1987 911 Carrera hesitates during accel

[Nextjato]

My 1987 911 Carrera with 165,000 miles on it runs like a top and pulls like a train until the temperature gauge gets to the 8 o'clock position. Then when accelerating through the mid 2000 rpm range it hesitates. It could be described as a surging. If you shut the car down it won't start until it cools down.... about a 4 hour wait.

Does anybody have any ideas, or seen this before, or know what the hell is going on.

Thanks..

James

[steely]

Just a hunch but check out the symptoms here for a bad cylinder head temp sensor.
You could also do a continuity test of the sensor itself and/or jumper (short) the 2 pins on the DME side of the CHT connector in the engine bay to simulate a hot CHT.
Others may chime in.

[GH85Carrera]

Mine did that for a while. It ended up as a DME issue. I replaced the cylinder head temp sensor and that seemed to help. I replaced the chip in the DME and that helped, but ultimately, sending the DME unit itself in the be fixed solved the issue. It was too long ago to remember the details of what the issue was.

Replace the CHT first. You may get lucky.

[Nick Triesch]

My local Porsche mechanic told me that either the CHT sensor either works or it doesn’t.

[steely]

@Glen - do you think it was a cold solder joint issue or something else?
@Nick - agreed.
There's a troubleshooting guide in the Bentley based on symptoms but this one isn't listed - I think because they didn't address the ageing of the CHT and flywheel sensors etc., and I hate to come off like I am throwing parts at the problem but this could be a candidate.

I wonder of the O2 sensor could be involved as well. The change in the response from cold to warm is a clue, and the O2 and the CHT are used by the engine mgmnt system during the cold to hot transition. It's the CHT initially, and then the O2 when the temps are right, but I am still learning.