problems starting this morning...

I hate to post without doing any research, but Im at work and trying to head out on a road trip after work to make it home for the holidays-+. 2000 XJ, 4.0, AW4, NP242, fairly stock with 142k.

Cold this morning, 20's, jeep didnt want to start. Tried cranking a few times nothing happened. Tried again a few more times pressing the pedal maybe a 1/4-1/2 way down. Finally fired up but ran really rough had to hold the throttle for maybe 30 sec then would run on its own still a bit rough, kinda low idle 400ish. Shut it off and tried to fire it back up better than the first time but still had to use the throttle. Proceeded to do this a few more times and by the third or fourth try it would fire on its own. Idle quality was better but not what it should be. I will note that during this start and stop process that it had ran long enough to warm up to oh say 150 degrees. Drove it to work with no problems.

Check engine light is on, but didnt have time to check codes. No parts stores open at 5 am. It has had a weird problem of popping at random a code for the idle circuit, cant remember the code off the top of my head. In trying to troubleshoot that problem I cleaned the TB on the car and replaced the IAC. Checked and cleaned electrical contacts on the EMC and the IAC. I thought the problem went away when I replaced the IAC but it may be back.

At this point Im wondering if its my TPS. I hope to hell it isnt the EMC slowly giving up the ghost. Wouldnt the Cam posistion sensor prevent it from starting all together pedal pressed or not? I have never changed either the crank or cam and have heard those to be problematic. I would imagine the crank would be a no run, but the cam may allow it to run but not start? Ideas suggestions? Thanks in advance.

Best to get fresh codes and start from there. Symptoms with a code are not coincidental.

Post the EXACT code number(s) here for comment.

Gotta use the technology provided to you by your Jeep........

Well I plan on doing that while getting some parts on my way out of town. Again this was 5 in the morning no option then. So I wont be able to post any codes, unless of course it doesnt start at all and prevents me from making my trek. I was looking for ideas so that when I read that code and use some educated guessing I can buy a part or two to cover my ass out on the road.

EMC? Not familiar with that.

Start with your battery and cables. Cold weather stresses the battery. Fully charge, let it sit outside overnight, and then have it load tested cold. Perform a voltage drop test on the cables: http://www.aa1car.com/library/voltage_drop_testing.htm

There is only one time giving throttle to a fuel injected XJ has any benefit. Holding the pedal at WOT while cranking will tell the PCM (if the TPS is working) that it needs to enter "clear flood" mode--the PCM cuts off the injector firing pulse signal.

If your electrical system is crapping out--likely--then the PCM may be having trouble positioning the IAC correctly, it may not be getting 9.0+ volts and that means all of the sensors are screwy and the PCM data GIGO--garbage in, garbage out.

doh! I meant to say PCM, Im at work and mixing terms. Electronic Motor Controller. Thanks for the input Joe.

milehigh said:

..... Tried cranking a few times nothing happened. Tried again a few more times pressing the pedal maybe a 1/4-1/2 way down. Finally fired up but ran really rough had to hold the throttle for maybe 30 sec then would run on its own still a bit rough, kinda low idle 400ish. ...

Click to expand...

Common symptoms of loose battery connections or a failing battery.

Low voltage causes the Engine Computer (ECU) to re-boot and delete the idle settings.