Regarding a '97 993, there has not been a recent post on this topic. My check engine light pops on and a Cylinder Misfire is diagnosed as the problem. I have replaced plugs, distributor cap and rotors, spark plug wires with no success in keeping the light off. The mechanics (one independent and 2 authorized) have no solution. What's the latest thinking on this?

 

Where do you live depends on the solution.

In California a CEL is translated to get out Checkbook.

 

It's tough..... I generally believe that the check engine light on the 993 has a lot due to mis fire...... But my light generally shuts off in about 1-2 days

 

Had the same issues with mine and replaced everything you did along with ecu and alternator,battery,isv valve,complete secondary air injection clean out. Turned out to be 2 fuel injectors were bad and leaking fuel or not giving enough fuel. Now 600 miles and no misfires

 

check the injectors first ,if thats good my bed is on the dual mass flywheel...to check the flywheel.. see and hear how the engine is running when cold. (engine lid open )..when engine becomes warmer see if its starts to stumble and "shake" like its missing... ( its kind hard to discribe ) hope this helps ....otherwise take it to a good porsche tech who works on the'' old' stuff ...

 

My 96 had CEL issue for years and the codes reported were misfires. The car felt like it was running fine, and I replaced about everything I could think of without any luck. I had read on this forum that having non-Porsche belts could trigger the problem but didn't believe that could possibly be the cause. About three years ago I finally broke down and replaced all of the belts. The alternator belt was an OEM belt made by Continental. I haven't had the CEL go on since.

 

Make sure you have Porsche fan & alternator belts on the car. Also make sure the intake temp sensor is working properly.

Is it the same cylinder all the time, or is it all of them? If the injector is bad, you can move it to another cylinder then see if the mis follows the injector.

If it is the reference sensor on the flywheel, you should get a bunch of random misfires.

 

Flywheel - I had the same misfire problems. New flywheel solved it.

 

Thesed are all fresh ideas, I'm passing along to my mechanic. And I do have a feeling that this quickly get the checkbook open!

 

+993 on the belts idea.
I had the misfire codes popping up a couple of years back and it was driving me nuts. I was told many of the other items listed here (injectors, sensors, etc) could be the problem.

A very well respected Porsche guy told me to replace the belts with Porsche branded ones (the kind you get from the dealer, not some other supplier claiming OEM).
It did the trick. $60 bucks and problem solved!

I resisted it at first b/c it doesn't make sense, but there's something about the Porsche belts that work while the others throw the misfire code. Start with the cheapest solution first... put on belts purchased from a dealer that say "Porsche" on them.

 

I had misfire codes every so often, usually after high revs; turned out that I had two spark plug wires switched easy fix for me though heh.

 

All those wires,.....so little time,...

 

Getting ready for Smog and just was able to clear my readiness codes but have these misfire codes (across all cylinders). Will this cause me to fail smog? My CEL is not on. TIA

 

what's your car year
maybe the PIWIS cable can fix it up.

 

++ on getting the belts right. After my mechanic made the change to my 96 C4, a CEL is rare. He said even a little variation in belt movement can set off a CEL. And yes, use factory belts.