Glad you found the problem!
The easiest way to adjust the screw back is to hook your scanner back up and let the motor warm completely about 190f + . Then adjust the screw until the iac shows around 30 steps. When that's complete, then adjust the tps close to .5v as possible, your scanner might show close to 0%.

Shut the car off, Then disconnect either the battery or the ecm single weather pack next to the battery for at least 30 seconds to clear the ecm from any learning and codes you had during the problem. It will take about 10-20 miles to get straight again.

If the hunting idle continues, look into adding a ground strap from motor to chassis and one from motor to battery.

[This message has been edited by f85gtron (edited 04-08-2015).]

Ok sounds good going to do that right now and see what happens.

If you do all that and still have a high idle, we will help find your vacuum leak.

Ok It's cold outside brrrr. I brought home my show car so its in my shop and not this fiero!

I hooked up the scanner, I got the car 190+ temp, I read my readings for the IAC and its reading 000 so I changed it out and the new one reads 000 If I rev the engine, it will fluctuate from 27 and back down to 000 idle is around 1050-1200.

Engine loops and jumps from rich to lean condition on the scanner.

I turned that bloody screw in and out and god knows where its set at now, I just turned it until the car stopped looping at idle. Now idling at 1250 with IAC at 000

To make sure we are talking about the same screw, its the screw that adjusts the throttle arm that I'm turning. I know from factory they had a cap on them so guys like me couldn't mess with it but this one had the cap missing so I couldn't resist the invitation to play with it to adjust the idle.

Tps volts are .87 at 1250 rpm.

Ideas?

[This message has been edited by medicman (edited 04-08-2015).]

Anti tamper screw on throttle body

Ok that's a good read but I do have the scanner and it seems easier to read values and be percise with it. I want to know why I'm reading 000 when apparently I should be at 30. No matter how much in or out I turn the screw the scanner reads 000.

It only fluctuates when it's doing its erratic idle. I can understand the ecm is trying to take charge of the idle and that's why it's doing that. It makes the car run rich and lean on the scanner trying to adjust the idle.

Suggestions?

I will try the other way tomorrow if all else fails.

To set the idle after a ECM reset you have to drive the car over 24 MPH, then come to a stop, turn the car off and back on again, that should reset the IAC value.

Due to my lack of patience with the scanner giving me 000 and not knowing why, I went out and followed the directions on the link provided to a "T" took the car for a ride, did all the different things that were suggested and it was idling fine every time I pulled over to shut the car off and restart it the car was around 950 rpm in drive and 1000 in park.

After a decent ride, I pulled back into the driveway and when I put it back into park, it started with a erratic idle fluctuating from 0700-1300 rpm. If i touched the gas pedal or shut the car off and restarted it, the car would idle fine again, this would only last for about 10 sec and then it would start looping again.

Bugger, thought I had it solved. Car seems to have a bog off line but drives nice. I know with the help everyone has been giving me, we will get this thing solved, don't stop keep giving me your experience and lets get this right.

Thanks,

Elliott

Sounds like your down to figuring out a vacuum leak. With the intake hose off, cover the hole that's in the throttle body with the car running....if it dies, the problem is iac adjustment, if idle stays high, find the sucking noise while the hole is covered up. Could be a broken vacuum line, or more likely the egr tube is cracked for an idle that high. The other culprit could be the idle bypass tube that runs from the throttle body to the intake manifold behind the distributor and egr tube.

Ok sounds good. If it wouldn't of snowed last night, I would be out there this morning. Think I'm going to wait till this afternoon to tackle that job.

Well I managed to get out and take off the intake hose and plug the iac inlet hole. The car died right away when it was stone cold and warmed up. So, I guess that rules out a vacuum leak.

I did notice when the car is cold, and you try to give it gas, it sputters bad, it doesn't like that at all. As the car warms up, it gets better but always has a bog at initial revving up. I held the rpm's at around 1500 when it was warm and the the rpm's want to jump from 1300-1500, it shutters just a little, almost like a miss. Now I did put new plugs and wires in before all this started happening and Ive had the wires and plugs off more times than I can count. I wondering If i cracked the porcelain on a plug when tightening them back in and that's why its sputtering bad when cold due to moisture? I pulled wires off while the car was running one at a time on cylinders 1,3,5 and besides the shock I got from each one! the car hardly changed if any in the miss it has.

suggestions?

quote Originally posted by medicman: I pulled wires off while the car was running one at a time on cylinders 1,3,5 and besides the shock I got from each one! the car hardly changed if any in the miss it has. suggestions?

The ignition gurus warn against this practice. It seems that you can send a high voltage spike back through the system and it can knock the ICM out.

No worries, I won't be doing that again lol. It was a shocking experience!!

installed new plugs and wires again! Wanted to rule out any chance of them being bad after I had removed them so many times.

To itemize whats going on, I'll list it.

1) when it starts cold it revs at 2000rpm's
2) If you rev the engine when cold, it stumbles quiet noticeably
3) As the engine warms up the idle comes down to 1000 rpm's
4) Once the engine is warm, it start to loop idle until you rev the engine or shut it off and restart the engine. ( it will start to loop idle from 1300-1000 after 10 seconds when you rev it or restart it)
5) it bogs from idle when reving. no bogging after that.
6) still has a miss when warm but not as noticeable

I pulled off the air intake and pulled the IAC motor hole and it stalls the car immediately so I guess that rules out a vacuum leak.

I was wondering if the screw on the throttle body was not set correctly would it cause these issues. I followed the instructions from the link provided. I still cannot get my scanner to read 30 steps, it reads from 000 to 010. If the TPS sensor was not correct (even though I have never touched it) would that be a area to look at? my scanner reads .87 volts. Should I adjust it to .5 volts as instructed or is .87 close enough?

Thx.

Hi Medicman. A question about your previous problem; injector bank 1,3,and 5 not working. Which wire was broken near the firewall?

Positive wire going to ecm. Pink wire

If your iac steps are low, you've got a vacuum leak. Could also be egr open (cut a soda can up and block off intake-side passage to check). Also, make sure you didn't just set timing on one cylinder, must be an average between 1 and 4.

It's a new egr and I timed it at 10tdc. I went off number 1 and 4. cylinder one is 12 degrees and number four is 8 degrees. So that equalled 20 then divided by two have me the 10 degrees it requires.

Can u explain why I get a 000 reading and 010 max for a count. According to u it should be around 030. Or am I misreading something.

I can tell its way off. Runs like hell when it's cold. Big misses and stalls. Much better when warm. It has a new iac motor and I put a iac diode tester on the wiring and its flashes green and red in a random order.

Ideally, the ecm likes 20-30 steps at idle. This gives it room to move the air volume up and down enough to catch a diving idle or whatever. If you have no steps, the ecm had instructed the iac to close completely and that means the motor is getting air from another source, i.e. vacuum leak, gasket leaks, yada, yada, yada....
Look for any sucking noises, or spray something around the vacuum lines, like starting fluid, wd40, something to make the motor rev up if you hit a leak. Its easy to install the tb and not get the iac pipe-to-intake manifold seated correctly.

If you shut the motor down, but leave the key on, does the iac go way out to like 100?

I thought through previous discussions if I were to take off the air intake and plug the small hole which feeds the iac motor. If it was to stall out the car immediately then there is no leaks? I've done that test and it stalls immediately.

I won't be able to look at any other tests until I shake this flu. Hopefully soon!

Thank you for all the help.

If your confident that you have no vacuum leaks, then the throttle plate is not adjusted closed, or the iac is whacked out. There's a way to test the iac via ohms, but I'm not familiar with it.