Car dies after 10min

RhodeIslandSC · 08-02-2018, 04:59 AM

1987 3.2 car starts runs great 10 min dies no start 20 min later start runs another short time dies. Replaced DMI . Any thoughts

Lyle O · Lyle O's Garage

Check CHT (cylinder head temperature) sensor. Do a search here for more information on this.

Targalid · 08-02-2018, 06:52 AM

When the car dies and will not start, do diagnosis: Is is spark or fuel? Keep a spare spark plug handy and see if it still has spark. Then, do the fuel check for your car. It has to be one or the other. Since the problem only takes 10 minutes to occur, take an assistant on the drive to help you with the tests.

76FJ55 · 08-02-2018, 09:06 AM

My first guess would be CHT, since it starts cold then dies when it heats up and won't restart until it cools down again. next time it does it try disconnecting the CHT (yellowish connector, top of the three mounted on the left intake plenum) and place a jumper into the harness side to bridge the two connectors. the CHT decreases resistance with increasing temperature, so shorted it interprets the engine as hot.

Alfasrule · Alfasrule's Garage

COIL! Had the same problem with my Milano. Different car? Changed everything!!
Put in an old coil I had smooth as silk.
Good Luck

porsche930dude · porsche930dude's Garage

when this happens with lawnmowers its usually the gas tank not venting it pulls vacume and stops flowing fuel. That or the coil

T77911S · 08-02-2018, 10:10 AM

don't shot gun troubleshoot and waste money.

verify you have no spark as said above.
no spark can be the coil or the CPS.

Nick Triesch · Nick Triesch's Garage

My Porsche mechanic friend told me that the CHT either works or it does not . So probably not the CHT .

Lyle O · Lyle O's Garage

The DME changes the running condition based on whether it is up to temperature or not. Lack of input from the CHT is interpreted by the DME that the engine is cold and a different idle logic is used (a properly functioning CHT sends a hot signal at running temp). Once the temp goes up, a functioning CHT sends this signal the DME. If the CHT is not functioning, the DME will think the engine is cold and continue to run the cold engine maps and idle logic, and the car will run like crap (if at all).

danco_ · 08-03-2018, 11:16 AM

Second for CHT.

Had same issue on 993. Worked fine when cold, but as soon as the engine got to operating temp, it would sputter and die, many times at a stop light coming to idle. Once died, it would take 5-10 second of cranking to start up again, but die after I started driving again.

Changed the CHT and issues were fixed.