Kowboy 911

Car running excessively rich. Have replaced DME relay, and head temp sensor, still runs too rich to hold an idle. Hammer shows no fault codes.
Sending ECU for testing. I was curious whether subsequent year (964 or 993) ECU's were compatable?

Arjan B.

A dme relay has nothing to do with rich runnin. May be your engine runs in open loop, so that your O2 sensor is not working and adjusting the fuel consumption.

Also a chip tuning could be the cause, are you sure your DME has his original chip.
A other thing that should be checked, the vacuum lines, especially the one on the fuel pressure reguator. This one is located in the middle upper area of your engine, connected to the fuel line gallery. Here is a vacuum line installed and isa important line for fuel pressure.

Less important for fuel consumption in a possible valve adjustment or worn sparks and a dirty air filter.

Good luck.

Adrian

Dear Kowboy,
No 964 and 993 DMEs are not interchangeable.
Please give more details. You do not provide anything about your 964. You do not tell us anything about who you are or your location. These are all very important issues.
Help cannot be given in such general terms for short non specific posts.
Ciao,
Adrian
964C4

Colin 90 C2

Arjan may be onto something. My fuel pressure regulator had to be replaced when I purchased my car.

The symptoms were excessive richness and no idle. It was actually discovered accidentally when the car was on a lift and the technician saw that the cat was red hot.

At the time, the tech said that this was not a common fault. But I guess that with the age of our cars, the diaphagm eventually fails.

Should probably be a maintenace item once the cars reach a certain mileage. Mine had about 130,000 miles on the odo.

Lorenfb

A rich mixture can result from the following:

1. too high of a fuel pressure
2. misadjusted air flow meter
3. bad cylinder head temp sensor
4. bad performance chip
5. bad O2 sensor
6. shorted to ground O2 sensor wire
7. full throttle switch closed all the time

axl911

I thought cat shoudn't be red hot. Maybe it's got clogged?

anthony
92 C2.

Colin 90 C2

Anthony, the cat should not be red hot. That was the tip off that there was a problem.

The failed fuel pressure regulator was just dumping fuel into the engine, making it run really rich.

Colin