Jeep xj runs rough at operating temp after stopping for 5min

[Skep]

Gday

My 1999 XJ runs great except after stopping for fuel of spending 5min in a drive through then the revs will start to jump a bit and sounds like its missing a bit. When accelerating it will buck and miss for a few mins then go back to normal. I have heat wrapped new headers(old ones were cracked) and wrapped injectors to reduce temps around fuel delivary and has helped a little but still feels like i am getting vapor lock. When i bought the car they had replaced every major sensor and new dizzy but couldnt stop the problem. Cheers

[jaffazoom]

mine does pretty much the same.
If I stop for more than about 5 minutes and restart it misses and runs rough till the temp settles back down to normal. It's some sort of heat soak problem but I don't get any errors except misfire on some occasions. Haven't really looked into it.Too busy trying to get time on my diesel xj conversion which will fix the problem then and no doubt start some new ones lol.

Seeing as yours has all new sensors maybe its the fuel regulator, I also thought of fuel pump but don't see the heat connection?

If you find a solution I might fix mine , I just live with it for now

[rustynuts]

I had a similar problem on my "98 XJ. Not as bad as you describe. Just a very slight mis/hesitation after idling for a while. I replaced the throttle body and all was good. I suspect it was a worn TPS ?

[Redemptioner]

Originally Posted by rustynuts

I had a similar problem on my "98 XJ. Not as bad as you describe. Just a very slight mis/hesitation after idling for a while. I replaced the throttle body and all was good. I suspect it was a worn TPS ?

I would hazard a guess it is the TPS too, suffered similar on a couple of occasions and always ended up being TPS. Unfortunately, many of the new TPS sold (including Mopar) become faulty after a short period of time. I bought 2 in the past from 4x4point.com.au and both were faulty new out of the box, bought 2 Mopar ones and both died in short order and played up as soon as they were hot, Crown one lasted a year and started to play up, not sure of the brand I have now (bought locally in a jam with no branding) and it has worked flawlessly for over a year.

The easiest way to check the TPS is to plug a BT OBD dongle (about $12) and look for the fluctuation in TPS output or it failing altogether. The giveaway is the % moving around at idle, car does not have to be running to check this either.

[Skep]

thanks for the replies fellers. Yeah from what I have read the tps comes up alot.
I also read that it could be the fuel tank not venting properly. I didnt reset the ecu after getting headers welded up to the rest of the exhaust ( drove it down to the exhaust shop wth rear o2 sensor hangin out) so it might need to recalibrate but still had same symptoms after pulling out of the shop..

[Redemptioner]

Originally Posted by Skep

thanks for the replies fellers. Yeah from what I have read the tps comes up alot.
I also read that it could be the fuel tank not venting properly. I didnt reset the ecu after getting headers welded up to the rest of the exhaust ( drove it down to the exhaust shop wth rear o2 sensor hangin out) so it might need to recalibrate but still had same symptoms after pulling out of the shop..

You probably got the answer there, pull the plugs on the ECU overnight see what happens

[LuluBelle]

just disconnect the battery for 5 mins
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