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Hot 4.0 missing at startup.

T

Terrific

NAXJA Forum User
Location
Brooksville, FL
Hello folks.

I've a 97 xj with the 4.0.

When I run the Jeep for a while (20 minutes or so), get it good and hot, then shut it off, and finally restart it, it misses badly. It misses as if a spark plug has been pulled. Sometimes, when this happens, the oil pressure guage stays at zero and the check guages indicator comes on. There is no knocking at all, only sputtering. Usually a little throttle will clear it up and then it will run normally. Sometimes it will continue running poorly for a little while, though not as badly.

At cold startup everything is perfect. This problem only occurs when the engine has been run for a while.

It has only 73K miles on it.

Does this make sense to anyone?
 
Have you seen a check engine light at any time? If so, definitely pull codes for clues. There may be something electrical going on as you have the oil pressure / check gauges thing going on at the same time as you have the missing; I don't think the gauges would flake out if it was strictly a heat soak issue.
 
birchlakeXJ said:
Have you seen a check engine light at any time? If so, definitely pull codes for clues. There may be something electrical going on as you have the oil pressure / check gauges thing going on at the same time as you have the missing; I don't think the gauges would flake out if it was strictly a heat soak issue.
Click to expand...

Check engine will come on, but go away in a short time. It's never on long enough to take it to get it checked. Can they still pull the codes after the light has gone off?
 
I have a 01 that does the same thing, but have never encountered the oil pressure issue. the code i throw is a miss fire on #3. mine did it so bad that i had to let it rest for about 30 min. that was after i was on the trail for about 3.5 hrs and stopped to take a leak. I have had the jeep for a year and a half now and it just started last summer, and has even continued in to these winter months. on two different occasions it was so bad that it cracked the porcelain on my #3 plug. i was thinking i would put in a 190 degree thermostat and a second fan that was weird directly to the battery with a thermostat. just a couple of ideas. I hope to find the fix here. I didn't get much help on other forums. thanks in advance, Jeff
 
peleejosh said:
Search "heat soak". There is a tsb out on this. Don't throttle it until it clears up. Wrap the number 3 injector with heat shield.
Click to expand...
That TSB is only for 00-01 XJs.

bowhunter1227 said:
I have a 01 that does the same thing, but have never encountered the oil pressure issue. the code i throw is a miss fire on #3. mine did it so bad that i had to let it rest for about 30 min. that was after i was on the trail for about 3.5 hrs and stopped to take a leak.
Click to expand...

http://www.wjjeeps.com/tsb/tsb_wj_1803103.pdf
http://www.wjjeeps.com/tsb/tsb_wj_1801001.pdf

One of those TSBs, or both will most likely fix your problem.
 
Terrific said:
Check engine will come on, but go away in a short time. It's never on long enough to take it to get it checked. Can they still pull the codes after the light has gone off?
Click to expand...

Yes, the check engine light does not have to stay on to store a fault code.

Don't ASSUME anything. Pull your codes immediately and post here if you need help interpreting them. Don't want to be chasing your tail when a valuable clue exists on your computer just waiting to help you.....
 
I used the insulator sleeves on 3 and 4 injectors. I had to do some rigging to get them to fit since they weren't designed for the older injectors. It seems to have cured the problem.

I think the oil pressure problem is unrelated and either in the guage or the switch.
 
My "floor it" method fixes this problem. When the Jeep is acting up, floor it for a split second and it fixes the issue.

Now if you are anal about having a perfectly running engine with no quirks the first thing I would do is check the TPS.
 
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