JasonAndreas

What model year is your 964? Do you have a check-engine light? Have you tried the gas pedal method that checks the ECU for fault codes?

red911c2

My 1990 did the exact same thing. Bucking is a good term for it! In my case, the independent mechanic (Joe Vatter in Largo, FL) kept the car for a week and finally decided it was the coils. I know you said they seem ok but those are the exact symptoms that my car had. Good luck!!!

Euromagination

hey jason.

it's a 1990. no CEL (or any other lights for that matter). i didn't try the gas pedal method because i thought that was for '91+ 964's.

or am i misinformed?

cheers...

Euromagination

yeh i know what you mean about thinking it's the coils.

i actually have both coils right here on my desk next to me right now. i measured the resistance on both of them and it was fine. they also both provide spark last i checked. i'm not sure how else i can test them to see if they're bad...

??

if the resistance test checks out fine, can a coil still be bad somehow?

i *wish* it were the coils. they're cheap as hell and easy as hell to swap!! just seems to me that after these tests, they're fine...

parsecnc4

If you are not making any progress and members' past experiences have been with coils, why not just change them and see. As you said, they are very inexpensive and will be due to replacement soon or later. If your car has 60K+ miles, I would change the coils as a preventative anyway. The same for the DME relay if you have not changed it yet. All the time spent in troubleshooting would easily cost more than the costs of the coils and the DME relay can always be a nice spare.

greenjt

I had a similar problem to yours. I never really diagnosed it but switching the primary and secondary coil leads made the problem go away. It's now been a few months with no symptoms.

Odd thing is that about a year prior to having this problem i switched out my coils and leads to eliminate my Xmas tree effect on the dash but hadn't touched the wires since. then one day the car bucks and grows increasingly worse. With the help of this board (and a BIG thanks to Indycam) i worked through troubleshooting the problem until a simple swap of the wires made it go away. Try it.

Euromagination

So the car just started up perfectly!!!!! (knock on wood...)

All I did was clean off the posts on each coil, then i installed Coil I in the II spot, and Coil II in the I spot--switched them, basically.

Hooked the wires and plugs up, connected the battery, and the C2 started right up like it was brand new. I let it idle for about ten minutes, but didn't take it on a cruise since I don't quite trust it yet and the driveway is too steep to get back up if i pull out and the car cuts power. Last time we had to use a good ol' Cummins Turbo Diesel to pull the car up the driveway...

I suppose I'll be ordering new coils now. Praying this is the problem since everything else has checked out fine. Distributor parts are new, wires are new(er), plugs are literally two weeks old.... it can't be much else!!!


-Harry

dfinnegan

Congratulations! I was just asking Mel about Saturday, too. She was a go. I'm thinking we'll drop the kids of at Grandma's and go for a ride anyway!

Let me know if you still want to run the Hammer, or have access to the shop manuals. We'll need a destination either way.

All the best,
Dave

Indycam

Would santa cruz be to far afield ?

dfinnegan

That'd require Sunday, too!

Red Line

Looks like you fixed the little gremlin............Congrats............

Peter Badore

You have to wonder if the two 944 coils that are used for the 964 application are suitable for the heat generated in the left front side of the 964 engine compartment (both the 964 and 944 use the same part number coil and the 944 was the first application). In the 944 there are relatively few reports of the same types of coil caused driveability problems. In the 944, the coil is located in a much cooler location near the front of the car and away from the heat of the exhaust manifolds. I have never had had a no start coil failure in the many 944 that did have other no start problems. When the 964 was replaced by the 993, the coils were moved to the rear of the engine compartment and the ignition control module went forward to under the left seat. Maybe Porsche saw the heat load was too much for the ignition coils and control modules or maybe they were just moved to permit space for the dual 993 dual exhuast.? Either way we now have another spare part to keep on hand in addition to the DME relay. But they don't fit the the glove box as well!

unclebilly

OK so I am new here but I've been around Pelican for a few years.

I set the valves on my 90 C4 Yesterday and now it is doing sometyhing similar.

In addition to setting the valves, I also changed the plugs and put dielectric grease in the plug wires (which may be my problem). I also changed the air filter and the oil and the caps and rotors.

The car ran fine before I did any of this work so this is a new problem.

My battery was dead so I had to charge it. I went out and fired the car up last ni9ght after it charged for an hour or so and it idled just great.

This morning, i went out and unplugged the charger and attempted to take her for a drive. It ran fine for the first minute or so and then started to buck and miss. It seems to have gotten worse.

I am going to try cleaning the grease our of the leads an see if this helps. Any other suggestions? I do have a durametric (still in the packaging).

Richard Curtis

UncleBilly: Try cleaning all the electrical grounds. You might also try a new DME relay (You do carry a spare with you, don't you?).

greenjt

maybe try new floormats?