Rough idle

[greenchevy]

I have a 89 wagoneer limited with the renix 4.0. It used to die on me when slowing down or taking off from a dead stop.Also it never has idled good. The tach needle moves up and down. Also I Found out my egr diaphragm was missing. I got a new one and new vacuum harness. This stopped it from dieing but it still idles like crap. Any suggestions?

[4.3LXJ]

When was the last time you changed your O2 sensor? If it has been a long time, you should change it. It will improve the mixture and make it idle better. Also you might try poring some Seafoam in the gas tank. That will clean the injectors. But don't poor it down the intake.

[BrianXJ]

Why do you not want to put it down the intake. I put some thru the brake booster vacuum tube into the intake. Is that a bad idea.

[greenchevy]

Changed O2 sensor last year. I've ran seafoam in it a few months back.

[steph74]

Did you check your IAC and TPS ?
You may want to give a cleaning to the EGR valve too.
I have taken all the vacuum lines off and cleaned them with a weed eater nylon wire and some WD40.... removed a bunch of crap from there.

Actuallt this is the joy of the renix.... it can be anything ;)


I am too interested to know why 4.3LXJ (who is more experienced than most of us) recommend not to use seafoam in the intake? I can understand the not in the oil thing (on old engine it might create some leaks and stuff) but I don;t see why no in the air intake....

[4.3LXJ]

Why do you not want to put it down the intake. I put some thru the brake booster vacuum tube into the intake. Is that a bad idea.

It can be. If you put too much down it, it will take out your O2 sensor. There are a half dozen members of different forums that have had that happen.

[greenchevy]

I've clean the hoses, egr,IAC, and adjusted the tps several times.With same crappy idle.

[jeepxj95]

did you disconnect the battery????

[greenchevy]

Yep tried battery

[steph74]

Did you change the fuel filter too ? maybe seafoam knock out some crude and it is all nasty inside...
is you fuel pump working good ?

I m not sure if it is true but I have heard that the CPS connections can get lose and dirty and create that.


from reading your initial post, it sounds to me like the IAC. I know you said it is good, but did you check the connections on both side (sensor side and ECU side ? you might have something lose or dirty there)....
You may want to check your MAP sensor too

Heck sorry that might not help but one thing is sure, with the renix you are going to have to track everything, every sensor to make sure they are all working good
good luck

[4.3LXJ]

What RPM does it idle at. If you turn the steering wheel back and forth from right to left or put it in gear, what rpms does it idle at and does it take a dip when you do these things?

[greenchevy]

The rpms when i start the jeep is at 800 like it should be then it drops below 800 and then bounces back past 800.

[4.3LXJ]

It should idle at 650 when warm. What does it do after it bounces past 800 a second time?

Also while you are at it, check your timing

[steph74]

I have a stupid question....
How do you go to check the timing ? is it with this funny gun I see at the autopart store ?

[4.3LXJ]

Yup. Fancy strobe light. Fugitive from the 60s

[steph74]

but then when you have checked and established that it is off you can;t adjust it anyway right ?

[4.3LXJ]

It is adjustable by rotating the distributor.

[greenchevy]

Ill check the timing when i get a chance. It drives fine just doesn't idle.

[4.3LXJ]

The reason I asked to check it is that some engines with computers will stumble at idle if the timing is advanced. It keeps trying to correct itself and will have a miss, which the ECM will try to correct for by readjusting the timing and opening up the IAC. It sounds like yours may be doing that. Anyway, it doesn't cost anything to check it.

[uberxj92]

absolutely 4.3lxj! also check the cps if it is dirty or loose. my 90 renix had the idle issues & backfarting thru the airbox ( which sounded so cool with the snorkel). i ended up replacing the cps & all of the seals on the injectors. one of them had a slight leak. like a mini pin hole in the seal.

[greenchevy]

I've replaced the fuel injector o-rings already and the crank. I bough a DRB 2 scanner. SO lets hope I can get to the bottom of this. Thanks for the help everyone