Technical issues with the ‘84

[Koizumi]

Hi all, I have a very lovely turbo body ‘84 that I’ve been daily driving for more than a decade. I’ve rebuilt the engine twice since taking ownership - and rebuilt or replaced/upgraded whatever else I got my hands onto).

6+ months ago I did yet another usual tuneup of sorts, valve adjust, new sparks, fuel filter, oil, etc. Car runs beautifully albeit the idle is a little low perhaps. Car has Steve Wong’s chip in it for the last decade.

Suddenly the engine shuts off at red lights randomly. Electric is still on, just the engine just stops. And cold starts with cooler weather the car will start, idle and die. After 20 secs revving, idle holds and I can drive off. The next start a short time later, car starts up fine and idle is good. It’s random it appears.

10-15 years ago, I had a similar issue and it was the DME with cold or corrupted solder joints.

Car gets good spark, fuel delivery is good. Intermittent or random start or shutoff can’t be the CHT or Speed Sensor? Or could it be? I replaced them less than 20k ago.

I’m not sure where to start tracing down the issue. A few years ago I did retrack the AFM. I did not mess with the settings at all, just moved it to pristine track traces instead of the worn track.

Any ideas? I know I’m not being specific enough perhaps but I’ve been reading ad nauseum and I have no clue where to commence my troubleshooting.

Can anyone kindly point me in some direction that might help? I’m lost lol

Cheers

[darrin]

you mention cold soldier joints on your DME, the DME relay can/does develop similar problems which can cause random engine shut-downs. Have you swapped your DME relay (best to carry a spare) to confirm the problem persists after replacement?

[Koizumi]

Yes I have swapped DME relays. I keep 2 working units as spares in my glovebox. I’m currently using the solid state version with fuel pump prime for a few years. I’m
Not sure if I’ve heard of anyone having issues with the solid state versions?

[darrin]

Kolzumi -- there have been a few reports of issues with the solid state relays, but if your issue persists after swapping, sounds like you can rule the DME relay out as the cause.

[Koizumi]

Thank you Darrin. Upon your advice, I’ll try out an OEM relay and see if I get the same stalling or awkward idle etc

[romster]

Does it shut off at traffic lights continuously, or does it disappear after the car warms up a bit? I had this issue a while ago and it was solved by cleaning the idle control valve.

[H-viken]

Originally Posted by romster

Does it shut off at traffic lights continuously, or does it disappear after the car warms up a bit? I had this issue a while ago and it was solved by cleaning the idle control valve.

This would be my guess as well should the DME not be the cause. I had similar problems on my 84 and a good cleaning of the ICV helped

[911obgyn]

If your idle is low, you may have air leak check vacuum hoses and breather stuff rubber doesnt last forever. Once all air leaks are solved you may have to set base idle after cleaning ICV.

[FA-18C]

A couple of other items to check - fuel filter obviously, but my fuel tank strainer was gunked up. At a stop light, even when warm, sometimes the idle would drop down, and the car would stall. Some cranking and it started. This also coincided with a hard start, which through me off. In the end, it was a combo event...filter was pretty bad, as was strainer. Changes both and idle solidified right at 880. Still occasional hard start, like fuel starved - replaced fuel check valve. This helped, but ended up replacing my fuel pressure valve, and shortly after the fuel damper. Now everything is rock steady. Other than the fuel filter, evertying was 34+ years old...all adding to the pain.

[Koizumi]

I’ve ruled out the DME. I tried 2 different ones and car exhibits the same random stalling issue. Cold start it stalls quite a bit but I can ride the clutch (arrrgh) and then suddenly it gets stable.

Today I will go thru all of your suggestions and report my findings. This is very frustrating. Cheers

[Koizumi]

After relentless and exhaustive troubleshooting - my stalling issue turned out to be ridiculous!

Lucky I didn’t start throwing new parts at the old dog (I was about to). I checked everything, sensors, vacuum, fuel system, electronic and electrical, etc. The culprit was not obvious: one of the speed or reference sensor (the bottom one) connection plugs was a wee bit loose in its mating. As the car would vibrate while driven, it would back out and disrupt contact intermittently. Of course I checked all the plugs for mating etc but this wasn’t obvious because the metal wire clip that is supposed to hold the plug in tight was minutely out of shape (only visible from behind). It wasn’t until I decided to ohm out the speed and reference sensors did I discover the metal wire was slightly misshaped on the back side of the connector plug.

Quirks make ownership a thrill lol.

Thanks everyone who chimed in, your advice led me to the pot of gold.

[911obgyn]

Almost free fix. Just time. I love those. Every once in awhile I will spray some Deoxit on those connectors and exersize them.

[Koizumi]

Originally Posted by 911obgyn

Almost free fix. Just time. I love those. Every once in awhile I will spray some Deoxit on those connectors and exersize them.

All’s well that ends well. The quote makes so much sense here

Great suggestion about a little spritz of DeOxit D5, I’m going to do this.

Cheers

[Bill Douglas]

Good skills figuring THAT one out.

[BoxsterGT]

THAT is the proverbial "Needle In A Haystack".

Good Skills for sure.

Len