Rough running - Hall sensor problem
 

My 964 C4 isn't running like it should. Especialy with low rpm and between 4000-5000 rpm. Problem is worse on full throttle. It doesn't have full power and I notice hickups. Problem exsists both on cold and warm engine (though it might be worse on a warm engine).

On the "Hammer" it showed: "Hallsignal unplausibel vorhanden". which translates (if I am not mistaken) that there is a problem with the Hall sensor and the problem is permanent.

Using the search-button showed many topics, but the conclusion is more or less: could be anything...

My question is: where should I begin troubleshooting?

Hiya Devils_son
Lots of people have had this and it most times is fixed
by finding the bad part or parts that are leaking the spark .
Id start by seeing if it will run on just one of the two ignition systems .
Will it run on #1 distributor alone ?
Will it run on # 2 alone ?

Have you looked at your motor in the dark to see sparks ?

The only hall sensor in the 964 is in the distributor. The crank position sensor is a mag sensor

Tried this and it runs on primary and secondary. Seems to be running a little bit better on just the primary.

Cylinder head temp sensor?

The Hall sensor in the distributor generates a cylinder reference signal for the DME so that the sequential injection works correctly.The motor will still run if this signal is corrupted or missing but not as well.
Could be worth checking that the signal is ok ?
Geoff

I had a similar problem with hall sensor error signal. I found out that if you have a bad sparkwire you will get such a reading. My lower plug wires were oil saturated and were shorting out. I changed out plug wires. Fixed the problem.

FWIW, I had a problem where my car ran rough and missed SOME of the time and got worse on the track. My local tech found that the aftermarket chip in the ecu had come loose!
good luck!