I built it.
>>>>>-Changed TPS
>>>>>-Changed spark plugs, wires, cap, rotor, and coil. Currently run MSD
>>>>>ignition which I disconnected and the Jeep barely ran. Connected it
>>>>>back up and seems to be the only thing keeping it running. So I know
>>>>>the MSD works -changed O2 sensors -changed fuel pump and filters in
>>>>>tank, gas cap to.
>>>>>-Changed fuel injecters to 21LB injectors, stock is around 23.5LB -Put
>>>>>an air/fuel ratio gauge on it.
>>>>>
>>>>>So my latest attempt to get this thing running right truely has me
>>>>>scratching my head, I left the TPS wire connected disconnected, drove
>>>>>it and it runs fine. No backfire at 1800+ RPM, it doesn't surge,
>>>>>hesitate or ping or miss or run rich. It runs great, I can drive it on
>>>>>the freeway now.
>>>>>
>>>>>I am on my last leg with this thing. Anyone have any ideas or
>>>>>suggestions?????? Please help or i may put the stock cam back in.

Re: New Cam, Jeep will only run without TPS
 

There is a big difference between not being able to compute the
optimal fuel and timing demands (no TPS signal), and having spark in
the wrong cylinder and no spark in the right cylinder.

You don't need a TPS to start the engine. You do need spark in the
right cylinder.

On Sun, 29 Oct 2006 21:41:32 GMT, Jeffrey DeWitt
<JeffDeWitt@nc.rr.com> wrote:

>It seems at least as likely as the thing running with the TPS unplugged!
> THAT one I don't understand at all.
>
>Jeff DeWitt
>
>bllsht wrote:
>> Not likely. If it ran at all in that condition, unplugging the TPS
>> wouldn't improve it.
>>
>> On Sun, 29 Oct 2006 13:30:11 GMT, Jeffrey DeWitt
>> <JeffDeWitt@nc.rr.com> wrote:
>>
>>
>>>That's a good point, could you have put the wires on the distributor cap
>>>one position off? I've done that and the engine will run, but sounds
>>>off and backfires when revved.
>>>
>>>Jeff DeWitt
>>>
>>>bllsht wrote:
>>>
>>>>First thing that came to my mind is that you may have the distributor
>>>>indexed incorrectly.
>>>>
>>>>With cyl. 1 at TDC, the trailing edge of the ign. rotor should be
>>>>about .020" PAST the #1 post in the distributor cap.
>>>>
>>>>With the TPS disconnected, the PCM may not be advancing the timing and
>>>>that may be enough for it to 'fire' the correct post.
>>>>
>>>>In other words, the rotor isn't pointing in the right direction when
>>>>the PCM fires the coil.
>>>>
>>>>
>>>>
>>>>On 28 Oct 2006 12:31:01 -0700, "jeepinacreek"
>>>><jeepinacreek@hotmail.com> wrote:
>>>>
>>>>
>>>>
>>>>>I recently put a new cam in my 1997 Jeep Wrangler 4.0L. I figured it
>>>>>was a great mod with out totaly stroking the motor. After completing
>>>>>the buildup and starting it for the first time, I thought great it
>>>>>runs. Then I ran up and it starting backfiring at around 1800+ RPM.
>>>>>This has been my battle for the last three months.
>>>>>
>>>>>A little about my Jeep;
>>>>>Doug thorley header
>>>>>bored out 62mm throttle
>>>>>MSD ignition
>>>>>New catalatic convertor, Flowmaster 50 exhaust Cold air intake 4in
>>>>>Curry Enterpise lift 33in tires, 4:10 gears, lockers
>>>>>
>>>>>What I have done to fix this so far;
>>>>>-Took it the dealer, they wouldn't touch it.
>>>>>-I currently have timing chain retarded -5 degree's due to pinging, cut
>>>>>down on backfiring.
>>>>>-I also had it advanced +5 degree's, caused a lot more backfiring.
>>>>>-I also ran the cam at TDC with no advance or timing. This is the
>>>>>original way I built it.
>>>>>-Changed TPS
>>>>>-Changed spark plugs, wires, cap, rotor, and coil. Currently run MSD
>>>>>ignition which I disconnected and the Jeep barely ran. Connected it
>>>>>back up and seems to be the only thing keeping it running. So I know
>>>>>the MSD works -changed O2 sensors -changed fuel pump and filters in
>>>>>tank, gas cap to.
>>>>>-Changed fuel injecters to 21LB injectors, stock is around 23.5LB -Put
>>>>>an air/fuel ratio gauge on it.
>>>>>
>>>>>So my latest attempt to get this thing running right truely has me
>>>>>scratching my head, I left the TPS wire connected disconnected, drove
>>>>>it and it runs fine. No backfire at 1800+ RPM, it doesn't surge,
>>>>>hesitate or ping or miss or run rich. It runs great, I can drive it on
>>>>>the freeway now.
>>>>>
>>>>>I am on my last leg with this thing. Anyone have any ideas or
>>>>>suggestions?????? Please help or i may put the stock cam back in.

