1981 fuel injection - stalls while driving if idle

[jtmachen]

Hi everyone,
I looked through and saw some similar posts, but not exactly the same as what I'm experiencing.

After the engine is up to full temp and I've been driving for 15 to 20 minutes the engine begins to stall when it comes down to idle. When pushing the clutch to shift I must be very quick because if the engine speed slows too close to idle speed it will stall.

I can ALWAYS immediately restart the engine, but have to keep my foot slightly on the gas as I do or it will stall again. As long as I keep some level of pressure on the gas it will continue to run (hard to do when also trying to slow down or brake).

Once the engine has cooled off it will run fine again until I've driven another 15 to 20 minutes and then the issue starts again. Any ideas on what is wrong?

[18Fiatsandcounting]

My first guess is that your idle speed is not set correctly. Many people assume it's the throttle stop screw, but it's more complicated than that. It's actually set using the air bleed screw in the throttle body. In a nutshell:

Make sure the accelerator cable is loose enough at idle so that it's not holding the throttle plate open.
Warm up the engine.
Close the air bleed screw all the way (don't force it, just lightly snugged).
Adjust the throttle stop screw until the engine just barely idles, like 600 rpm or so.
Open the air bleed screw until you get to the desired idle of 850 rpm.

If that doesn't work, another thing to check is the adjustment of the throttle position sensor (TPS), as that gizmo tells the ECU when the throttle plate is at idle, and the injectors behave accordingly.

Another thing that can go wrong is the o-ring around the air bleed screw can be leaking air, but this usually causes a higher than desired idle.

-Bryan

[jtmachen]

Thanks for the help on this. I did make some adjustments and I didn't seem to solve for the issue I was having. I started replacing parts one by one and my first part solved for the issue. It was the ignition control module mounted behind the ignition coil. Replaced that and drove for a good hour and it never stalled. Thanks again for the suggestions!

[Rweiss6]

I’m having similar issue. Which ignition control module did you get , I have ‘81 too. Mine is about 3 years old, was put in by mechanic, similar issues then too he said it was a GM part , car was pretty new to me then , have learned and done a ton since, this forum been huge help.
Any heads up about changing it myself ?
Thank you.

[jtmachen]

I bought mine from vickauto.com. The part is Ignition Control Module, Fiat/Alfa Various - (SKU 21-3601).

It's pretty easy to change, you just need to remove the ignition coil (looks like a hairspray can) bracket on the passenger side of the engine compartment. The control module is right underneath the coil. Just undo the bolts and disconnect the wires, then reverse the process to install the replacement.

[Rweiss6]

Ordered it, thanks for your info. Just noticed your post was many months ago. So it’s clear the ICM was the problem ?
Do you know if they can fail slowly, become erratic , not suddenly die ? I just put new alternator in, thought maybe the new stronger voltage might have affected the ICM.
Just an uneducated guess. Car ran well today , but only short hops. Enjoy your Spider !!!

[jtmachen]

Hi there. I haven't been driving it since June because of the heat here in Phoenix, but it ran fine for the months after I replaced the ICM. I've read on some of these forums that these have a history of failing and that you should always have an extra in the glove box, so I ordered 2 of them just in case.

[Rweiss6]

Installed ICM yesterday very carefully and checked connections , seems tight as much as before.
Car started right up but much lower idle, drove a bit , very sluggish, no power. Wonder if ICM faulty ? I asked Auto Ricambi , always very helpful, they said send back for testing, have had some w issues.
Ordered another one on line, GM type suitable for 81 Fiat. will install asap and update here.
If there is something else to do or check, please let me know

[18Fiatsandcounting]

Please do let us know. For some reason, ICMs seem to be problematic, and I've heard stories of 2 or 3 new ones being tried before a good one was found. I'm not sure what's going on... Perhaps a bad batch made their way into the market?

-Bryan

[jtmachen]

Or maybe try the one from Vick that I posted. I assume they are both selling parts from a different supplier

[Rweiss6]

Got new ICM from auto supply place on Amazon. Installed and everything seems good, took long very fun drive ,really warmed up , I stopped and started bunch of times.
Today I very securely attached wires from coil, now I’m not sure it was as secure as this other day, could be wasn’t fully attached like today ??? Maybe that’s the issue ?? Also I sandpapered contacts today as much as I could , not sure it made any difference but tried that too.
I emailed Auto Ricambi, asking to send it back for their testing, if it’s ok I’ll take it back as a spare , if not a credit towards next order. I’ll pay postage , nbd.

[Coolbreeze]

What other components might cause intermittent ignition failure besides the ignition control module?
I drove my 1980 Fiat Spider 2000 home from a specialty shop in Peoria (~100 miles) through country roads just to have the ignition crap out on me at the edge of Springfield. The engine would die, but would restart after a short cooling period. Usually, it ran poorly after restarting. It would buck, snort, and fart out the exhaust. [Much like me when I get up in the morning!] To me, that sounds like an ignition problem.
I had the distributor replaced last year. I am not sure where the ICM is located, but if it part of the distributor, I should be able to replace the current ICM with what is on the old distributor. Does that make sense?

[Rweiss6]

I think the ICM could be the problem, as I had similiar issues 3 years ago and again recently. Both times ICM
Replacement solved it. A Fiat mechanic put in a GM type ICM 3 years ago , I bought one from Auto Ricambi which didn’t work properly - it may have been my not installing connection tightly enough, although there are bunch instances of faulty ICM. I’ve been very happy w parts from Auto Ricambi, want to say that.
Anyway, it’s not hard to install, it’s behind the coil on the passenger side against the inner fender.
Disconnect battery, unscrew the coil , be aware of all connections, the ICM is held by two screws and two contacts at top and bottom. Wire new one exactly as old one. I sanded all contacts and securely attached second time , I bought one on Amazon , its inexpensive part , about 20 bucks , comes with heat protection gel , apply to back of it before screwing it in.
I found a YouTube on this btw, just remembered, but it’s really not big job.
This Forum has been very helpful many times including this problem. Car runs fine now, love driving it now w confidence

[Coolbreeze]

I received good advice on this forum and from Vick Auto Sports. I plan to replace both the coil and the ICM. That can be done for less than $100. It should take care of the problem and give me piece of mind on trips. I shall clean the contacts also, of course.

Thank you for answering my concern.