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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21599
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 1991 Porsche 944 turbo, which has an intermittent

Resolved Question:

Hi There,
I have a 1991 Porsche 944 turbo, which has an intermittent starting problem.!
When it has been running, ie still very warm, no problem and the car runs perfectly.
However, when left for a while may or may not always start.
If left for say 1 hour may not start, however come back after 2hours may start.
The car has a new battery and the engine turns over, but does not always fire up.
Have replaced the coil, relay and the distributor cap and still a problem.
Would be pleased to hear your advice and comments.
Kind Regards, Terry
Submitted: 12 months ago.
Category: Car
Expert:  Matt replied 12 months ago.

Hello

This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;

Airflow meter

Crank position sensors

O2 sensor

Throttle position sensor

unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

Check the resistance of the spark plug leads ( 13-15Kohm / metre) and replace if any doubt or high resistance - Also replace the spark plugs if any of them fail this checklist:

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

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