take a squirt bottle and spray all the plug wires while it's running and
look for arching
and if you are brave enough while the wires are wet and engine running
place both feet so they touch each other and touch the wires if you feel
current the wires are bad but jeep your feet together or you will get
poked real good clean the throttle body to see oif that improves idle

reboot wrote:

> '99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
> throttle (accelerating reasonably to 45 mph) the engine would start to
> stutter, hesitate and surge. water temperature gage shows the mid
> mark between cold and 210. when this happens and I open the throttle
> wide open it makes good power. on return to part throttle the
> hesitate and surge resumes. if i come to a stop while this is going
> on then the idle speed dips real low and sometimes stalls. runs very
> rough.
>
> if i drive it a few more minutes and get the water temperature all the
> way up it seems OK, smooth stable idle, smooth part throttle
> acceleration.
>
> in the first vista to the shop, they replaced the MAP sensor because
> it showed this code. took the truck back but the problem persisted.
>
> called the shop after this didn't fix the problem. they kept the
> truck overnight and tried it cold. didn't happen for them. they
> scanned the 'puter and no codes. they put in a set of plugs and
> replaced #6 spark plug wire because they said it looked corroded.
>
> told me drive it for a few weeks and call them back. if it fixed the
> problem we would discuss how much to pay for the 2nd visit. if it
> didn't ...
>
> so i've had the truck back a couple of weeks now and it happens pretty
> regularly. took it to Murray's this evening and hooked up a scanner -
> no codes, same as the shop with their good equipment and trained techs
> ...
>
> suggestions?
>
> reboot
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000778-2, 10/03/2007
> Tested on: 10/4/2007 12:14:28 AM
> avast! - copyright (c) 1988-2007 ALWIL Software.
> http://www.avast.com

 

On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:

>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>throttle (accelerating reasonably to 45 mph) the engine would start to
>stutter, hesitate and surge. water temperature gage shows the mid
>mark between cold and 210. when this happens and I open the throttle
>wide open it makes good power. on return to part throttle the
>hesitate and surge resumes. if i come to a stop while this is going
>on then the idle speed dips real low and sometimes stalls. runs very
>rough.
>
>if i drive it a few more minutes and get the water temperature all the
>way up it seems OK, smooth stable idle, smooth part throttle
>acceleration.
>
>in the first vista to the shop, they replaced the MAP sensor because
>it showed this code. took the truck back but the problem persisted.
>
>called the shop after this didn't fix the problem. they kept the
>truck overnight and tried it cold. didn't happen for them. they
>scanned the 'puter and no codes. they put in a set of plugs and
>replaced #6 spark plug wire because they said it looked corroded.
>
>told me drive it for a few weeks and call them back. if it fixed the
>problem we would discuss how much to pay for the 2nd visit. if it
>didn't ...
>
>so i've had the truck back a couple of weeks now and it happens pretty
>regularly. took it to Murray's this evening and hooked up a scanner -
>no codes, same as the shop with their good equipment and trained techs
>...
>
>suggestions?
>
>reboot

well folks, i've tried many of the suggestions made w/o any success.

i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
apart, cleaned both sides with QD Electronic Spray, blew them out w/
compressed air a re-assembled w/ dielectric silicone grease.

i had the throttle body off and cleaned it and took apart the IAC on
the side and cleaned it., staining but no blockage.

i checked the spark plug wires after dark with a spray bottle of water
and it looked good.

the driving experience when it hesitates and surges is like it
momentary runs below the lean limit for combustion. when it
hesitates, if I go to WOT it catches and pulls hard. no more
hesitation happens at WOT. but if i take it back to part throttle the
condition re-occurs.

from this I reason that the fuel rail pressure and injectors are OK -
if not then the problem would persist at WOT.

i also deduce that it isn't a spark problem because the load on the
ignition system is greater at WOT than part throttle and it runs fine
at WOT.

if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
they throw a code? in other words - can i have one of these sensors
bad and not find a code? (should i start back-probing them and
comparing the values to the FSM?)

damn - the wife is starting to doubt my wisdom in buying this jeep
because it was 'simple and easy to maintain and repair' (my previous
words which I'm beginning to doubt).

i;m reluctant to start swapping parts because of the expense and i
don't have confidence taking it back to the independent mechanic, they
couldn't find it before.

