Roc87

My '88 Drivetrain in my '81 elcamino has never idled correctly when it's first started up or when the a/c is turned on. I did the entire drivetrain swap, but did not drive the '88 trans am for more than 2 days and don't think it had this problem.. But, the stock chip was in the ecm when I was driving it home, there was a hypertech chip in the glovebox. Once I got everything swapped over, the stock chip wouldn't allow the elky to start, as I didn't swap over the VATS and all necessary equipment. I tried the hypertech chip and it started right up. But it seems as if there is something wrong with it as it doesn't seem to have a fast idle when first started or with the a/c on. During the past couple of weeks, I have to keep one foot on the gas and one on the brake when slowing down and at a stop to keep it from stalling. I have a very old scanner that does show that the a/c system is requesting the high idle from the ecm, but there isn't any change in idle. Is there any way to verify that the chip is the problem? Don't want to spend $200 on a chip, but don't want to burn my own either as the elky is just a daily driver/occasional trailer puller (4 wheelers). Any help or suggestions would be greatly appreciated.

CRUSHER

Did you try adjusting the TPS sensor, and IAC??....they could be out of spec...the adjustment procedure is in the Technical section on this site. Very easy to do....try that and see if it helps....IAC could be dirty also....clean out the IAC passages in the throttle body first before adjusting anything..A dirty IAC could cause rough and surging idle...

runningagain

http://www.diy-efi.org/gmecm/papers/tunetip.html#idle That is a good place to start, my truck is having trouble too. I may have to look at my chip I had programed to see if something is wrong. Let us know what you find.

Roc87

I have a very old scanner and it shows that the ecm is calling for 650rpm in park/neutral, but the IAC count is ZERO. I tried the procedure to reset the IAC (Turn key on, jump A-B, unplug IAC, start) It wouldn't idle at all until the adjustment screw for the throttle blade is all the way in. Adjusted TPS back to .48 - 4.7, and the IAC counts still show ZERO. Tried turning on the A/C and the scanner shows the ecm is calling for 670rpm.

When I had the parts powdercoated, I couldn't remove the block for the IAC off the throttle body, so how do I go about cleaning it? The IAC has about 10k miles on it, replaced when I did the swap.

shingadaddy

Also remember that if you disconnect your battery for some reason, this can throw the IAC position tracking off. The manual states that you can get it to correct itself by:
1. Engine OFF
2. Applying a slight amont of throttle
3. Start engine and let it run for at least 5 seconds
4. Turn engine OFF while holding the throttle at this position
I believe this force the ECM to try and reduce the idle by closing off the IAC, essentially telling it to go to the closed position. Manual say to then re-start and the IAC position tracking should be in sync with ECM. Disconnecting the battery also causes the ECM to loose is LEARNED parameters and it may run a little *odd* until you drive it initially. (Re-learn a few things.)
"I couldn't remove the block for the IAC off the throttle body". I'm having trouble understanding this. Do you mean you couldn't get the IAC out?
Or did you get it out and not block the port from getting powdercoated?
Sorry. Probably me just being goofy..

Roc87

I was going to get the outside of throttle body powdercoated to match plenum, but the screws holding the block for the IAC were breaking off.

I pulled the chip out today and sent it off for it to be "looked at", they are going to check over fuel/spark tables, tcc lock up point, fan on, etc., told them I wanted the cold idle and ac on idles 100 rpm higher than what the chip currently calls for.

Also pulled off the throttle body and went ahead and broke off 3 of the remaining 5 bolt heads. Got the thing completely apart and broken screws out of throttle body. Took it to a friend that works at an auto shop and he's going to soak it in the parts cleaner for a while and give it a good scrub.

Ordered the TB gasket kit off ebay along with a low temp fan switch and an air foil (Yes I know, an air foil )
Will let you all know how it turns out..

shingadaddy

My scanner shows IAC counts and LEARNED IAC counts. you say yours is showing ZERO? I believe this is fully CLOSED isn't it?

Roc87

160 is fully closed. I think it was was fully closed as I had the min air screw all the way open and the actual idle (when it would idle) was higher than the requested idle.