Rough starting 99 XJ

Blaze

The Jeeper Reaper
Joined
Aug 9, 2005
Location
Wake Forest, NC
Feels weird asking a question about this, but I no longer have $100k in Jeep parts in a warehouse to throw parts at this thing to try. Now that I actually have to pay for stuff, gonna try and do it once.

99 XJ, 155k miles, auto, 4wd 4.0L.

Majority of the time it starts right up, runs good, drives fine. Then occasionally, like this morning, it starts hard and won't stay running. As soon as you let off the gas it'll stall. If you feather the throttle to keep it running and rev it a few times, let it sit at 2k for a bit, etc, it'll sit down and idle fine and be perfect. It did it in the winter, does it in the summer. Now that my son has his permit we are driving it a lot since it is his Jeep. I'd like to get this taken care of in case my wife is ever out with him and it does it. I taught him how to do it this morning when it did it, but he wasn't great at it. He doesn't have the vast experience driving giant turd piles that I do. :lol:

I'm thinking IAC, but just a shot in the dark in my previous experience at the shop.
 
Any CEL? or codes? I'd check fuel pressure at the rail. IAC can be cleaned and is easy to do to eliminate that.
 
surely check the fuel pressure at the rail, should be 49 psi, also after you shut it off watch to see if it holds pressure. There is a check valve at the pump.

Does it stumble when you turn on the A/C? if so, definitely the IAC.

I've seen the P1391 manufactures code come and not come from the a funky CPS or a coil issue. A weak connection at the alternator will make it screwy too. The 2 pin connector is the exciter from the ECU where it demands current. check and clean it.
 
Oh yea our 98 died one day. Would not start for shit. Had fuel pressure and no spark iirc. We tested CPS and every thing in the ignition. Ended up being dirty grounds. The 97 up will act weird with out proper grounds.
 
Second on check/test battery & alternator and wiring. Sound like what my 98 did last time I changed the battery.
 
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