1989 2.5L Idle Issue

[aliecks]

Alright, long story short I got a short bed 2.5L Comanche from my grandpa, he treated it well but he hasn’t drove it much the past few to more than few years.(Other than to deer camp and back once a year) So I’ve have it for a few months and I’ve decided to go for a Street Comanche clone type of deal with the help of ORG parts. Before I get too crazy with cosmetics I’ve been chasing a “stumbling idle” and/or high idle issue. I’ve scanned the forms and watched plenty of Nickintimes plus other creators. I have a Snap-on MT2500 and with my “expertise” lol I diagnosed the TPS being bad. I replaced it, set it to 4.64-4.65v at WOT, I replaced the EGR valve gasket and verified my ISA is functioning. Test drove it yesterday about 10-15 minutes and the truck did well. After getting to operating temp it was sitting at about 1000-1100RPMs with A/C off. Today I drove the truck home about 25-30 minutes county roads, again after operating temp at idle I would be sitting at 1000-1100RPMs. My stumbling idle issue is gone I’m assuming the EGRR gasket leak and the faulty TPS was causing that. I think my ISA is out of adjustment from previous mechanics messing with it causing my high idle.

 

MY FINAL QUESTION: 

What is the actual procedure for adjusting the ISA on a 89? In my Chiltons manual it says the 89-90 doesn’t have idle speed adjustments and is controlled via computer…so is that right or do I go the unplugged ISA 3500RPM route? Or am I completely wrong? Anyways thank you for coming to my TED talk.

[eaglescout526]

 

[aliecks]

I’ll try this adjustment procedure, drive it home and report back later today or tomorrow with how it’s acting. Thanks 

[eaglescout526]

No problem! That adjustment procedure is straight from an AMC|Jeep manual. 

[Sarah Walker]

Looking forward to hearing how it behaves after the adjustment. Since the procedure comes straight from the manual, it should at least give you a solid baseline before chasing other possibilities like a vacuum leak or a tired IAC. When you report back, note whether the idle changes hot versus cold, and whether it stumbles under load. That detail usually narrows things down quickly.