reboot

>
>---
>avast! Antivirus: Outbound message clean.
>Virus Database (VPS): 000778-2, 10/03/2007
>Tested on: 10/4/2007 12:14:28 AM
>avast! - copyright (c) 1988-2007 ALWIL Software.
>http://www.avast.com
>
>


---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 000778-5, 10/06/2007
Tested on: 10/7/2007 1:41:47 PM
avast! - copyright (c) 1988-2007 ALWIL Software.
http://www.avast.com

 

On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:

>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>throttle (accelerating reasonably to 45 mph) the engine would start to
>stutter, hesitate and surge. water temperature gage shows the mid
>mark between cold and 210. when this happens and I open the throttle
>wide open it makes good power. on return to part throttle the
>hesitate and surge resumes. if i come to a stop while this is going
>on then the idle speed dips real low and sometimes stalls. runs very
>rough.
>
>if i drive it a few more minutes and get the water temperature all the
>way up it seems OK, smooth stable idle, smooth part throttle
>acceleration.
>
>in the first vista to the shop, they replaced the MAP sensor because
>it showed this code. took the truck back but the problem persisted.
>
>called the shop after this didn't fix the problem. they kept the
>truck overnight and tried it cold. didn't happen for them. they
>scanned the 'puter and no codes. they put in a set of plugs and
>replaced #6 spark plug wire because they said it looked corroded.
>
>told me drive it for a few weeks and call them back. if it fixed the
>problem we would discuss how much to pay for the 2nd visit. if it
>didn't ...
>
>so i've had the truck back a couple of weeks now and it happens pretty
>regularly. took it to Murray's this evening and hooked up a scanner -
>no codes, same as the shop with their good equipment and trained techs
>...
>
>suggestions?
>
>reboot

well folks, i've tried many of the suggestions made w/o any success.

i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
apart, cleaned both sides with QD Electronic Spray, blew them out w/
compressed air a re-assembled w/ dielectric silicone grease.

i had the throttle body off and cleaned it and took apart the IAC on
the side and cleaned it., staining but no blockage.

i checked the spark plug wires after dark with a spray bottle of water
and it looked good.

the driving experience when it hesitates and surges is like it
momentary runs below the lean limit for combustion. when it
hesitates, if I go to WOT it catches and pulls hard. no more
hesitation happens at WOT. but if i take it back to part throttle the
condition re-occurs.

from this I reason that the fuel rail pressure and injectors are OK -
if not then the problem would persist at WOT.

i also deduce that it isn't a spark problem because the load on the
ignition system is greater at WOT than part throttle and it runs fine
at WOT.

if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
they throw a code? in other words - can i have one of these sensors
bad and not find a code? (should i start back-probing them and
comparing the values to the FSM?)

damn - the wife is starting to doubt my wisdom in buying this jeep
because it was 'simple and easy to maintain and repair' (my previous
words which I'm beginning to doubt).

i;m reluctant to start swapping parts because of the expense and i
don't have confidence taking it back to the independent mechanic, they
couldn't find it before.

reboot

>
>---
>avast! Antivirus: Outbound message clean.
>Virus Database (VPS): 000778-2, 10/03/2007
>Tested on: 10/4/2007 12:14:28 AM
>avast! - copyright (c) 1988-2007 ALWIL Software.
>http://www.avast.com
>
>


---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 000778-5, 10/06/2007
Tested on: 10/7/2007 1:41:47 PM
avast! - copyright (c) 1988-2007 ALWIL Software.
http://www.avast.com

 

On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:

>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>throttle (accelerating reasonably to 45 mph) the engine would start to
>stutter, hesitate and surge. water temperature gage shows the mid
>mark between cold and 210. when this happens and I open the throttle
>wide open it makes good power. on return to part throttle the
>hesitate and surge resumes. if i come to a stop while this is going
>on then the idle speed dips real low and sometimes stalls. runs very
>rough.
>
>if i drive it a few more minutes and get the water temperature all the
>way up it seems OK, smooth stable idle, smooth part throttle
>acceleration.
>
>in the first vista to the shop, they replaced the MAP sensor because
>it showed this code. took the truck back but the problem persisted.
>
>called the shop after this didn't fix the problem. they kept the
>truck overnight and tried it cold. didn't happen for them. they
>scanned the 'puter and no codes. they put in a set of plugs and
>replaced #6 spark plug wire because they said it looked corroded.
>
>told me drive it for a few weeks and call them back. if it fixed the
>problem we would discuss how much to pay for the 2nd visit. if it
>didn't ...
>
>so i've had the truck back a couple of weeks now and it happens pretty
>regularly. took it to Murray's this evening and hooked up a scanner -
>no codes, same as the shop with their good equipment and trained techs
>...
>
>suggestions?
>
>reboot

well folks, i've tried many of the suggestions made w/o any success.

