'86 2.5 TPS adjustment

[Curt]

I've been searching the forums for how to do this, but all I've found is info on the 4.0. Could someone point me in the right direction, please?

 

I just replaced the idle speed motor which seems to work, but after the engine warms up it idles just a little slow. Any ideas other than the TPS?

[Geonovast]

Define "a little slow". Our Jeep motors seem to idle at a lower RPM than most cars.

[Curt]

Low enough that it shakes, especially if I add if I add just a bit more load, like turning the fan on high or turning on the lights.

[rnobles]

I have/had the same problem. I had a 95% clogged vac. line. cleared that out and things got much better! lol

Last night i disconnected the TPS altogether and couldnt tell any change. :hmm:

My engine still idles really low when stopped at a light or something, and if i were to cut the wheel real sharp it will bog it on down. But it will idle up just fine when i put it in park or neutral.

 

So, if you havent already, check your vac. lines. Maybe that will help a little.

[Curt]

I had a vacuum leak a while back so I replaced hoses and eliminated the rubber block coming off the TB. I don't think my problem is vacuum related, but thanks for the suggestion.

 

I found a link to a manual that gave instructions on R&Ring the TPS and I thought it would help me, but it said after installing the TPS to take it to a dealer for adjustment. Bah!

 

I've tried screwing the adjustment screw out on the ISA a bit and that helped briefly, but I think the ECM just compensated by by pulling the ISA in farther. Double bah!

 

It's warming up and I need to start running the A/C, but I need another foot so I can use clutch, brake, and throttle when I pull up to a stop sign.

[Geonovast]

I got in the habit of using one foot on both brake and gas when I'd come to a stop. Both my first XJs had dying problems when you'd throw in the clutch. (bad IACs, I believe. They were both gone before I found CC)

 

The 4.0 Renix throttle bodies also have an adjustment screw that you can leave the butterfly cracked if you want a higher idle. Not sure about the 2.5 ones.

[rnobles]

The 4.0 Renix throttle bodies also have an adjustment screw that you can leave the butterfly cracked if you want a higher idle. Not sure about the 2.5 ones.

quote]

 

They do have it, but you can't really adjust it while the motor is running. And if your problem is like mine, i don't think it will adjust out far enough.

 

As far as adjusting the TPS though. You could adjust it from one extreme to the other and see which one gets you close, and go from there, I'm not sure if the multimeter readings are the same as the 4.0. so you would have to kinda feel it out. just try tilting it one way or the other and see what you get... :dunno:

 

EGR valve in bad shape? I'm going to try that on mine this weekend, well I'm actually going to block it off completely (no regs. where i live). from what i understand, if the valve is stuck open it will equate to a vac. leak.

 

CAT clogged up?

 

These are the next things I'm planning to look at anyway.

 

Good luck. Maybe we both will have some luck this weekend!! lol

[Curt]

I've messed with the TPS adjustment and it didn't seem to make much difference. I was hoping to set it correctly before trying something else.

 

What gets me is it idles just fine when the engine is cold, but after it warms up it stumbles. I've ohmed out the temp sensors, and although I don't know what they should read, the value does change from cold to hot.

 

The EGR valve has been disconnected for a long time. Spraying it with carb cleaner while running doesn't indicate a vacuum leak.

 

The CAT has been hollow for a long time. I have no idea what happened to the stuff inside it. ;)

 

Hey, my MJ is the same color as yours, what are the odds? Mine is taller, though. :D

[Geonovast]

Could very well be your O2 sensor. The Renix systems don't listen to various sensor inputs until it warms up. It goes off of presets. Once it's warmed up, and it's listening to a bad sensor, that could cause your bad idle.

[Curt]

Ok, is there a way to test the O2 sensor? Will the engine run if the O2 sensor is unplugged?

[Curt]

Bueller?..... Bueller?? :(