lwporsche

The 10 year love affair with my 1990 Porsche 964 C2 has recently been soured by a problem I have yet to resolve / understand. About two weeks ago on a very cold morning (7 deg F; cold for Chattanooga,TN) the car began to surge shortly after starting and couldn’t be restarted. It would turn over normally but not run other than a sputter. I had it towed to the small shop that has historically done a good job and the mechanic previously worked at a local dealership. After 2 days he reported he was unable to identify the fault and replacing parts was cost prohibitive. A Bosch Hammer revealed only one code for the Hall sensor in the distributor. The mechanic said he didn’t think the Hall unit was bad but suspected the ECU. His testing revealed the spark was intermittent. I sent the ECU to Florida (Specialized ECU repair) for a test / rebuild and was informed that the ECU tested good and was not the source of the failure. When the ECU was returned the car started and ran for a short period (20 minutes) before sputtering to a stop. On some questionable advice I replaced the engine speed sensor at the flywheel because of high resistance; the new one from the dealer also tested infinite for resistance. The DME relay was replaced to no avail. While the engine would run I verified the coils and ignition control modules (twin distributor) were good by running the engine with all combinations to only the primary distributor. The distributor drive belt is intact and replaced about 10,000 miles ago. The car has 75,000 miles on the clock and the engine is stock with exception of a K&N filter, a B&B muffler and cat bypass, and a Weltmeister chip; all installed several years ago. The car presently will start after sitting for a day but stall after a couple of minutes preceded by erratic engine speed. I feel a trip to the local dealer would be an unsatisfying experience$$$.

ltc

Can anyone offer any suggestions, ideas, help or comments to this new RL user?
Thanks in advance.

jimq

Oil on the MAF from the K&N filter?
Oh yea welcome and where are the required pictures of the car

DAVISRILEY

Have you checked fuel pressure? Would be curious to see what it looks like. Almost sounds like a bad fuel pump, but I would not be willing to put any money on it.

sundog

See if you can check the fuel pressure. I think that there is a gauge that you can have attached while it is running. Fuel pump would be my guess as well.

Wachuko

How did you test the coils... sounds like you should see if a friend can let you use a pair and test them that way...

I second the suggestion of checking fuel pressure...

Indycam

Fuel or spark ?
If you use starter fluid will it start up ?

Oracle

take it to a different place.. sound like you need a better opinion. (extrapolate your 964 situation with a medial condition)

newsboy

Even if you test your coils, and they test within Porsche specifications, they can still have internal problems,
that can cause electrical problems, bad running, limp home mode etc.. It happened to me. If you do it yourself, coil replacement is around $100.00. perhaps, worth a try?

Wachuko

That is why I asked how he tested them... If the original are still in the car my suggestion is to replace them and test. That is, after checking the easy stuff that requires no expense other than time to test... like fuel delivery.

dutchcrunch

hello, replace dme relay, its cheap.

if no help i suggest that your flywheel sensor is bad.


you have dual ignition system and i would HIGHLY doubt that both would go out at the same time.

dutchcrunch

i am to fast to post and slow to read. seen that you already done my suggestions.

dfinnegan

You say that when you start cold it runs, but dies after a couple of minutes.

It's interesting to note that the O2 sensor kicks in after about 90secs; when it's warmed up. Try disconnecting the O2 sensor and test again.

The connection is inside the engine compartment, to the left, down behind the blower unit. It's clipped against the fender, down and forward as far as you can get. The wire runs through the tin-ware and out to the O2 sensor mounted in the top of the catalytic converter behind the left rear wheel.

It can be reached without removing the blower, but the first time around it will be much easier if you pull the blower motor and tube (two 10mm bolts on left side of blower motor, jubilee clips-same as hose clamps, wire connector on left side of blower, couple of wires on blower tube).

cwrm4

Possibly a clog/restriction somewhere on the suction side of the fuel pump, which could cause the pump to cavitate (and make the pressure fluctuate) after a couple minutes of the car running.

lwporsche

Thanks to all of you for your suggestions. I did get the car to run on each coil to a single distributor believing this verified each coil and ignition control unit as functional. A new DME relay did not help neither did a new crankshaft speed sensor; I think my car (1990 C2) only has one. The O2 sensor is something I haven't tried. The servicing mechanic did verify fuel delivery by disconnecting a test connection on the fuel rail though I don't know if he measured pressure. I'm a new subscriber, not terribly computer literate but will get a photo on line when I get my car back on the road. I offended the community by having the car on a flat bed twice on its journey back to my garage!