Hope someone can help me with this.

I drove my '89 IROC 305 TBI with 60k miles on it from Dallas, TX to Hunstville, AL in December . I had been using it as my daily driver for a contract job that keeps getting extended. At Christmas, I decided to bring it home and put it away for the winter. The car ran perfect and I got my usual 24 mpg during the trip. At Easter, I came home to AL for a long weekend and went to start it. The car started a little hard but then refused to idle. I had to hold the revs around 2000 rpm to keep it running. I did manage to get it on the highway, filled the tank, and drove it about 10 miles with no change. At speed it runs great but when I let off the gas it doesn't idle.
Fast forward to this weekend and another trip home. After going through all of the tech articles related no idle on a TBI, I concluded that my problem was with the IAC and purchased a new one. After putting it in, I see absolutely no change. It will still not idle.
It's going to sit for another 2 months until I return home at the conclusion of my contract and I would really like to have a plan B to get it going again. I would really appreciate any suggestions.

 

I'm not sure what it could be, but perhaps it's a misfiring on a cylinder or more? At idle that would be very noticable, but at higher speeds and higher RPM less so. Maybe the timing is off or something like that as well. I don't want to say its the fuel pump, because it doesn't sound like it although a very common problem with this car. Before mine went out it would not idle as well, after leaving it sit idling very poorly for a few minutes it would eventually smooth out and could be driven. Luckily that doesn't sound like you're problem, because unless you plan on doing the work yourself, it can be a pricey repair.

Again, sorry I don't have a really good answer for you. Hopefully it will help somewhat.

 

Thanks for trying but that isn't how its running. There were no issues with how the car ran until I parked it. There is no mis-firing, back firing, or any thing like that. There are no engine codes, nothing has been modified or changed from stock, or anything else messed with. It ran great when it was parked and now it just won't idle. The only thing I've changed is a new IAC which made no difference at all.

 

Any suggestions?

 

Have you taken the air cleaner off while the car is running to see how the injectors are spraying fuel?

 

Check to make sure your fuel pressure in within spec, had this problem before and turned out my fuel pump was on the fritz

 

Thanks. The spray pattern looks even, but again, if I don't keep the revs up the car doesn't run.

 

I would think that the fuel pump would act the opposite and starve it at higher RPM. But I will check it the next time I get back home. Thanks!

 

I had a similar issue... Turns out there were some vac hoses that were leaking/dry rotted. Not sure if thats the whole issue. But that seems like a good place to start. A little sea foam never hurt anything either.

 

I'll look at them as soon as I get home but it doesn't quite act like a vacuum leak. Vacuum leaks always seemed to create a surging type of problem whereas mine will just not idle. It just bothers me that it was running perfect when I parked it.

 

I you do a key on engine off is the IAC doing the visual routine?

 

Thanks but I guess I'm not aware of what the visual routine consists of. Could you explain please?

 

KEY ON ENGINE OFF the IAC extends to full position(200 steps?) and then retracts to a position determined by coolant temp...You can see it by looking down the TB in the IAC passage way

 

Got it. Thanks. It will be awhile before I can try this as I'm working in a different state than where the car is and I've got another month or so to go. This sounds logical so what is the next step if it doesn't extend and retract?

 

If does not function it could be ECU or wiring from ECU or a faulty IAC. My IAC failed in fully closed position