Hello all, I have a 1996 XJ. its got a lot of miles on it but still strong. I have had an issue with it running really rough after I shut it off for a few minutes and try restarting it. If it sits turned off for more than 30 minutes it runs fine, but if its less then it chugs and spits, if I put the pedal to the floor it acts as if it cleans itself out then runs fine.....I have cleaned the IAC, replaced plugs, wires and cap....any help is greatly appreciated. Oh and it doesn't happen every time. Thanks in advance

 

Could be a MAP sensor issue.

Or, you have one or more injectors leaking down rapidly with the engine off.

 

Injector heatsoak. It's known issue that Jeep addressed with a heat shield. What happens is when the block gets nice and warm and then you shut it off, injector #3 gets heatsoaked and all the fuel inside vaporizes. This makes it run rough until the injector returns to normal temperature. The reason it recovers quicker with your foot down is because you're sending more fuel through the injector, which cools it down faster. You can get the heat shields from a dealer for pretty cheap, so I wouldn't even bother with a parts store since they probably wouldn't have it in stock.

 

That issue was only common on 2000-2001 with California emissions and the dual cats.

 

Missed the year, my bad. Any misfire codes or anything like that?

 

I'm having a very similar problem with my '98 4.0 that just started a couple of weeks ago, so I'll watch this thread rather than start another. Long story short, it only seems to happen 30 seconds to a minute after a restart where it's been sitting for 10+ minutes. No codes, and it only does it at idle or part throttle, it's fine at WOT. It persists for about 20 seconds or so. Not to hijack the OP's thread, but just adding some additional data points.

For the OP, do you get popping from the intake if you give it 1/2 to 3/4 throttle under load while it's acting up? And it's fine at WOT, but goes back to acting up if you back of a bit, right?

 

Yours sounds like TPS.

 

Sorry for just getting back.
No misfire codes. Only code I have is catalyst efficiency....thanks

 

Alright, sorry for way late response. Been doing some tinkering...but still not fixed. I have replaced TPS, Catalytic Converter, Fuel filter, and some of the fuel hose. I also pulled out the IAC and Map Sensor, cleaned them and replaced....even thought maybe getting some vapor lock so, did the old clothes pin trick, still nothing. I am at an end trying to diagnose this old thing....I will say that the issue is happening in a time frame now, more than before. 10 to 12 minutes. When I drive it to the operating temp 220....and let it sit for 10 to 12 minutes (Before 10 minutes no problem, after 12 minutes no problem) and try to start it acts up....but only while in gear....if in neutral or park its not as bad....and once I put it in gear it starts, if I give it gas slowly, then it cleans its self out, smells very strong like gas....

sorry for the novel.

any advice helps.

Thanks,
Rick