Joey T

I have the front cover mostly off this weekends donor. It *looks* like the cam timing is one tooth off.

When I bring the crank to TDC the timing marks for the cam are exactly one tooth off. I can verify that the TDC mark for the crank is correct ( took the number one plug out to verify TDC .


The car has 90k. I see no evidence of the timing belt being done. Here are the options as I see them:


1. Someone has done the timing belt and it is one tooth off.

2. Someone has done a cam chain tensioner and taken the cam gear off. Then they put the cam gear on one off.


I plan to take off the valve cover and check the cam alignment marks to verify cam timing before putting it together.


My question is... can you clock the camshaft sprocket wrong? IOW, is it ppossible the last guy in there put the cam sprocket on wrong?

qazimo

or can the timing belt actually jump a tooth keeping in mind the mileage?

jprice@CPS

Are you checking the timing with the cam chain tensioner working properly?

Joey T

The only real question is if it is possible to have the camshaft sprocket installed on the cam in any posistion excpet correct.

I know on my 2.8 that it is not indexed in any way, so you can bolt the sprocket on randomly.


What I really need to know is if I can trust the cam sprocket marks or if I need to check cam timing in any other way. The bently is unclear.

I have a spare head here, but it is an AEB. I have never needed to change a cam seal so I have never had a sprocket off.

qfrog Ti20

going to be real hard to put it on wrong.

Joey T

Thanks. Saved me from pulling a valve cover.

JHam_CT

I changed my timing belt last month, and like an idiot, I discovered that I was a tooth off after I took the car back apart the next day. The car idled fine, and even drove around the block fine being a tooth off, but a CEL came on the next morning.

Ironically, this is what the code said, "Retard set-point not reached (over-advanced)." Sometimes the cam sensor sends an intermittent code, but this wasn't - I was pretty sure I was off as soon as I read the code. Mine's an AWM, too, btw.

Hope this might help - good luck

Joey T

The cam timing in my case was most certainly a tooth off before I started. The car has a metal impeller on the water pump and some signs of a previous water pump repair.

I verified TDC by using a long 1/4 drive extension in the plug hole. I considered using a dial indicator, but in the end the extension was more than accurate enough. I verified that on a 1.8 the cam gear can only go one one way.

The car set a code for cam timing advance not reached after running it to blled the coolant. I can only assume that the PCM corrected and learned of the retarded cam timing over time and was simply pissed that I had corected it. I cleared the code and it has not returned.

According to the owner the car returned better gas mileage and was slightly stronger after the repairs. I might add that we did a lightweight crank pulley at the same time.


For anyone doing a lightweight crank pulley, the current part number for the pulley bolts for a 98.5 fit the lightweight pulley much better than the stock pulley bolts.

JHam_CT

I bet you're right about why you got the code. Adaptation. If it's true, that would be pretty impressive - the ability to compensate timing up to a tooth. Audi and VW do say that they prefer the belt vs. the chain for the higher precision.

I think I saw a post in the archives about someone being off a tooth and not knowing it until the belt was changed again. What made this customer come in for repair? Just a belt and pump replacement?

Joey T

do his belt and also show him how so he could do it himself next time.

Anyway, his car has 90k on it, 70 or so when he bought it, and he wanted to be sure.