i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
apart, cleaned both sides with QD Electronic Spray, blew them out w/
compressed air a re-assembled w/ dielectric silicone grease.

i had the throttle body off and cleaned it and took apart the IAC on
the side and cleaned it., staining but no blockage.

i checked the spark plug wires after dark with a spray bottle of water
and it looked good.

the driving experience when it hesitates and surges is like it
momentary runs below the lean limit for combustion. when it
hesitates, if I go to WOT it catches and pulls hard. no more
hesitation happens at WOT. but if i take it back to part throttle the
condition re-occurs.

from this I reason that the fuel rail pressure and injectors are OK -
if not then the problem would persist at WOT.

i also deduce that it isn't a spark problem because the load on the
ignition system is greater at WOT than part throttle and it runs fine
at WOT.

if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
they throw a code? in other words - can i have one of these sensors
bad and not find a code? (should i start back-probing them and
comparing the values to the FSM?)

damn - the wife is starting to doubt my wisdom in buying this jeep
because it was 'simple and easy to maintain and repair' (my previous
words which I'm beginning to doubt).

i;m reluctant to start swapping parts because of the expense and i
don't have confidence taking it back to the independent mechanic, they
couldn't find it before.

reboot

>
>---
>avast! Antivirus: Outbound message clean.
>Virus Database (VPS): 000778-2, 10/03/2007
>Tested on: 10/4/2007 12:14:28 AM
>avast! - copyright (c) 1988-2007 ALWIL Software.
>http://www.avast.com
>
>


---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 000778-5, 10/06/2007
Tested on: 10/7/2007 1:41:47 PM
avast! - copyright (c) 1988-2007 ALWIL Software.
http://www.avast.com

 

On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:

>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>throttle (accelerating reasonably to 45 mph) the engine would start to
>stutter, hesitate and surge. water temperature gage shows the mid
>mark between cold and 210. when this happens and I open the throttle
>wide open it makes good power. on return to part throttle the
>hesitate and surge resumes. if i come to a stop while this is going
>on then the idle speed dips real low and sometimes stalls. runs very
>rough.
>
>if i drive it a few more minutes and get the water temperature all the
>way up it seems OK, smooth stable idle, smooth part throttle
>acceleration.
>
>in the first vista to the shop, they replaced the MAP sensor because
>it showed this code. took the truck back but the problem persisted.
>
>called the shop after this didn't fix the problem. they kept the
>truck overnight and tried it cold. didn't happen for them. they
>scanned the 'puter and no codes. they put in a set of plugs and
>replaced #6 spark plug wire because they said it looked corroded.
>
>told me drive it for a few weeks and call them back. if it fixed the
>problem we would discuss how much to pay for the 2nd visit. if it
>didn't ...
>
>so i've had the truck back a couple of weeks now and it happens pretty
>regularly. took it to Murray's this evening and hooked up a scanner -
>no codes, same as the shop with their good equipment and trained techs
>...
>
>suggestions?
>
>reboot

well folks, i've tried many of the suggestions made w/o any success.

i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
apart, cleaned both sides with QD Electronic Spray, blew them out w/
compressed air a re-assembled w/ dielectric silicone grease.

i had the throttle body off and cleaned it and took apart the IAC on
the side and cleaned it., staining but no blockage.

i checked the spark plug wires after dark with a spray bottle of water
and it looked good.

the driving experience when it hesitates and surges is like it
momentary runs below the lean limit for combustion. when it
hesitates, if I go to WOT it catches and pulls hard. no more
hesitation happens at WOT. but if i take it back to part throttle the
condition re-occurs.

from this I reason that the fuel rail pressure and injectors are OK -
if not then the problem would persist at WOT.

i also deduce that it isn't a spark problem because the load on the
ignition system is greater at WOT than part throttle and it runs fine
at WOT.

if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
they throw a code? in other words - can i have one of these sensors
bad and not find a code? (should i start back-probing them and
comparing the values to the FSM?)

damn - the wife is starting to doubt my wisdom in buying this jeep
because it was 'simple and easy to maintain and repair' (my previous
words which I'm beginning to doubt).

i;m reluctant to start swapping parts because of the expense and i
don't have confidence taking it back to the independent mechanic, they
couldn't find it before.

