Hi All,

 

After suffering some really bad detonation we checked my timing and found it was out by 15 degrees (30 degrees advanced at idle). Set it back to 15 degrees and the det was cured although performance was still far from peaky.

 

I can't think of any way that the timing can jump without the timing belt/exhaust cam jumping one or more teeth. We replaced my timing belt at the weekend and found everything was timed up right BUT the marks on the belt were two teeth out on all sprockets when at TDC (!?). Checked the timing again after installing new belt and still 15 degrees out with the CAS in its original position.

 

The only possible explaination I can come up with is that the ECU was stuck in safety boost mode when it was originally timed hence it was retarded by 15 degrees and had to be advanced to allow the standard 15 degrees. I've recently bypassed the knock sensor which could mean that out of safety boost it was advanced by a further 15 degrees. What doesn't make sense is that it got gradually worse over the 2 weeks before I bypassed the det sensor :( also it always performed very well when it was standard - I'm pretty sure it wasn't i8n safety boost mode.

 

I hope this is still making sense....

 

Anyone got any bright ideas?? Can the CAS fail internally causing the timing to go out? Can the CAS drive shaft on the Ex cam wear or slip in any way??

 

Any advice/suggestions appreciated.

 

Best regards,

 

RobH

 

PS - I know this has also happened on another car!!

Originally posted by RobH

 

Can the CAS fail internally causing the timing to go out? Can the CAS drive shaft on the Ex cam wear or slip in any way??

 

 

yes.

 

the cas can feck up internally, but more often the splines wear.

I do recollect hearing that the location pin on the end of the CAS shaft can wear, that could cause some variation - but 15 deg is a helluva lot !