Topic: Bad hesitation when cold

[little97tj]

 

 Everytime I start my jeep it has a bad hesitation untill it warms up, It will actually run fine untill a curtain point then the motor will start to stuble sounds like it has a huge cam at idea "kind of cool sounding" anyhow if you try to drive it at this point it has no power and falls on its face. On the other hand if you hold it to the flooor it will drive threw it and then be fine.

I've been dealing with this issue for a while but jeep only gets off roaded for the most part, I switched to a 4.0 throtle body at one point thinking it might help but probem remained the same. I left all the sensors on the 4.0 throttle body like i said problem was the same no better of no worse

Jeep has 105k on it, was thinking Id try and sort this out before the holiday weekend... anyone else seen this problem? I seen other post that sounded the same but no solutions

[lanulos89]

missfire, dumping fuel then clears up nd drives fine

[little97tj]

 

That would be the animal

[Shadowman890]

I'm having a similar issue, but here's a little back story. When I had about 20,000 miles on my Jeep, it developed a bad stalling/loss of power, not just at idle but also randomly while driving. It wound up getting so bad that it just had zero power all the time and I finally got my dealership to take a look at it. It wound up being that the Cat was clogged. As soon as they replaced it, the problem went away for about 5,000 miles then it kinda started again but I got a check engine light this time. This time I had a bad spark plug, I replaced all the plugs and wires and it ran better then it ever did. Now i have around 47,000 miles and this whole thing is starting again, but this time there is no check engine light and plenty of backpressure in the exhaust so it's not the cat, are my plugs just bad again, even though I put Iridium plugs in last time?

[Steve-0]

I have read this thread over and over again and I havent gotten a good conclusion. I also have a stumble when cold but can power through it until it warms up. Not too big of a deal, but would be nice if it wasnt there. Anyway, I have the hesitation or stumbling at around 2300 - 2800 RPM. It is sporadic and at times feels like it stalled when I am on the freeway but it stays alive. That doesnt happen to often, but I am concerned about the stumbling around this RPM range. I tested the TPS and it tested out fine. When I did the 4.0 TB conversion, the AIS was real cruddy and I cleaned it off but never done that before so I didnt want to spin it around and mess anything up. Put it all together with the old 2.5 AIS housing and its great. throttle response is much quicker. Can anyone help with the stumbling problem? I was about to unplug the O2 and see if that helps or it could be something else because after cleaning the AIS, my choke dosent stay up for more than 2-3 seconds in the morning. Vacuum leak? Dont get it. Thanks.

[sharpxmen]

you might want to check the temp sensor for the PCM, that can cause the idle to be too low at cold and not get enough fuel either - can't say it's 100% that but give it a shot.

[Steve-0]

Ok, I was able to narrow the REAL bad stutter area. At 2800 RPM and the RPMs drop all of a sudden to about 1900 or so, like a hickup. But I can do it every time at that RPM range. Other than that REAL bad spot, it does it from around 2200 RPMs to 2800 here and there but not too bad, but still annoying. No codes were pulled (accept the Ac code of course). I thought it was the TPS as my 4Runner (auto) had the shifting between 3-4-5 back and fourth, but mostly 4-5 on the freeway. I replaced it and it helped quite a bit, but still did it every once in a while. But I pulled the TPS on the Jeep and it tested out fine. Also, when I got the 4.0 TB I took out all the sensors. The TPS from the 4.0, will it work on the 2.5? There is a #1 on the 2.5 and a #2 I believe on the 4.0 TB near the part number. They both tested fine, but can I use the TPS from the 4.0 and see if that helps before I buy a new TPS? Or do I need to look somewhere else for the solution?