reboot

>
>---
>avast! Antivirus: Outbound message clean.
>Virus Database (VPS): 000778-2, 10/03/2007
>Tested on: 10/4/2007 12:14:28 AM
>avast! - copyright (c) 1988-2007 ALWIL Software.
>http://www.avast.com
>
>


---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 000778-5, 10/06/2007
Tested on: 10/7/2007 1:41:47 PM
avast! - copyright (c) 1988-2007 ALWIL Software.
http://www.avast.com

 

THis might sound crazy, but i had a similar problem with my CJ. I has a 4.0
head and MPFI. on cool mornings it would do the saem thing you describe
until warmed up. By luck I had to remove the exhaust manifold to take care
on another issue and when I put it back together everything ran fine. A few
months later it started the cold stumble again. I remembered the manifold
incident, so I removed it once more checked it for flatness across the
flange and found it to be a bit out. Not much but enought to not get a
perfect seal against the cylinder head. I had the exhaust manifold surfaced,
and put a new exhaust gasket on... my troubles disappeared.
I figure, the slight leak, whan cold allowed fresh air into the exhaust that
threw off the O2 sensor reading making it rev then stumble...
Worth checking into

--
Rich Harris

"reboot" <reboot@nothere.com> wrote in message
news:8o5ig3l1r7ivgsv7qd2lgphcc113dh4if8@4ax.com...
> On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:
>
>>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>>throttle (accelerating reasonably to 45 mph) the engine would start to
>>stutter, hesitate and surge. water temperature gage shows the mid
>>mark between cold and 210. when this happens and I open the throttle
>>wide open it makes good power. on return to part throttle the
>>hesitate and surge resumes. if i come to a stop while this is going
>>on then the idle speed dips real low and sometimes stalls. runs very
>>rough.
>>
>>if i drive it a few more minutes and get the water temperature all the
>>way up it seems OK, smooth stable idle, smooth part throttle
>>acceleration.
>>
>>in the first vista to the shop, they replaced the MAP sensor because
>>it showed this code. took the truck back but the problem persisted.
>>
>>called the shop after this didn't fix the problem. they kept the
>>truck overnight and tried it cold. didn't happen for them. they
>>scanned the 'puter and no codes. they put in a set of plugs and
>>replaced #6 spark plug wire because they said it looked corroded.
>>
>>told me drive it for a few weeks and call them back. if it fixed the
>>problem we would discuss how much to pay for the 2nd visit. if it
>>didn't ...
>>
>>so i've had the truck back a couple of weeks now and it happens pretty
>>regularly. took it to Murray's this evening and hooked up a scanner -
>>no codes, same as the shop with their good equipment and trained techs
>>...
>>
>>suggestions?
>>
>>reboot
>
> well folks, i've tried many of the suggestions made w/o any success.
>
> i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
> apart, cleaned both sides with QD Electronic Spray, blew them out w/
> compressed air a re-assembled w/ dielectric silicone grease.
>
> i had the throttle body off and cleaned it and took apart the IAC on
> the side and cleaned it., staining but no blockage.
>
> i checked the spark plug wires after dark with a spray bottle of water
> and it looked good.
>
> the driving experience when it hesitates and surges is like it
> momentary runs below the lean limit for combustion. when it
> hesitates, if I go to WOT it catches and pulls hard. no more
> hesitation happens at WOT. but if i take it back to part throttle the
> condition re-occurs.
>
> from this I reason that the fuel rail pressure and injectors are OK -
> if not then the problem would persist at WOT.
>
> i also deduce that it isn't a spark problem because the load on the
> ignition system is greater at WOT than part throttle and it runs fine
> at WOT.
>
> if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
> they throw a code? in other words - can i have one of these sensors
> bad and not find a code? (should i start back-probing them and
> comparing the values to the FSM?)
>
> damn - the wife is starting to doubt my wisdom in buying this jeep
> because it was 'simple and easy to maintain and repair' (my previous
> words which I'm beginning to doubt).
>
> i;m reluctant to start swapping parts because of the expense and i
> don't have confidence taking it back to the independent mechanic, they
> couldn't find it before.
>
> reboot
>
>>
>>---
>>avast! Antivirus: Outbound message clean.
>>Virus Database (VPS): 000778-2, 10/03/2007
>>Tested on: 10/4/2007 12:14:28 AM
>>avast! - copyright (c) 1988-2007 ALWIL Software.
>>http://www.avast.com
>>
>>
>
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000778-5, 10/06/2007
> Tested on: 10/7/2007 1:41:47 PM
> avast! - copyright (c) 1988-2007 ALWIL Software.
> http://www.avast.com
>
>
>

