Calgary Jeep Association

4x4 Related Groups => Tech Talk => Topic started by: 99xj on December 16, 2012, 12:28:53 PM

Title: xj 4.0l revs high and low.
Post by: 99xj on December 16, 2012, 12:28:53 PM

Hello this is my first post in the forum. Yesterday noticed my jeep when idle for couple mins would try to stall then rev high. Also sometime while driving feel cutting out!!!

Since then today I have flushed fuel system and cleaned TB. Also replaced TPS sensor. But is still acting up.

Motor is stock besides gforce chip and throttle spacer. Please any ideas or help greatly appreciated

Title: Re: xj 4.0l revs high and low.
Post by: yellowjeep101 on December 16, 2012, 01:04:46 PM

Check engine light? If so, check the code. Check the code anyways, maybe your check engine light is burnt out. I'm thinking you have a o2 sensor that is done.

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 16, 2012, 01:20:25 PM

the check egine is not on at this time and since started idle problem. But has came on and off over last couple of weeks

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 16, 2012, 02:09:48 PM

after reading some forum post i see could be IAC valve so just got one from napa I'll see if this is the fix

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 16, 2012, 03:15:19 PM

replace the Idle control valve. didnt fix it. now after jeep gets to running temp at idle it will act up rough idle. If I turn it off and back takes about 10 minutes of idling for it to do it again...

Title: Re: xj 4.0l revs high and low.
Post by: apeman on December 16, 2012, 03:20:08 PM

Most likely the upstream 02 sensor.

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 16, 2012, 03:35:09 PM

Ok thanks I see yourself and yellow jeep think is the samething.  I am going to give that a try thanks to you both

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 17, 2012, 03:26:55 PM

Today I checked codes, Nothing, swapped o2 sensor main stream. But still when get to 100 temp will start to idle rough up and down. once turned off will run fine again for 10 mins or so.

Title: Re: xj 4.0l revs high and low.
Post by: WagoneerXJ on December 17, 2012, 03:48:38 PM

G force chip? That the resistor thing from ebay?

Title: Re: xj 4.0l revs high and low.
Post by: WhiteOut on December 17, 2012, 03:49:50 PM

Best place to start is to remove the chip.

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 17, 2012, 04:41:46 PM

I removed it but  still does same either way. Totally stumped now.

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 17, 2012, 04:43:00 PM

the Gforce chip Im not too sure it was installed when I purchased jeep.

Title: Re: xj 4.0l revs high and low.
Post by: apeman on December 17, 2012, 04:58:15 PM

Coolant temp sensor malfunction.

Title: Re: xj 4.0l revs high and low.
Post by: 99xj on December 17, 2012, 05:05:45 PM

where abouts could I located that under hood. I will give that a try thanks.

Title: Re: xj 4.0l revs high and low.
Post by: yellowjeep101 on December 17, 2012, 08:33:24 PM

I'm still thinking its your o2. I had similar issues and all it was was that sensor

Title: Re: xj 4.0l revs high and low.
Post by: WagoneerXJ on December 19, 2012, 01:44:18 PM

Quote from: 99xj on December 17, 2012, 05:05:45 PM

where abouts could I located that under hood. I will give that a try thanks.

I believe thats the one on the front of the cylinder head, right by the thermostat housing. Easy to find.