neilcase

HELP! I have an 87 305 TPI/5 speed car. It sat under a redwood tree for the last 10 years. I bought is as a parts car for my 87 convertible but decided save it because the whole original car was intact. I have spent two months reviving this thing from dead. It runs pretty good now except for one thing. I CANT GET THE IDLE SET! I've followed Vaders great instructions to the tee 3 times now and it sets OK for about 3 minutes and then it slowly works its way up to 1500 and settles there. I'm sure the instructions are correct. If I cant get this solved I can't get it smogged and then it goes back to being a chopped up parts car and that would be a damn shame. Somebody help. Here's what I've done.

1. cleaned entire throttle body and intake
2. All new TB gaskets
3. New IAC control valve
4. virtually every sensor on the engine is new as well
5. set the timing to 6 degrees
6. followed the procedure here 3 times (idle stays at 550 with EST and IAC unplugged)
7. Checked as best I could for vac leaks
8. forgot to mention that the minimum idle adjust screw is backed ALL THE WAY OUT AND CANT BE BACKED OUT ANY FURTHER TO CLOSE THE PLATES ANY MORE. So its gotta be an IAC a vac or an ECM issue?
9. I also set the TPS to exactly .54 volts
10. I just sprayed starting fluid all around the TB and plenum to see if there were any vac leaks. Nothing happened and I soaked it pretty good. (I know a lot of you will say that is stupidly dangerous). But that seems to debunk my theory of possible vac leaks. Comments about that? Is that a reliable way to test for vac leaks?

Here's what has NOT been changed

1. Mass air sensor (cant see why the car would run so good otherwise if bad MAF)
2. ECM (I'm beginning to suspect this is the problem)

I'm thinking either the ECM is buggered up or this thing is pulling air from somewhere at idle. But the fact that idle stays at 550 with EST and IAC unplugged leads me to believe it is NOT a vac leak problem? Its either a bad IAC which is unlikely because it's brand new and the old one was the same problem or a ECM program problem. Would there be any other symptoms of an ECM issue I could look for?

Ideas anyone?

RBob

iTrader: (1)

The TPS may be bad, the voltage setting of it is critical on the MAF TPI cars.

I don't believe that the EST/BYPASS should be open when setting the minimum air:

https://www.thirdgen.org/tpimod2

RBob.

Reid Fleming

iTrader: (2)

If you have a laptop, hook it up to the ALDL port with WinALDL running on the laptop. Check the TPS setting on the laptop. Reason I say this is that I had a similar issue where the car would idle at 1500 and run like a dog idling around. Lots of surging and literally standing on the brake to keep it from loping ahead.

Turned out that although my TPS showed .54 volts with a volt meter, the ECM box was reading it as 1.5 volts at idle. New ECM box and it was solved.

Reid Fleming

iTrader: (2)

I only unplug the EST plug for setting base timing. For min air, I leave it plugged in.

neilcase

OK the problem is gone but.... I got impatient and did two changes at once so I don't know which change solved the problem. I swapped the ECM from my 87 convertible into the 87 t-top car and then I went through the IAC and TPS setting procedure WITHOUT unplugging the EST when setting min idle. Runs perfectly now but as I said I don't know which change did the trick. I suspect it was the ECM so in the near future I am going to swap the original back in and see what happens. Stay Tuned. God that was a bad pun.

tillyvick14

Was there ever any update with this? I just did an L-31 swap for the original L98 in a 91 Formula so the engine and IAC are brand new. It is having an idle issue where it bogs down and sometimes dies at idle. Having EST unplugged seems to correct the issue so I'm wondering if I need to replace the ECM to get this problem completely solved. Thanks very much!

Tuned Performance

iTrader: (92)

Sounds unrelated to minimum idle speed adjustments.
You might want to start a new thread. What are your blm number at idle ?