 

THis might sound crazy, but i had a similar problem with my CJ. I has a 4.0
head and MPFI. on cool mornings it would do the saem thing you describe
until warmed up. By luck I had to remove the exhaust manifold to take care
on another issue and when I put it back together everything ran fine. A few
months later it started the cold stumble again. I remembered the manifold
incident, so I removed it once more checked it for flatness across the
flange and found it to be a bit out. Not much but enought to not get a
perfect seal against the cylinder head. I had the exhaust manifold surfaced,
and put a new exhaust gasket on... my troubles disappeared.
I figure, the slight leak, whan cold allowed fresh air into the exhaust that
threw off the O2 sensor reading making it rev then stumble...
Worth checking into

--
Rich Harris

"reboot" <reboot@nothere.com> wrote in message
news:8o5ig3l1r7ivgsv7qd2lgphcc113dh4if8@4ax.com...
> On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:
>
>>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>>throttle (accelerating reasonably to 45 mph) the engine would start to
>>stutter, hesitate and surge. water temperature gage shows the mid
>>mark between cold and 210. when this happens and I open the throttle
>>wide open it makes good power. on return to part throttle the
>>hesitate and surge resumes. if i come to a stop while this is going
>>on then the idle speed dips real low and sometimes stalls. runs very
>>rough.
>>
>>if i drive it a few more minutes and get the water temperature all the
>>way up it seems OK, smooth stable idle, smooth part throttle
>>acceleration.
>>
>>in the first vista to the shop, they replaced the MAP sensor because
>>it showed this code. took the truck back but the problem persisted.
>>
>>called the shop after this didn't fix the problem. they kept the
>>truck overnight and tried it cold. didn't happen for them. they
>>scanned the 'puter and no codes. they put in a set of plugs and
>>replaced #6 spark plug wire because they said it looked corroded.
>>
>>told me drive it for a few weeks and call them back. if it fixed the
>>problem we would discuss how much to pay for the 2nd visit. if it
>>didn't ...
>>
>>so i've had the truck back a couple of weeks now and it happens pretty
>>regularly. took it to Murray's this evening and hooked up a scanner -
>>no codes, same as the shop with their good equipment and trained techs
>>...
>>
>>suggestions?
>>
>>reboot
>
> well folks, i've tried many of the suggestions made w/o any success.
>
> i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
> apart, cleaned both sides with QD Electronic Spray, blew them out w/
> compressed air a re-assembled w/ dielectric silicone grease.
>
> i had the throttle body off and cleaned it and took apart the IAC on
> the side and cleaned it., staining but no blockage.
>
> i checked the spark plug wires after dark with a spray bottle of water
> and it looked good.
>
> the driving experience when it hesitates and surges is like it
> momentary runs below the lean limit for combustion. when it
> hesitates, if I go to WOT it catches and pulls hard. no more
> hesitation happens at WOT. but if i take it back to part throttle the
> condition re-occurs.
>
> from this I reason that the fuel rail pressure and injectors are OK -
> if not then the problem would persist at WOT.
>
> i also deduce that it isn't a spark problem because the load on the
> ignition system is greater at WOT than part throttle and it runs fine
> at WOT.
>
> if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
> they throw a code? in other words - can i have one of these sensors
> bad and not find a code? (should i start back-probing them and
> comparing the values to the FSM?)
>
> damn - the wife is starting to doubt my wisdom in buying this jeep
> because it was 'simple and easy to maintain and repair' (my previous
> words which I'm beginning to doubt).
>
> i;m reluctant to start swapping parts because of the expense and i
> don't have confidence taking it back to the independent mechanic, they
> couldn't find it before.
>
> reboot
>
>>
>>---
>>avast! Antivirus: Outbound message clean.
>>Virus Database (VPS): 000778-2, 10/03/2007
>>Tested on: 10/4/2007 12:14:28 AM
>>avast! - copyright (c) 1988-2007 ALWIL Software.
>>http://www.avast.com
>>
>>
>
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000778-5, 10/06/2007
> Tested on: 10/7/2007 1:41:47 PM
> avast! - copyright (c) 1988-2007 ALWIL Software.
> http://www.avast.com
>
>
>

 

