• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

No one Knows??? What is it???

X

XjRomper

NAXJA Forum User
Location
So. California
My problem is when I start my truck at anytime regardless of how long it has sat, will run great for about 3min then it seems like it retards the timing and runs super rough. You can hear the intake suckin mad air and the motor will just about die, but doesn't. After 3min of that it corrects it's self and runs like the best jeep ever made. It has done this since the day I bought it, stock, about 4 years ago. i have serviced my ignition system and it did nothing. Getting ready to upgrade ignition system to MSD offroad 6 and wanted to rectify this issue before proceeding. Any advice is greatly appreciated!!!!!!!!
 
oxygen sensor. i ran over a tree with my xj and it ripped the oxygen sensor wires right out and then come to find out the one that is in the down pipe was bad too so after both of those were replaced it ran like a brand new jeep again. that might not be what you need but your diagnoses of the problem sounds a lot like what i had going on. the engine doesnt know how to run because the computer isnt telling it what to do correctly. and if your getting too much air and not enough fuel.....oxygen sensor. check it out. have a diagnostic ran on your engine and see whats goin on.
 
I'm going to be different from the rest, I say the IAC. It may just need a good cleaning as well as the intake. It could also have a dead spot in it right where it needs to be leaning the mixture at just after start up.
 
i had the exact prob, o2 sensors and i had a bad tank leak stalled every now and then, not all the time, and the intake got reallly loud any check engine light? what year is it
 
it's a 99, 4.0. It doesn't throw the check engine light nor does it throw any codes on the ODB-ll. I have checked the t.p.s., vacumm lines,intakes and throtle body have been cleaned with no change , no better no worse. What is the AIC? That's one thing I don't think I have checked. Thanks guys!!!
 
XjRomper said:
What is the AIC?
Click to expand...

AIC, otherwise knows as Alice In Chains, is a grunge band from the ninties.

A very good one at that. :D:D:D

The IAC, or Idle Air Controller, controls the amount of air going into the throttle body. Since mines carburated, and I can't find an FI head for a 2.5L (I know theyre out there somewhere.....) I have no clue where it is, other than its on the throttle body(behind the TPS, as someone else said). My guess is that its either that spazzing out and going AWOL, or an o2 sensor, since you say its sucking alot of air (maybe moreso than it should) into the engine, thinning out the mixture, Then going back to normal and doing its job. Thats what leads me to belive IAC.
 
Exact thing my MJ was doing, and it was the O2 sensor. Try unplugging it to see if the problem goes away. It'll run (flat) but won't stumble.

I actually ran with it disconnected for about 6 months until two weekends ago. Replaced it and the MAP sensor and it runs great now.

Jeff
 
I am willing to try it all!!! thanks for all the advise!!! Now to put it to the test. Will post more to let you guys know what it is. From what I hear, it's not that common of an issue(as the way I describe it). Give me a day, I'll post back. THANKS!!!
 
well, after 64 bucks and 15 minutes, the truck is now running perfect! Upstream O2sensor seames to be the colperit. I don't understand why it never threw a code on the ODBll. It has been like that for 3 years and never once was there a check engine light. Thanks again for all the help, my local mechanics were trying to tell me that it was an igntion problems,idiots!!!
 
Did you get a chance to read the thread linked in the thread I linked? :looney:

It's something to do with the heater circuit causing strange feedback to the system, but since the heater circuit is "working", it doesn't always throw a code.
 
:chhers:

Thanks for posting the fix, too!

Jeff
 
98XJSport said:
Did you get a chance to read the thread linked in the thread I linked? :looney:
Click to expand...


Yeah I read it. It was the same thing. What I don't get is why aren't my local jeep mechanics hip to this. You think they would have known something about the way those O2 sensors operate. O'well problem fixed with notes taken. Happy Wheelin to all!!!!!
 
You must log in or register to reply here.

Similar threads

techno1154
What is the timing?
Replies
13
Views
2K
cherokeefan_1
cherokeefan_1
J
Cranks, Fires, Dies - 1991 Briarwood Restoration
Replies
17
Views
3K
Jam Master Jay
J
F
Curious MAP sensor failing - symptoms
Replies
0
Views
2K
fenns7
F
W
No Spark
Replies
6
Views
1K
Runnin'OnEmpty
R
M
Oil pressure question
2
Replies
26
Views
3K
Money_Pit_Incoming
M
Back
Top