jeep issue need help diagnosing

[madness410]

hey everyone i know this isnt a jeep forum but everyone here always offers great information. im a member of jeep forum and from what ive seen if you post an issue on there they either refer you back to the common problem threads or you'll be left with probably 30 different reasons why your jeep is screwing up.

anyways...got my jeep back from the shop today for some rear end work, make it home fine. taking it around for a test drive after it stalls. starts back up if i hit the gas a little bit while turning the key. driving around more, it gets worse. if i rev the engine to 2.5k in park, the rpm needle will just come straight down to 0 and stall. start it back up again it fires up with a little foot on the gas, drive around mess around with some electronics like flip the heat all the way on...it stalls again lol. that was weird im not sure why it did that. sometimes also the rpm needle after i hit the gas goes from .5k to 1k back to .5k.

im thinking its a fuel issue...since i got it i havent done anything with the fuel system. if anyone thinks its anything different let me know. either way i can guarantee it could benefit from a new filter or at the very least some fuel injector cleaner. are there any tell tale signs of the fuel pump about to take a crap? any input would be great guys thanks a lot.

Jon

[The_Bishop]

Is this a 4.0 jeep? Might be the crank position sensor.

[madness410]

5.2...yeah ive been reading on that too on jeep forum. seems like everyone there will add in their .02 of what it can be and at the end of the thread you'll have 30 reasons why your car is acting up lol.

[greenformula92]

Any codes?

[madness410]

the check engine light isnt on...i do have a scanner tool i could plug in but currently my brother has it. ill check tomorrow.

[BullittSVT]

Couple common problems I've heard, the TPS.. the IAC... I've had my jeep do this to me for a few days, I swapped out the battery and IAC and strangely enough it hasnt done it to me in a couple days.. probably just the stupid sensors.

[The_Bishop]

If I have it right, you're saying that the tach is reading incorrectly right before it stalls, right? That's why I mentioned the CPS. Not completely a shot in the dark, but the best I can do with the limited info available.

[madness410]

Couple common problems I've heard, the TPS.. the IAC... I've had my jeep do this to me for a few days, I swapped out the battery and IAC and strangely enough it hasnt done it to me in a couple days.. probably just the stupid sensors.

yeah ive heard those also. ill check those out tomorrow make sure they arent loose or corroded.

If I have it right, you're saying that the tach is reading incorrectly right before it stalls, right? That's why I mentioned the CPS. Not completely a shot in the dark, but the best I can do with the limited info available.

nope the tach reads fine. it just shows how the motor is before it stalls. if i revved the motor up the 2.5k it would come straight back down to 0, stalling.

its weird though i took it for two separate rides after that and now it works fine. although sometimes it still seems like the rpms dip way under what they should, barely not stalling.

[madness410]

yup problems back lol.

[The_Bishop]

Ok, did you do this? -
http://www.jeepforum.com/forum/f13/how-clean-your-idle-air-control-valve-756934/

Or replace it. Whatever floats your boat/makes your wallet happy. Also clean out the hole it mates into.

And afterwards disconnect your battery for 10-20 minutes to reset the PCM and let it re-learn the idle.

Fixed this for someone else a few years back and forgot all about it.

[madness410]

yeah thats the exact thread i was looking out yesterday. i didnt clean it though i replaced it completely...it was only 45 for a replacement. i didnt reset the pcm though ill go outside to reset it now. but it was still idling a bit funny and low when in park, when switched to neutral reverse or drive the rpms still fluctuated. not sure if thats normal but it was doing the same thing yesterday. however driving around i probably put 5-10 miles on it with the replacement it didnt even come close to stalling.

[B4C]

The way its acting, what you described. Being able to start it with ur foot on the gas and it stalling when u take it off, its the IAC

[madness410]

yes i replaced the iac the other day. i havent really had much of a chance to take it out for normal daily driving to see how it is...but i will take it out today and see how it goes. thanks for the input.

[madness410]

cleaned the iac and seems to work much better. hasnt stalled on me once. but now i think i have a trans problem. idk what it is

driving on the highway today at around 50-60 mph, i was just cruising not flooring it, at around 3k rpm, seems like it should have shifted into 4th but didnt. during normal driving around town, shifts through all the gears just fine but 3rd and 4th on the highway seem a little weird.

another thing is if i would let my foot off the gas completely it would stay at around 2-2.5k rpm and not drop down to idle.

when i got home i had the parts to do a transmission fluid change, which i did. checked in the pan after it was removed and it was clean, not even a splinter of metal in there. idk if its the trans acting up or if its another bad sensor or something.

[NastyEllEssWon]

i know this sounds so simple, but mostly whenever you do any type of work its common place to unhook the battery while working on it. im not familiar with these jeeps but i would take a shot with unhooking the battery and doing an idle relearn on it. it kinda reminds me of when i was young and was screwing around with my beretta. it did the same exact thing.

[GhostDakota]

i know this sounds so simple, but mostly whenever you do any type of work its common place to unhook the battery while working on it. im not familiar with these jeeps but i would take a shot with unhooking the battery and doing an idle relearn on it. it kinda reminds me of when i was young and was screwing around with my beretta. it did the same exact thing.

Typically a Jeep ECU reset:

1. Disconnect the battery by removing the positive battery cable. Remember, the positive battery cable.
2. Ground the positive cable to the negative cable for 30 seconds to erase the electric charge in the capacitors.
3. Reconnect the positive cable to the battery.
4. Turn the key to on but do not start.
5. Turn the headlights on.
6. Turn the headlights off.
7. Turn the key off.
The ECU has been reset to factory conditions. For the first 50 warm-up periods the ECU will re-learn the engine and driving habits for your driving conditions and the newly installed parts.