Z34 Timing ??

[adaukes]

I own a 96 z34 with a 3.8L DOHC. It recently started misfiring. A code analysis told me mis-fire cyl 3. I removed the intake etc.. to get to the plug, and found the outside of the plug coated with carbon where the spark had been shorting to the head. I relpaced the plugs and it run much better, more power, ... wow. ( A leak in the valve cover gaskets has allowed oil to contaminate the plug well leading to the short.)

Two weeks later I now have a knock and am concerened the timing belt has slipped and maybe the valves are hitting cylinders.

I'v probable run the ending about a minute after I first heard it. It didn't start knocking for the first 30 seconds or so, but then continues to get worse.

Any suggestions on how I can evaluate if the timing belt has slipped ?

If it has - any experience on the damage??

Would a timing belt slip be catestrophic and cause the service engine lite to come on?

Alan

[RABarrett]

The service engine soon light may be seeing a changed relationship between the cam and crank sensor's readings. A slipped belt could lead to this issue, but unless I am wrong, does not the 3.8 use a chain? Food for thought Ray

[tankman]

the 3800 uses a timing chain... if it was out of time the engine would be really hard to start. it may not even start at all. the knock could be related to the spark plug issue you had. did you replace the plug wires as well? can you test and see if all 6 are firing? any miss, and the knock sensor will retard the timing and the engine will start to rattle and shake, and eventually stalls. what does the code show now that this new problem has come up? knocking from a misfire can cause all kinds of weirdness due to the knock sensor adding input to the control of the timing advance.

[adaukes]

The 3800 with DOHC does use a timing belt, covered by a pain in the neck to remove cover. Inspection of the belt showed no sing of wear.

After I listen carefully I became convinced the sound was coming from the power steering pump. I got a replacement.

The noise was not coming from the PS pump. Ends up the belt had one rib that was partially seperating on the inside. At idle speed the rib would occasionally flop outside the belt path and hit the plastic garding around the PS pump.

Problem solved.

Thanks