Hey all.. Let me say first off, my problem is quite similar to the following post:
http://www.automotiveforums.com/vbulletin/showthread.php?t=958737

I didn't post/reply to that because it's not the EXACT same and I didn't want to hijack! :)

On my Jeep, after running maybe a minute or 2, once you give it some gas, it'll dive back down below "normal" idle and either stall itself out or give me a good scare that it's going to. After that first minute'ish, it does it every time.

A friend suggested to me to disconnect the battery to reset the ECU (let the Jeep get it's air/fuel mixture reset essentially). That actually SEEMED to work once, but then a few days later the problem resumed. Tried it again, and didn't seem to be as effective.

Now I read in that other post some fellas recommended replacing either the IAC (Idle Air controller - which really seemed appropriate), or the TPS (Throttle Position Sensor - which could also make sense).

So my question to ya'll is this.. What tests can a man with a multimeter do to attempt to nail that down to a specific part?

Also wondering if anyone knows any good places to buy said parts online - I'd try salvage yards, but not expecting too much luck - Despite the fact I live in a huge town (Mesa, Az) there seems to be next to nothing in terms of parts, least not for the other cars I've been looking for, lol.. I'm assuming junking/salvaging would be acceptable for these parts, or should I see if the dealer actually stocks em still?

Thanks in advance,

Rooster

Hey all.. Let me say first off, my problem is quite similar to the following post:
http://www.automotiveforums.com/vbulletin/showthread.php?t=958737

I didn't post/reply to that because it's not the EXACT same and I didn't want to hijack! :)

On my Jeep, after running maybe a minute or 2, once you give it some gas, it'll dive back down below "normal" idle and either stall itself out or give me a good scare that it's going to. After that first minute'ish, it does it every time.

A friend suggested to me to disconnect the battery to reset the ECU (let the Jeep get it's air/fuel mixture reset essentially). That actually SEEMED to work once, but then a few days later the problem resumed. Tried it again, and didn't seem to be as effective.

Now I read in that other post some fellas recommended replacing either the IAC (Idle Air controller - which really seemed appropriate), or the TPS (Throttle Position Sensor - which could also make sense).

So my question to ya'll is this.. What tests can a man with a multimeter do to attempt to nail that down to a specific part?

Also wondering if anyone knows any good places to buy said parts online - I'd try salvage yards, but not expecting too much luck - Despite the fact I live in a huge town (Mesa, Az) there seems to be next to nothing in terms of parts, least not for the other cars I've been looking for, lol.. I'm assuming junking/salvaging would be acceptable for these parts, or should I see if the dealer actually stocks em still?

Thanks in advance,

Rooster


In those first two minutes does eng idle and rev normal? If so, veh is in open loop until 02 sensors warm then pcm takes sensor inf to adj fuel mix. More fuel is delivered in open loop so if you have any vac leaks they will not effect eng as much. several sensors can cause running problems after warm up.are there any codes? Posting any codes will help diagnose.

There a way to pull codes without having the scan tool? I know on Oldsmobiles there's a ignition key on-off trick.. If not, I'll post on this thread when I can get a unit.

Since your veh has newer brain the OBD2 most auto parts stores will scan free.

A crank position sensor will cause this as well.

A crankshaft position sensor will cause stalling.

Would the crankshaft position sensor throw a code?

I took it up to the local AutoZone - At first they told me that the scantool would not throw any codes (or even work) if there was no check engine/service engine soon light on. I insisted I knew some people who knew for a fact otherwise (heh) and asked them to just try.

Long story short, there were no codes relating to vehicle operation (there was an error for my sending unit, which causes my fuel gauge to go haywire from time to time proving that it DID work, the sending of the codes, but dissappointly enough, nothing to pin down this stalling issue. Their recommendation was that perhaps an injector is clogged of maybe even fuel filter. The theory being when it's off, the debris is going back off the item in question into the lines - When it runs for a bit, that debris gets pushed back up there and creates the blockage.

Not sure what I should do. :( Options I can think of are randomly start replacing parts related, or pay some diagnostic $$ and see if the Jeep dealer gets any additional info. Suggestions?

