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Old 04-24-2017, 08:59 PM   #1
below the surface
Join Date: Aug 2013
Location: New Orleans
Default From No Start to Cold Stalling (1986, 240, NA)

I may have declared complete victory too soon in solving my no start problem.

After installing the new ICU, my car starts fine, but it now stalls frequently until it reaches operating temperature. It seems to happen most frequently when slowing down, either by braking or downshifting. Once the car reaches operating temperature, it generally runs fine without stalling.

Does the new ICU need to "learn" the car?

I have at least one undiscovered vacuum leak (hissing in the dash when shutting off) so that may be part of the problem. But it seems that rather than running the RPM down zero and stalling, the engine is somehow just turning itself off. When driving during warmup, it will just shut off as I'm slowing down. By revving, I can keep it on; or I can downshift to 2nd for a rolling start.

I know that a faulty brake booster can cause this problem, however, my brake booster is nearly brand new (installed earlier this year). I suppose it could be a near immediate failure of the new part.

Perhaps I have some other vacuum leak? I know the climate valve may be the culprit. But I am suspecting as more likely some other electrical cause, due to my previous ICU failure.

Idle is relatively steady around 700rpm after warmup, it's not jumping all over the place. I previously had a much worse vacuum leak (totally rotted flame trap) which caused crazy idling but only occasional stalls.
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Old 04-24-2017, 09:51 PM   #2
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Join Date: Nov 2015
Location: Athens, GA

Mine would make a 'whoosh' sound whenever I would turn the car off. On the driver's side, remove the plastic panel which connects to the center console. Do the same for the passenger's side. There is about a 1'' long x 1/2'' diameter black hose connected to an oval shaped white plastic bottle-like contraption on each side. There is also a small, bent, hollow metal tube going through the black hose which then is connected to a smaller vacuum line on each side.

I took these out, cleaned them with some alcohol, allowed to dry, and carefully put some permatex (blue) around the pieces and reconnected the vacuum line. I also did this to the piece that connects to the intake manifold under the hood. It stopped some of the issues I was having.

Also, I had to lengthen the wires from the hall-effect sensor, as they were tight from the many years of off-gassing and had become hardened in the process.

Another culprit for me was one of the smaller wires coming off of the battery cables. Be sure to check not just on the top for cracks, but specifically underneath. Mine would lose power completely going up a hill because the bare portion of the wire would short out on the metal fender.
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Old 04-25-2017, 09:25 AM   #3
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Join Date: Dec 2016
Location: Fort Lauderdale

I had a similar issue in my 87 that was ultimately vacuum related. I would check the Idle Air Control valve. Sometimes they get gunked up and you can spray some throttle body cleaner through it to clean. If it is working, you will be able to feel it vibrating in your hand.

Any climate control vacuum leaks are unrelated to your running problems.
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Last edited by Kenunot; 04-25-2017 at 05:36 PM..
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Old 04-30-2017, 07:31 PM   #4
below the surface
Join Date: Aug 2013
Location: New Orleans

Cleaned the Idle Air valve. No obvious gunking up; also I had cleaned it within the past couple years. Also checked it with a meter, 20 Ohms from center pin to either side, 40 Ohms across the two outside pins. Idle valve appears to be humming normally during operation.

No change, still stalling.
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Old 05-15-2017, 11:25 AM   #5
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Join Date: Sep 2012

This sounds like a more serious vacuum leak to me all day long.

You can test your brake booster pretty easily doing press and hold type tests.

You can make a pretty easy smoke tester with a paint can, an oily rag (or wood) and a length of vac hose to the intake
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