1984 carrera engine stalls

[tafar]

hello everyone!

i'm new to this forum and am hoping someone might give me advise on how to troubleshoot an engine stalling problem. Following are the symptoms: I drive the car for about an hour at highway speed, stop to get gas, drive off along a stretch of road leading to the highway that begs the car to open it up at high rpm's in 1st and 2nd gear (about 5000 to 5500 rpm). Suddenly the engine feels like it's choking, it sputters and putts along until I pull over. This weekend it did it twice. The first time I turned the engine off and after 10 minutes restarted it and drove for another 2 hours in moderate rpm's (maximum 3000), at highway speeds in 5th gear, without further incident. Today it stalled again in 4th gear at highway speed about 4000 rpm. This time it didn't restart. I had it towed home. It did this about a month ago and I replaced the fuel filter and the cap and rotor. The car ran fine until this weekend. Last year I had the 3.2 engine completely rebuilt by Fischer motors.

Any ideas for troubleshooting? Can it be a fuel injector problem? Oxygen sensor? etc.?

Thanks in advance for any advice.


one other bit of information: the engine will intermittently rev to 3000 rpm and back several times over on it's own as if i'm pressing on the accelerator. this happens after i've pulled off the road and have the engine running and on idle.

[john walker's workshop]

be sure the head temperature sensor is updated to the later 2 wire version. pull off the white plug above #3 cylinder and see if the part still attached to the bracket has two terminals inside. the old ones did as you describe. the other usual culprit is the DME relay under the driver seat next to the computer. it has a date code, so be sure it's not too old, and maybe just replace it for general principles because it's cheap and could be an issue.

[DonMo]

Mine did the same and after the easter egg hunt replacing parts it turned out to be a Motronic transistor on the board failing due to the high heat over time.

Fixing it cheap, finding it a B`tch.

[JTL]

The flywheel sensors got me pretty much just as you describe. These things always happen at the worst possible time. like my wife's birthday in this case.

There was no spark so I started checking the permissive dme inputs referencing a Bentley manual. One of the reference sensors didn't check out. Those are a bit of a pain to get to with engine in the car. They are definitely doable though. 90 bucks and a couple of hours later the car has been running 100% ever since.

jt
-84 targa

[eddiehotrod]

I'm with John Walker - head temp sensor.

[JeremyD]

#1 CHT #2 DME Relay #3 Flywheel reference sensor.

if your CHT is cooked - pretty good chance that your reference sensors have all the insulation baked off them too (unless they have been replaced recently)

[tafar]

Thanks everyone, for all of the great advise. This afternoon, with the help of a very generous friend, we changed the cylinder head sensor. It wasn't the easiest project, but somehow we managed. I test drove the car this afternoon, driving it for about 7 miles at high rpm's in low gears and everything works fine. (I replaced the dme relay yesterday as a first troubleshooting step, but the problem persisted). You guys are the best!