High Idle On Startup

[big66440]

My stock 89 4.0 Comanche started idling high when I first start it (does it when cold and at operating temp) I cleaned the throttle body and IAC valve but still no luck, any one have this problem before?

[Guest Sbpunk]

My stock 89 4.0 Comanche started idling high when I first start it (does it when cold and at operating temp) I cleaned the throttle body and IAC valve but still no luck, any one have this problem before?

 

Sorry I don't have a Comanche (i'm buying one tomorrow) but I saw this post and had an answer. TPS or Vac leak. Take some starter fluid and start spraying the vacuum hoses see if the idle jumps. Hit up the intake / exhaust manifold. When you cleaned the TB you might have burnt out your TPS since if they think they're going to get wet they fry. Google how to test it. If it comes up bad they're not expensive to replace. I suggest getting one from a MOPAR shop or the dealership. 

[ftpiercecracker1]

Look for the TPS adjustment. It gives a way to test it.

 

http://comancheclub.com/topic/36382-cruisers-renix-tips/

[big66440]

I checked for vacuum leaks already and didn't find any, I replaced the TPS not too long ago but ill admit I used "standard" after market parts.

[Guest Sbpunk]

I fried 1 on my XJ and replaced it twice with 2 NAPA china parts... both failed. Ordered my third from WeRMopar and fixed my issues. So I'm going to dive into renix here soon but I don't know much about them. The HO TPS go out pretty easy specially if you don't pull it before cleaning the TB

[cruiser54]

I checked for vacuum leaks already and didn't find any, I replaced the TPS not too long ago but ill admit I used "standard" after market parts.

How did you adjust the new TPS?

 

Have you ever done a sensor ground test or a complete ground refreshing?

 

All of these procedures are covered in the link in my signature.

[big66440]

I've tested sensors to the best of my cheapo craftsman DMM's ability and have cleaned the ground by the dipstick and the one to the firewall, I really want to start replacing sensors with as many factory parts as I can but every time I call a dealer the guy on the other line always sounds like its a chore to look up parts for my 89, are there any sites were I can look up factory stuff?

[onlyinajeep726]

Orrrrrrrr....

 

http://www.jpmagazine.com/techarticles/154_1005_jeep_cherokee_xj_problems_and_fixes/viewall.html

 

Scroll down to the part titled, "Run, Run, Rudolph"...

 

Was my problem on my '88 XJ until I tightened the bolts.

 

Run, Run, Rudolph
Maybe it is age, maybe it is mileage, but we've seen a lot of Renix-era ('87-'90) Cherokees where the bolts holding the intake and exhaust manifold to the six-cylinder engine work themselves loose and cause the engine to race around 2,000 rpm.

Prevention: Tighten the bolts, dummy!

 

Cure: Tighten the bolts, dummy!
Seriously though, if your Jeep isn't doing this yet, just check the bolts. If it is idling erratically, grab your 9/16-inch wrench, get the Jeep to operating temperature and tighten the bolts while the Jeep is hot. Be wary of over tightening, though-they like to snap. If you let the leak go for too long you might need to just bite the bullet and put in a new gasket, but often tightening is all that is needed.

[big66440]

Oh and I adjusted the tps with a snap on mt2500 scanner to .83 volts

[cruiser54]

Oh and I adjusted the tps with a snap on mt2500 scanner to .83 volts

What was your input voltage?

 

Did you ever do a sensor ground test as described in my Renix Tips?

[ComancheKid45]

I always thought the TPS voltage spec was closer to .39-.45 volts :hmm:

 

.83 sounds really high... :dunno:

[cruiser54]

It's not a spec. It's 17% of your input voltage. Input voltage is about 5 volts. 17% of 5 =.85.

Usually about 4.8 or so volts.

 

That's on the ENGINE side of the TPS. The TRANS side of the TPS is 83% of the input voltage. The Engine side and Trans side of the TPS on a REnix work opposite of each other.

[big66440]

Ok TPS adjustment did the idle trick, thank u guys.

[cruiser54]

Ok TPS adjustment did the idle trick, thank u guys.

So the MT2500 adjustment worked? Or did you end up doing it with a meter?

[big66440]

It was a breeze with the mt2500

[cruiser54]

It is with my DRB also.

[Jomanche]

We had the high idle for sometime. Cleaned and switched out the IAC, still high but not as bad so we just kept running it. Then one day while we had the hood up giving her a look see while it was running I locked right onto the vaccum leak with my ears and eyes just as an eagle looks onto its prey. One of the caps had fallen off, stuck my finger on it to cover it and she ran like a dream. My kid that though I was a God (he drives our beloved comanche)... I just felt like there,,,see told ya kid. And voila you too will have the same luck. I hope!