Carrera shuts down after warm up

[theiceman]

My friends carrera runs great until it warms up . we tooled around the neighbourhod fine and when he took it on the highway it started bucking wildly . We dipped the cluch and it oscilated from 1- 3,000 rpm then died . We could NOt restart it. i stuck a spare plug on the lead and it was cranking over and firing with no start but tonnes of spark . After waiting half an hour it would start and we made it about 5 hundred yards before it acted up again . We left it overnight, went back and got it today and he drove it home. Weird.

Since I was getting spark I am assuming fuel , we removed and inspected the DME realy , even took it apart .. looked like Brand new..

on a side note any idea what the symptom of a bad CHT sensor would be ?

also the car has brand new fuel filter, plugs and rotor. ( changed before the spark test )

Any other input welcome ..

the advice I have so far

[Flat6pac]

I would jump wire the fuel pump forcing the fuel to run and it by passes the relay. Your fuel pump may be defective and you cant hear it run with the starter turning.
Bruce

[DonMo]

It could easily be the brain or Motronic computer. Mine had a transistor fail due to heat and as it heated up it wouldn't run until it cooled. It could also be a bad solder joint, very common to the 3.2's. I ended up having my brain rebuilt. Don't go down the road chasing parts, find a friend with a 84-89 3.2 and swap brains. If that fixes the problem, a $350 rebuild will fix the problem. If not, you can start doing the CHT's, DME relays, etc.

[kidrock]

I'm with Flat6pac on this one. I had a similar issue in the past, sounds like your fuel pump is ready to take a dump.

[kodioneill]

Possible reference sensor intermittent open circuit.

[theiceman]

Hey guys thanks for the info .. I have an update .. was over there tonight as he managed to limp it home . I checked theCHT sensor and it is working as designed , it was warm when i got there so about 800 ohms , i had him start it and when it warmed up I unplugged it and it started to oscilate wildly .. I plugged it back in and it settled down. I measured the resistance and got 168 ohms and I think 170 is spec. I did notice however it was the single wire system and suggested he upgrade. While standing watching it started to hicup and I heard what sounded like a rush of air .. I think the ISV was trying to compensate for soemething. i looked closer and found what I thouht was a surface crack on a 1" piece of rubber connecting a horizontal pipe to the intake behind the blower . i stretched it to see if there was a hole and the whole piece came right off ... well that ain't kosher ..

he is going to take it to his maintanance shop tomorrow and have another piece of rubber crimped on . I will update after that .. although i am optimistic i am still thinking fuel pump or DME , but we will see..

BTW doesn't reference sensor trigger spark ? I had full spark when cranking and it wouldn't run .. i would agree if I had to spark and no injector firing. leads me to a good point though I should check next time it fails to se if i am getting 12 volts at the injectors .. any idea of the duty cycle . would by fluke 87 catch it or am i dragging out my scope ?

[wswilburn]

This was exactly how my car acted with the 1-wire CHT failing. I could clean grounds, etc. and it would work for a while. It may not be his problem now, but you are right to recommend replacing with a 2-wire CHT.

[wente]

My 87 was doing the same thing a few months ago. After replacing the DME relay, the CHT, and the coil, it quit at 60mph on the freeway and I had to have it towed home. Turned out to be cold/cracked solder joints in the ECU below the large darlington transistor mounted on the heat sink. When it warmed up, the crack would open and the car wouldn't start. After cooling about 20min, it'd run again. I reflowed the solder joints, and haven't had a problem since.