Rouxzy

Have a '90, 3.6 transplanted in my car and the problem that just started is that when I'm accelerating hard in any gear the engine starts to skip, (sometimes hard), as soon as I go over 4000 RPM's. Any possible solutions is welcomed.
Tom

Steve Weiner-Rennsport Systems

Tom,

Assuming for the moment that the ignition system is in perfect condition, it sounds like a fuel delivery problem.

Make certain that the fuel filters are clear, external and the in-tank one. Then, check the fuel pump's volume.

evoderby

How old are your plugs? Worn away electrodes / large plug gaps can lead to the symptoms you describe as the spark simply gets blown out under circumstances with high dynamic compression i.e. WOT around max torque.

I experienced the above once during a rolling road session, wasted 30 minutes of finding the cause, leaning the mixture seemed to improve matters slightly.....until we measured plug gaps and tapped things back to spec, problem solved straight away.

Good luck!

Laker

also, Adrian's book mentions that a bad DME relay can cause power loss at...4000RPM

Rouxzy

Plugs, caps, and rotors new last summer along with the fuel filter. Laker, what you said about the DME relay has got me thinking. The relay that came with the engine that I've now had for about 5 years quit on me last week. I popped in my backup and I was on my way, and now that I think of it the problem with it cutting out just started in the past week. I'll try putting in the new backup DME relay and see what happens.
Thanks
Tom

johnsjmc

I chased a similar cut out on a 1990 3.6 I installed in a 1980SC.Cut out started out of the blue with no warning or apparent degradation of performance just an annoying momentary cut. I replaced DME relay,plugs,caps rotors,belt,and both flywheel sensors. I even opened the DME and reflowed a bunch of suspicious looking solder joints. After each change I thought I had found the culprit. I eventually replaced the plug wires. Even though I could not detect a miss or any leakage in the dark. The plug wires fixed it. Looking back I believe the twin plug set up covers up a missfire as one plug still fires. Some reading on Pelican suggested the 964 DME is particularly sensitive to RF interference and might have been rebooting.

Rouxzy

Problem solved. I replaced my spare DME relay with my new spare and the problem went away. What's disappointing is the relay that was bad was a relay I bought 5 years ago as a spare. When it comes time to use the spare I find out it is faulty, and being 5 years old there is no way of getting credit back from vendor. So I guess lesson learned here it to test your backup relay before tucking it away in the glove box.
Tom

KaiB

Problem solved.

Interesting and good for you. I'll file this away in the "one of the first things to check out" list as it could save a lot of troubleshooting.

Laker

just for reference, page 387 in Adrian's The Enthusiast's Companion lists 8 symptoms of a bad DME.

Rouxzy

I've heard of Adrian's, "The Enthusiat's Companion", but what is it and where can I find it?
Tom

Laker

It's 964 specific
http://www.amazon.com/Porsche-911-96...6249063&sr=8-1
so covers your engine and ECU

RSAErick

Interesting. I think I need to put that new DME in to see if it helps my performance probs (stalling and poor engine performance). I thought that the DME would be a longshot, but maybe not! Anyway, glad that you got it solved.