[sharpxmen]

Ok, I was able to narrow the REAL bad stutter area. At 2800 RPM and the RPMs drop all of a sudden to about 1900 or so, like a hickup. But I can do it every time at that RPM range. Other than that REAL bad spot, it does it from around 2200 RPMs to 2800 here and there but not too bad, but still annoying. No codes were pulled (accept the Ac code of course). I thought it was the TPS as my 4Runner (auto) had the shifting between 3-4-5 back and fourth, but mostly 4-5 on the freeway. I replaced it and it helped quite a bit, but still did it every once in a while. But I pulled the TPS on the Jeep and it tested out fine. Also, when I got the 4.0 TB I took out all the sensors. The TPS from the 4.0, will it work on the 2.5? There is a #1 on the 2.5 and a #2 I believe on the 4.0 TB near the part number. They both tested fine, but can I use the TPS from the 4.0 and see if that helps before I buy a new TPS? Or do I need to look somewhere else for the solution?

you can't use the 4.0 tps, P/Ns are different so it will give different info to the PCM. Related to no high idle when cold most obvious can be the IAC (also known as AIS) or the temp sensor that i mentioned before. For the hesitation at a specific RPM (and this is assuming that is not at a specific TPS position, in which case would point to the TPS) - could be ignition/spark related - i would inspect the distrib cap/rotor, the wires and plugs, hopefully is one of those - If not could be crank sensor, cam sensor, MAP or even TPS but would be hard to narrow down unless you have a way to "certify" each one individually.

[Steve-0]

I think I am going to just get another TPS and see if that helps. That seems to be the direction I am leaning and it makes the most sense. If it doesnt work, oh well, its not hard to replace and I can just return it. Since it IS at a specific RPM range, (now i think it is at 2500 RPM) its got to be the TPS. I will also try to replace the AIS and report my findings.

[Steve-0]

This is confusing me. Originally the "bad spot" was around 2800 RPM and then lowered to 2500 RPM and now it seems like it may have either moved to 2200 RPM and/or the "hick-up" has stopped. Now it just has a slight rough spot. I don't get it. Do you think this has anything to do with the 4.0l throttle body and spacer I recently put on? Again, I noticed that the TPS, when I took it off the 2.5 and put it on the 4.0 it was a bit dirty, but I didnt see what good a cleaning would do to it since it is pretty much a sealed component, so i left it alone. The AIS was real nasty and I just whiped it down with a rag and carb cleaner. I didnt see any dirt/grime that could have come loose from the AIS to mess with the system but I didnt really clean the inside of the AIS housing from the 2.5 when I swapped it all. So far it seems like the RPM drop has been eliminated for some reason but I can still feel a rough spot around 2200 to 2500 RPM, but it is very hard to feel since the thing gets blown around in the wind so easily. Any ideas? Thanks.

[dwtaylorpdx]

When I put the 4.0 TB on my YJ the TPS failed, then just so the jeep gods could
really laugh, I got a bad one in the box
The 3rd time was the charm, I HIGHLY recommend spending the extra dough on
the one from NAPA not Autozone.
If you saw them both taken apart its apparent that one is better quality.....


Dave

[Steve-0]

So were you having the stumbling effect that I am having now? I only had a TPS go bad in a 4Runner and it was an automatic so it would shift erratically. So I wasnt too sure about a TPS in a 5 speed.

[dwtaylorpdx]

It would cough and buck, power would go away, sometime get a little tail pipe pop...
sometimes you could drive through it by flooring the pedal fast.

I finally decided it was the TPS because there was a spot that if
I backed down real slow under load it would stumble just a tad.
It was way worse on the cold engine.

[Steve-0]

Ok, replaced the TPS and it still has the same effects. I guess I need to try a few other sensors and see if that helps. Keep doing that until the stumbling stops. Again, its mostly a slight stumble. Almost feels like when you get a strong headwind hitting you, but its not that for sure. Its not like the bucking you'd get if you were running out of gas (know that feeling too well). I need to go back in this thread and look for the other culprit sensors. I think they were, AIS, O2, crank position and temp sensor right?

[Jesse-James]

Did you ever pull codes on it? I would do that at least before replacing random sensors.