Cam Deviation

[FriedEggs]

Hello all, First time posting but often found answers to my problems on the forum. My experience has been gained by tinkering with a few cars I've owned and I'm not a professional. I'd like help to understand the reading I get from Durametric relating to the camshaft position at the crank. Around three years ago the reading was 3 degrees then moved to 9 last year. The 9 degrees of cam deviation holds steady at all revs. I understand the acceptable limits are +/- 6 for my model. I'd like to add the IMS bearing has been changed. The car was and still is running well with no check enigine lights. I did have a fault code P1531 which led me to investigate further using the information provided on the forum

 

Again using Durametric I was able to activate bank 1 and 2 cam actuators individually, both causing the engine to run rough therefor my understanding was both were working as intended. I then removed all green plugs and checked the timing as described in the Porsche workshop manual, again no issues found there either. My thoughts then moved to excessive wear on the camshaft actuator pads, since the deviation had moved that made sense to me or possibly a failing actuator. As I had already invested so much time investigating the issue I decided to change the cam actuator pads now rather than later but before opening up the engine I replaced the camshaft and crankshaft sensors but the deviation reading was still the same

 

Both Bank 1 and 2 cam actuator pads have now been changed, bank 1 set were slightly more worn but both sets didn't look totally used up. Both cam actuators looked good and no sign of failure to the green o ring seals. To prevent any future issues I changed the solenoid on bank 1 as it looked badly corroded from the outside

 

So to my reasoning the camshaft position at the crank should now be 0 degrees +/- 6 but it still is 9 degrees. I have now driven the car a few thousand miles with no issues or change to the cam deviation. The fault code has never reappeared

 

My questions are isn't 9 degrees outwith the factory specification and the check engine light been triggered at some point, should the cam deviation at least have returned to 3 degrees with the new cam actuator pads fitted and is it still possible the cam actuator isn't properly functioning

 

Apologies for the long story and your help is appreciated 

 

1998 996 C2 RHD UK spec 55k miles

[JFP in PA]

P1531 indicates a problem with the cam adjuster on bank #1, indicating that it is not assuming the active position.

 

Possible causes:

 

• Open circuit on triggering wire
• Open circuit on B+ supply wire
• Faulty actuator

Diagnosis procedures:

1. Check B+ power supply wire for voltage, repair wire if necessary
2. Check trigger wire for continuity, repair wire if necessary
3. If both are OK, replace actuator

 

 

[FriedEggs]

Thanks for your reply

 

That fault code hasn't shown again since I cleared it at the time of changing the cam pads but If the actuator is not assuming the active position even intermittently would the car run badly at certain points through the rev range? Also could I see any other evidence of that i.e. fuel trim etc?

[JFP in PA]

Not necessarily, you would have to catch it in real time to see any difference.  And, as all the diagnostic tests are electrical in nature, it would be worthwhile running them to make sure you do not have a simple wiring fault.