what would be the consequence of a cambelt jumping 1 tooth & is this a plausible thing to happen??

 

Hi,
Yes it is possible, WRX 01 + are sensitive to that problem (North America) Subaru has fixed the problem this year by installing timing belt guide on each cam. The results of a tooth out are: bad idle, maybe CEL code: missfire cylinder 1-2-3-4. bad fuel economy. At high rev, you are not supposed to notice any differences. That about it!
Cheers

[Edited by fmessier - 8/20/2003 2:13:36 PM]

 

My 99my had such guides
JohnD

 

My mates type R has developed a tapping noise from N04 cylinder, on removal of the HT lead & starting the engine, the tapping dissappears, the garage has stripped the rocker covers off & have reported to him that the exhaust valve is out of timing by 1 tooth, so, could this cause the constant tapping?

 

Removing the ignition from the cylinder is unlikely to affect any tapping from the valvegear. The noise is more likely to come from the piston or bearings for that cylinder. If the exhaust camshaft is mistimed it will be the same for both the cylinders on that side anyway.

Les

 

If the tapping noise goes away when the ht spark is removed, possibly sounds more likely to be piston slap/ little end bearing, rather than timing out.
The only way I've ever seen the timing jump is either by belt tensioner failure or by push starting down hill, but that was only on an early engine without the revised belt guides [to stop it jumping off the timing gears], which was fitted to Uk engines from 99/00 change over.

Suggest they look a bit further, as yes, the engine would run lumpy anyway with timing out untill reaching high rpm.

 

Doesn't the engine let go if the cambelt slips? Won't the valves be pushed into the cylinders heads path? Thought thats why its so important to change them!

 

Thats right Jza

Les

 

"Doesn't the engine let go if the cambelt slips? Won't the valves be pushed into the cylinders heads path?"

Only one tooth out, no troubles, but more than three teeth, some valves will bend for sure!
cheers!

 

The car is now back out of his brothers garage, the cambelt looked a little spilt in places & has now been replaced & retimed & the noise has dissappeared, very strange!! tapping cambelt???

 

how about up to 3 teeth on 3 cams?

 

three teeth on each cam is the maximum slip that the engine can get, more than that, you are in big trouble!! If the engine has slip three teeth, ignition is impossible, the engine won't start up!
cheers