Stupid Engine

OK, so about two weeks ago I was driving along and my Jeep just randomly cuts off, and won't start back up.. Well as I was too far away from home or any tools, I had it towed to a shop where they replaced the dist. cap and rotor, as well as the CPS. Well here I am two weeks later driving home from work when all of a sudden my Jeep dies. Well I pull of the road, and I try to start it again, well it starts just fine, but you can tell it is idling roughly, and wants to cut off, but if I hit he gas, it will sort of idle back up and run like it should and then it will drop off as soon as I let go of the gas pedal... I am going to check the CPS in a few and will report back the findings... but I doubt that it would have failed already... unless the crappy shop installed a used one, or didn't replace it in the first place... Was wondering what other ideas people had to check, as I really can't afford to keep throwing random parts at it or take it to a shop again right now!!?? OH yeah and both times absolutely no CEL or any codes to help!! Thanks in advance for your help!!

Couple of things you can try. Check fuel pressure at the rail. Check the IAC to see if its clean and working properly. Unplug the different sensors until you find one that doesn't affect the idle (even the coolant sensor will cause a really rough idle as the computer tries to compensate). Look for sporadic vacuum leaks.

First thing I would do is pull out the spark plugs and check them for color and gap. They shoud ALL be consistent whitish tan and 0.035" gap. Spark plugs tell you a lot about your engine condition. And if other things went bad before, they could be partly fouled out.

I will check all of those thank you for your help... I just went up over 8 hrs after it died and threw some gas in just in case it was out, and it ran fine, so I at least have it at home... but I am not sure if that was the issue or not as I didn't think to start it prior to putting in the gas to see.. The issue with checking sensors to see if they effect the idle is that, once I start it, it will chug for second and then shut off, so I wouldn't have enough time to see if it would work or not... but after this next pay check I will fill up the tank a bit more and drive it or at least l it run in the drive way to see if it might be an issue that only shows up after running for a bit. Is it possible to be an issue that might show up after the engine warms up, and if so what are the options for the problem then??

The only one I could think of was the "up-river" O2 sensor if you will, as I have read that the ECM reads it once the engine is up to operating temp., which would be roughly where it was this morning when it died and started acting up. Any other thought would be helpful.

You mention your foot on the gas will smooth out the idle. How about a TPS (throttle position sensor)? I've been fortunate in never having to fool with one, but I know cleaning a dirty throttle body can help with idle quality, as in the air passage that by-passes the throttle plate, allowing the engine to idle with the plate snapped shut. Just a thought.....

check the wires exiting the CPS-- it's relatively easy to have them mis-routed and allow them to contact the exhaust.

I was thinking the TPS but it runs just fine right now... so I don't know if it is only an issue once it warms up, or what, as I haven't given it a chance to warm up since the issue this morning.. It also may have just been since my fuel guage is messed up that I might have been out of gas, since I put in two gallons and it ran find driving it home from where it broke down this morning... Once I get more than just two gallons in it I will let it run in the drive way a bit to see if it is an issue that only occurs once it starts to heat up...

I will check the wiring and routing of it to make sure that it isn't sitting too close to the exhaust just in case that is why it started ot act up once it got to operating temp.

How is the motor temp? I know this may sound dumb, but I had a buddy who had an old Scout and it would run great until it warmed up then it would run real rough and die. We would mess with it and just could not figure it out. Start it up the next day and it would run fine for a few then start running poorly again. While working on it we realized that it seemed hotter than usual and the radiator was cold. Pulled the thermostat, tossed it in some boiling water and sure enough it didn't open. Replaced the thermostat and had no problems. Turns out it was overheating. It would run fine until it started to overheat but you couldn't tell it was overheating because alot of the tell tale signs were not there, ie. radiator blowing off steam or boiling over, etc. Just a thought.

I will check this out shotgun...as this seems similar to what it is doing... it runs fine until it is up to operating temperature... then it starts running rough for about a sec or so and then dies off... it will start back up but will immediately die... unlike when the CPS went out last week.. it just shut off then would not fire back up at all...

CPS (AKA more correctly CKP) are also known to be heat sensitive. Splash water on it to see if you can restart.