Snowhead

I have had a slight hesitation problem @ 2000 revs and having researched the topic, I replaced the DME (no change) checked the distributor belt (intact). Cleaned the AMF and ISV (no change). Checked the coils by swapping coil leads and igniter switches and found one ran rough. I swapped out the suspect coil (from a friends 964/C4) and the car ran much better but still had a slight hesitation. On a drive tonight the car after a 10 min drive suddenly started hunting, and wouldn't idle and kept stalling and I couldn't drive any further. The car will idle on either distributor/coil on its own (1 better than the other but when the 2 are hooked up it wont run and seems as if it is running on half the cylinders. Any thoughts/advice greatly appreciated, ( I hope its something simple)

Laker

mist the engine and check for arcing in a dark garage. Also double check that all leads on both distributor caps are on the correct (OEM Beru's are numbered) contact and pressed down snugly.

DAVISRILEY

Also, check and make sure that the gas pedal isn't stuck on the floor mat, not allowing t to come all the way up. Mine did that one time when I put new floor mats in. Don't think that it would cause the hesitation, but it can cause the stalling/idle issues. Also try a throttle adaption. Check the alternator output, and the battery. Low voltage can cause some of the symptoms that you are seeing too.

dfinnegan

Have you checked that the AFM connector is not contacting metal bits in the back of the airbox?

http://www.pcarworkshop.com/images/b...0590geolab.pdf

altarchsa

Save yourself lots of hours of troubleshooting and misery and replace the coils and plug wires if that has not been done. You will not regret it!

RSAErick

Any fault codes from reading the CEL?

Snowhead

The afm wire has been tied back with a cable tie as per the TSB and the breather pipe pushed back, so I dont think that is the problem. I did have a look inside the AMF and the tracks all seemed fine with no pitting. I dodnt have a CEL so I may have to have the car put on a trailer to a local Porsche speciaist to put it on the hammer. Its really weird though as to why it will idle on either distributor but hunts and stalls when both are connected. Any other thoughts before I push it over a cliff.

RSAErick

Is it possible that the distributor belt skipped a tooth, so that they aren't firing the plugs at the same time?

Snowhead

I had thought of that as a possibility. How would you check this?

RSAErick

When rebuilding the distributor, you need to align the rotors of each distributor to marks on the case. You should see them with the distributor caps off. So, you'll have to rotate the rotors to these locations in order to determine that they are both aligned with respect to each other. And the only way that I know to move them manually, is to rotate the engine (which is difficult to do with the spark plugs in, due to compression).

Richard Curtis

This doesn't cost anythng and is quick and easy to do (plus, it might solve your problems): Remove negative battery cable both at the battery and the chassis. Clean all connections thoroughly. Reinstall. These cars (most cars) don't react well unless getting full voltage, and in my experience German cars for some reason are highly susceptible to corrosion at electrical connections.

Snowhead

I'm heading to the garage tomorrow, and will try all the suggestions and report back. Thanks to all who have contributed, much appreciated.

ThomasC2

How old is your lambda sensor? It can give you all kinds of strange behaviour like hesitation, power gaps, rough idle. Easy to changhe and cheaper than plug wires.

Thomas