THis might sound crazy, but i had a similar problem with my CJ. I has a 4.0
head and MPFI. on cool mornings it would do the saem thing you describe
until warmed up. By luck I had to remove the exhaust manifold to take care
on another issue and when I put it back together everything ran fine. A few
months later it started the cold stumble again. I remembered the manifold
incident, so I removed it once more checked it for flatness across the
flange and found it to be a bit out. Not much but enought to not get a
perfect seal against the cylinder head. I had the exhaust manifold surfaced,
and put a new exhaust gasket on... my troubles disappeared.
I figure, the slight leak, whan cold allowed fresh air into the exhaust that
threw off the O2 sensor reading making it rev then stumble...
Worth checking into

--
Rich Harris

"reboot" <reboot@nothere.com> wrote in message
news:8o5ig3l1r7ivgsv7qd2lgphcc113dh4if8@4ax.com...
> On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:
>
>>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>>throttle (accelerating reasonably to 45 mph) the engine would start to
>>stutter, hesitate and surge. water temperature gage shows the mid
>>mark between cold and 210. when this happens and I open the throttle
>>wide open it makes good power. on return to part throttle the
>>hesitate and surge resumes. if i come to a stop while this is going
>>on then the idle speed dips real low and sometimes stalls. runs very
>>rough.
>>
>>if i drive it a few more minutes and get the water temperature all the
>>way up it seems OK, smooth stable idle, smooth part throttle
>>acceleration.
>>
>>in the first vista to the shop, they replaced the MAP sensor because
>>it showed this code. took the truck back but the problem persisted.
>>
>>called the shop after this didn't fix the problem. they kept the
>>truck overnight and tried it cold. didn't happen for them. they
>>scanned the 'puter and no codes. they put in a set of plugs and
>>replaced #6 spark plug wire because they said it looked corroded.
>>
>>told me drive it for a few weeks and call them back. if it fixed the
>>problem we would discuss how much to pay for the 2nd visit. if it
>>didn't ...
>>
>>so i've had the truck back a couple of weeks now and it happens pretty
>>regularly. took it to Murray's this evening and hooked up a scanner -
>>no codes, same as the shop with their good equipment and trained techs
>>...
>>
>>suggestions?
>>
>>reboot
>
> well folks, i've tried many of the suggestions made w/o any success.
>
> i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
> apart, cleaned both sides with QD Electronic Spray, blew them out w/
> compressed air a re-assembled w/ dielectric silicone grease.
>
> i had the throttle body off and cleaned it and took apart the IAC on
> the side and cleaned it., staining but no blockage.
>
> i checked the spark plug wires after dark with a spray bottle of water
> and it looked good.
>
> the driving experience when it hesitates and surges is like it
> momentary runs below the lean limit for combustion. when it
> hesitates, if I go to WOT it catches and pulls hard. no more
> hesitation happens at WOT. but if i take it back to part throttle the
> condition re-occurs.
>
> from this I reason that the fuel rail pressure and injectors are OK -
> if not then the problem would persist at WOT.
>
> i also deduce that it isn't a spark problem because the load on the
> ignition system is greater at WOT than part throttle and it runs fine
> at WOT.
>
> if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
> they throw a code? in other words - can i have one of these sensors
> bad and not find a code? (should i start back-probing them and
> comparing the values to the FSM?)
>
> damn - the wife is starting to doubt my wisdom in buying this jeep
> because it was 'simple and easy to maintain and repair' (my previous
> words which I'm beginning to doubt).
>
> i;m reluctant to start swapping parts because of the expense and i
> don't have confidence taking it back to the independent mechanic, they
> couldn't find it before.
>
> reboot
>
>>
>>---
>>avast! Antivirus: Outbound message clean.
>>Virus Database (VPS): 000778-2, 10/03/2007
>>Tested on: 10/4/2007 12:14:28 AM
>>avast! - copyright (c) 1988-2007 ALWIL Software.
>>http://www.avast.com
>>
>>
>
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000778-5, 10/06/2007
> Tested on: 10/7/2007 1:41:47 PM
> avast! - copyright (c) 1988-2007 ALWIL Software.
> http://www.avast.com
>
>
>

 