Crankshaft sensor.. So that's going to be in the engine, huh, not mounted on the outside, meaning essentially a rebuild? Or am I horribly wrong on that thought? :)

Hey all.. Let me say first off, my problem is quite similar to the following post:
http://www.automotiveforums.com/vbulletin/showthread.php?t=958737

I didn't post/reply to that because it's not the EXACT same and I didn't want to hijack! :)

On my Jeep, after running maybe a minute or 2, once you give it some gas, it'll dive back down below "normal" idle and either stall itself out or give me a good scare that it's going to. After that first minute'ish, it does it every time.

A friend suggested to me to disconnect the battery to reset the ECU (let the Jeep get it's air/fuel mixture reset essentially). That actually SEEMED to work once, but then a few days later the problem resumed. Tried it again, and didn't seem to be as effective.

Now I read in that other post some fellas recommended replacing either the IAC (Idle Air controller - which really seemed appropriate), or the TPS (Throttle Position Sensor - which could also make sense).

So my question to ya'll is this.. What tests can a man with a multimeter do to attempt to nail that down to a specific part?

Also wondering if anyone knows any good places to buy said parts online - I'd try salvage yards, but not expecting too much luck - Despite the fact I live in a huge town (Mesa, Az) there seems to be next to nothing in terms of parts, least not for the other cars I've been looking for, lol.. I'm assuming junking/salvaging would be acceptable for these parts, or should I see if the dealer actually stocks em still?

Thanks in advance,

Rooster

Ok I see you may have erased codes. Otherwise old codes would be there as you proved to parts guy:evillol:. I asked and you have not yet answered ( those first few mins when you first start) does it run good??? You may have vac leak that is not a big deal when veh is in open loop (first min or so of run, old cars would have choke). But usually codes 02 sensors because vac leak causes lean condition.The IAC controls idle mix and can cause stall at idle. A weak fuel supply can cause your problem with no codes.Did you change fuel filter(I would cause can't hurt) and may solve problem. I am trying to think of non expensive things you can change since your codes are gone.LOL

Ok I see you may have erased codes. Otherwise old codes would be there as you proved to parts guy:evillol:. I asked and you have not yet answered ( those first few mins when you first start) does it run good??? You may have vac leak that is not a big deal when veh is in open loop (first min or so of run, old cars would have choke). But usually codes 02 sensors because vac leak causes lean condition.The IAC controls idle mix and can cause stall at idle. A weak fuel supply can cause your problem with no codes.Did you change fuel filter(I would cause can't hurt) and may solve problem. I am trying to think of non expensive things you can change since your codes are gone.LOL
Nah, codes shouldn't have been erased.. Or rather, they probably were, but there were plenty of opportunities for new ones to surface, as it continued doing this several times from when the battery was disconnected to when it went to Autozone. I didn't answer your last post because I mentioned (no offense) that the car ran run for the first few minutes. Reference the 2nd paragraph:

On my Jeep, after running maybe a minute or 2, once you give it some gas, it'll dive back down below "normal" idle and either stall itself out or give me a good scare that it's going to. After that first minute'ish, it does it every time..
Guess ya missed it - But in any case, that's exactly what I was saying. Jeep runs fine in that first 1-2 minutes. Well enough in fact, that my driving habits and patterns can predict where I'll get to before it'll start acting up on me! :(

Will head up the next couple days and pick up a fuel filter - I haven't replaced it (did try the PCV valve though on an whim) yet. Doesn't seem likly to me (after all, slammin on the gas should get it clogged right away, no need for a 1-2 minute wait), but in any case, there's no reason not to, not like it'll make anything worse, lol :)

Thanks,

Roost

With no codes I would say fuel problem cause that usually doesn't throw codes. I just have a problem with veh running good for first few mins. In first few mins veh is running open loop, so 02s are not being used etc. I have seen bad pcm cause such problems. I would change that fuel filter, and if no improvement check fuel pressure at rail. You could also hook vac gauge to see if you have vac leak,or spray starter fluild at intake or were vac leak could exist. If there is a leak rpm will increase when sprayed. Check all vac lines as well. Good luck