Re: New Cam, Jeep will only run without TPS
 

Jeffrey DeWitt wrote:
> Wonder how the engine runs with the WOT signal on all the time?
>
> The OP said the sensor was replaced, but maybe the new one was bad or
> wrong? Is it possible to connect the sensor wrong?

At least on the ZJ it's possible. :) The shaft and tangs have to be
lined up. Thing is, if they arn't the throttle simply won't open.
(or at least that's how the ZJ acts) Some vehicles require the TPS
to be indexed by watching the voltage.

In all cases it's a good idea to reset the computer and reprogram the
range. Simply pull the battery off (or pull the fuses), have lunch,
put the battery back on. turn the key to on, (engine not running)
and slowly move the throttle between closed and wide open about
five or six times. Holding it at the limits for a few seconds.
Then turn the key off, start the car, and let it idle, drive it
normally, and eventually hit the highway.


Easy enough to test the TPS sensor. Just takes a volt meter.
(backprobe. i.e. don't pierce the wires, just slide a pin/paperclip
up the back of the connector)

with ignition on, engine not running.
Measure across the two outer wires. Should have 5 volts.
Measure between the ground wire and the center wire.
Throttle closed >200 milliVolts
Throttle wide open <4.8 Volts
As the throttle is moved between idle and WOT, the voltage
should smootly increase with no dropouts or jumps.

--
DougW

Re: New Cam, Jeep will only run without TPS
 

Jeffrey DeWitt wrote:
> Wonder how the engine runs with the WOT signal on all the time?
>
> The OP said the sensor was replaced, but maybe the new one was bad or
> wrong? Is it possible to connect the sensor wrong?

At least on the ZJ it's possible. :) The shaft and tangs have to be
lined up. Thing is, if they arn't the throttle simply won't open.
(or at least that's how the ZJ acts) Some vehicles require the TPS
to be indexed by watching the voltage.

In all cases it's a good idea to reset the computer and reprogram the
range. Simply pull the battery off (or pull the fuses), have lunch,
put the battery back on. turn the key to on, (engine not running)
and slowly move the throttle between closed and wide open about
five or six times. Holding it at the limits for a few seconds.
Then turn the key off, start the car, and let it idle, drive it
normally, and eventually hit the highway.


Easy enough to test the TPS sensor. Just takes a volt meter.
(backprobe. i.e. don't pierce the wires, just slide a pin/paperclip
up the back of the connector)

with ignition on, engine not running.
Measure across the two outer wires. Should have 5 volts.
Measure between the ground wire and the center wire.
Throttle closed >200 milliVolts
Throttle wide open <4.8 Volts
As the throttle is moved between idle and WOT, the voltage
should smootly increase with no dropouts or jumps.

--
DougW

Re: New Cam, Jeep will only run without TPS
 

Jeffrey DeWitt wrote:
> Wonder how the engine runs with the WOT signal on all the time?
>
> The OP said the sensor was replaced, but maybe the new one was bad or
> wrong? Is it possible to connect the sensor wrong?

At least on the ZJ it's possible. :) The shaft and tangs have to be
lined up. Thing is, if they arn't the throttle simply won't open.
(or at least that's how the ZJ acts) Some vehicles require the TPS
to be indexed by watching the voltage.

In all cases it's a good idea to reset the computer and reprogram the
range. Simply pull the battery off (or pull the fuses), have lunch,
put the battery back on. turn the key to on, (engine not running)
and slowly move the throttle between closed and wide open about
five or six times. Holding it at the limits for a few seconds.
Then turn the key off, start the car, and let it idle, drive it
normally, and eventually hit the highway.


Easy enough to test the TPS sensor. Just takes a volt meter.
(backprobe. i.e. don't pierce the wires, just slide a pin/paperclip
up the back of the connector)

with ignition on, engine not running.
Measure across the two outer wires. Should have 5 volts.
Measure between the ground wire and the center wire.
Throttle closed >200 milliVolts
Throttle wide open <4.8 Volts
As the throttle is moved between idle and WOT, the voltage
should smootly increase with no dropouts or jumps.

--
DougW