THis might sound crazy, but i had a similar problem with my CJ. I has a 4.0
head and MPFI. on cool mornings it would do the saem thing you describe
until warmed up. By luck I had to remove the exhaust manifold to take care
on another issue and when I put it back together everything ran fine. A few
months later it started the cold stumble again. I remembered the manifold
incident, so I removed it once more checked it for flatness across the
flange and found it to be a bit out. Not much but enought to not get a
perfect seal against the cylinder head. I had the exhaust manifold surfaced,
and put a new exhaust gasket on... my troubles disappeared.
I figure, the slight leak, whan cold allowed fresh air into the exhaust that
threw off the O2 sensor reading making it rev then stumble...
Worth checking into

--
Rich Harris

"reboot" <reboot@nothere.com> wrote in message
news:8o5ig3l1r7ivgsv7qd2lgphcc113dh4if8@4ax.com...
> On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:
>
>>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
>>throttle (accelerating reasonably to 45 mph) the engine would start to
>>stutter, hesitate and surge. water temperature gage shows the mid
>>mark between cold and 210. when this happens and I open the throttle
>>wide open it makes good power. on return to part throttle the
>>hesitate and surge resumes. if i come to a stop while this is going
>>on then the idle speed dips real low and sometimes stalls. runs very
>>rough.
>>
>>if i drive it a few more minutes and get the water temperature all the
>>way up it seems OK, smooth stable idle, smooth part throttle
>>acceleration.
>>
>>in the first vista to the shop, they replaced the MAP sensor because
>>it showed this code. took the truck back but the problem persisted.
>>
>>called the shop after this didn't fix the problem. they kept the
>>truck overnight and tried it cold. didn't happen for them. they
>>scanned the 'puter and no codes. they put in a set of plugs and
>>replaced #6 spark plug wire because they said it looked corroded.
>>
>>told me drive it for a few weeks and call them back. if it fixed the
>>problem we would discuss how much to pay for the 2nd visit. if it
>>didn't ...
>>
>>so i've had the truck back a couple of weeks now and it happens pretty
>>regularly. took it to Murray's this evening and hooked up a scanner -
>>no codes, same as the shop with their good equipment and trained techs
>>...
>>
>>suggestions?
>>
>>reboot
>
> well folks, i've tried many of the suggestions made w/o any success.
>
> i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
> apart, cleaned both sides with QD Electronic Spray, blew them out w/
> compressed air a re-assembled w/ dielectric silicone grease.
>
> i had the throttle body off and cleaned it and took apart the IAC on
> the side and cleaned it., staining but no blockage.
>
> i checked the spark plug wires after dark with a spray bottle of water
> and it looked good.
>
> the driving experience when it hesitates and surges is like it
> momentary runs below the lean limit for combustion. when it
> hesitates, if I go to WOT it catches and pulls hard. no more
> hesitation happens at WOT. but if i take it back to part throttle the
> condition re-occurs.
>
> from this I reason that the fuel rail pressure and injectors are OK -
> if not then the problem would persist at WOT.
>
> i also deduce that it isn't a spark problem because the load on the
> ignition system is greater at WOT than part throttle and it runs fine
> at WOT.
>
> if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
> they throw a code? in other words - can i have one of these sensors
> bad and not find a code? (should i start back-probing them and
> comparing the values to the FSM?)
>
> damn - the wife is starting to doubt my wisdom in buying this jeep
> because it was 'simple and easy to maintain and repair' (my previous
> words which I'm beginning to doubt).
>
> i;m reluctant to start swapping parts because of the expense and i
> don't have confidence taking it back to the independent mechanic, they
> couldn't find it before.
>
> reboot
>
>>
>>---
>>avast! Antivirus: Outbound message clean.
>>Virus Database (VPS): 000778-2, 10/03/2007
>>Tested on: 10/4/2007 12:14:28 AM
>>avast! - copyright (c) 1988-2007 ALWIL Software.
>>http://www.avast.com
>>
>>
>
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000778-5, 10/06/2007
> Tested on: 10/7/2007 1:41:47 PM
> avast! - copyright (c) 1988-2007 ALWIL Software.
> http://www.avast.com
>
>
>

 

need to hook up a fuel pressure gauge and see if it running at spec and has
volume it should also not blow any bubbles into a clear container

Rich wrote:

> THis might sound crazy, but i had a similar problem with my CJ. I has a 4.0
> head and MPFI. on cool mornings it would do the saem thing you describe
> until warmed up. By luck I had to remove the exhaust manifold to take care
> on another issue and when I put it back together everything ran fine. A few
> months later it started the cold stumble again. I remembered the manifold
> incident, so I removed it once more checked it for flatness across the
> flange and found it to be a bit out. Not much but enought to not get a
> perfect seal against the cylinder head. I had the exhaust manifold surfaced,
> and put a new exhaust gasket on... my troubles disappeared.
> I figure, the slight leak, whan cold allowed fresh air into the exhaust that
> threw off the O2 sensor reading making it rev then stumble...
> Worth checking into
>
> --
> Rich Harris
>
> "reboot" <reboot@nothere.com> wrote in message
> news:8o5ig3l1r7ivgsv7qd2lgphcc113dh4if8@4ax.com...
> > On Thu, 04 Oct 2007 00:14:27 -0400, reboot <reboot@nothere.com> wrote:
> >
> >>'99 TJ 4.0 Auto - within about 3 minutes of a cold start under part
> >>throttle (accelerating reasonably to 45 mph) the engine would start to
> >>stutter, hesitate and surge. water temperature gage shows the mid
> >>mark between cold and 210. when this happens and I open the throttle
> >>wide open it makes good power. on return to part throttle the
> >>hesitate and surge resumes. if i come to a stop while this is going
> >>on then the idle speed dips real low and sometimes stalls. runs very
> >>rough.
> >>
> >>if i drive it a few more minutes and get the water temperature all the
> >>way up it seems OK, smooth stable idle, smooth part throttle
> >>acceleration.
> >>
> >>in the first vista to the shop, they replaced the MAP sensor because
> >>it showed this code. took the truck back but the problem persisted.
> >>
> >>called the shop after this didn't fix the problem. they kept the
> >>truck overnight and tried it cold. didn't happen for them. they
> >>scanned the 'puter and no codes. they put in a set of plugs and
> >>replaced #6 spark plug wire because they said it looked corroded.
> >>
> >>told me drive it for a few weeks and call them back. if it fixed the
> >>problem we would discuss how much to pay for the 2nd visit. if it
> >>didn't ...
> >>
> >>so i've had the truck back a couple of weeks now and it happens pretty
> >>regularly. took it to Murray's this evening and hooked up a scanner -
> >>no codes, same as the shop with their good equipment and trained techs
> >>...
> >>
> >>suggestions?
> >>
> >>reboot
> >
> > well folks, i've tried many of the suggestions made w/o any success.
> >
> > i had all of the TSB / IAC / MAP / CPS and IAT electrical connectors
> > apart, cleaned both sides with QD Electronic Spray, blew them out w/
> > compressed air a re-assembled w/ dielectric silicone grease.
> >
> > i had the throttle body off and cleaned it and took apart the IAC on
> > the side and cleaned it., staining but no blockage.
> >
> > i checked the spark plug wires after dark with a spray bottle of water
> > and it looked good.
> >
> > the driving experience when it hesitates and surges is like it
> > momentary runs below the lean limit for combustion. when it
> > hesitates, if I go to WOT it catches and pulls hard. no more
> > hesitation happens at WOT. but if i take it back to part throttle the
> > condition re-occurs.
> >
> > from this I reason that the fuel rail pressure and injectors are OK -
> > if not then the problem would persist at WOT.
> >
> > i also deduce that it isn't a spark problem because the load on the
> > ignition system is greater at WOT than part throttle and it runs fine
> > at WOT.
> >
> > if there is any problem with the TPS/MAP/IAT/IAC/CPS sensors would
> > they throw a code? in other words - can i have one of these sensors
> > bad and not find a code? (should i start back-probing them and
> > comparing the values to the FSM?)
> >
> > damn - the wife is starting to doubt my wisdom in buying this jeep
> > because it was 'simple and easy to maintain and repair' (my previous
> > words which I'm beginning to doubt).
> >
> > i;m reluctant to start swapping parts because of the expense and i
> > don't have confidence taking it back to the independent mechanic, they
> > couldn't find it before.
> >
> > reboot
> >
> >>
> >>---
> >>avast! Antivirus: Outbound message clean.
> >>Virus Database (VPS): 000778-2, 10/03/2007
> >>Tested on: 10/4/2007 12:14:28 AM
> >>avast! - copyright (c) 1988-2007 ALWIL Software.
> >>http://www.avast.com
> >>
> >>
> >
> >
> > ---
> > avast! Antivirus: Outbound message clean.
> > Virus Database (VPS): 000778-5, 10/06/2007
> > Tested on: 10/7/2007 1:41:47 PM
> > avast! - copyright (c) 1988-2007 ALWIL Software.
> > http://www.avast.com
> >
> >
> >