Failed emissions due to timing? Can it be?

Dan Cordon cord4530 at
Thu Apr 8 11:07:05 EDT 2004

Sorry, I should explain better. You're right....the crank pulley can 
only go on one way. I'm also pretty sure that there's nothing 
missaligned between the crank position, camshaft, and distributor. If 
there were it probably wouldn't run, or if it did it would run pretty 

What I *think* has happened is that the mark on the front is no longer 
referenced to TDC. I've heard many times (Cody very recently) where the 
timing mark on the pulley has rotated relative to the keyway in the 
crank pulley it's affixed to. (deteriorated rubber?)

If this were the case, then the engine would be running just fine (and 
pass emissions great too), but when the tech person puts a timing light 
on the engine and finds the mark on the will be way off 
from what the actual timing is. Didn't Cody mention on the last 'get it 
running' quest that the mark was nearly 180° off?

Assuming this is what happened, (and the pulley with the timing mark 
isn't too loose) you could re-mark the timing mark to coincide with TDC. 
This way when the tech person checks timing again they'll find it 
perfectly normal.

Alan Cordeiro wrote:

> Dan,
> Not sure I understand where the five degrees could come from.
> 1)  The crankshaft pulley can only go on one way...not sure how
> it could go off by five degrees.
> 2)  If the pulley were off five degrees somehow, you still end up aligning
> the timing marks on the CAMSHAFT pully to the (rusty, almost invisible)
> timing mark on the flywheel. The engine reads the flywheel teeth and
> once-per-revolution pin, and uses this as the basis of timing.
> therefore, if your timing check was good....the front crankshaft position
> should not matter at all.
> Alan
>>I haven't experienced this first hand, but isn't it pretty common for
>>the front pulley to slip out of alignment? I thought I've heard many
>>people doing TB jobs and found the TDC reference had moved notably. It
>>could be that yours has slipped 5°. Just a thought anyway.
>>While improper timing can certainly give poorer emissions, you didn't
>>mention if your car passed (or was tested yet). Could be your timing is
>>fine with the pulley slipped, or it could be the ignition is being
>>retarted by the ECU too. Perhaps it's falsely detecting knock?
>>Dan Cordon
>>Mechanical Engineer - Engine Research Facility
>>University of Idaho
>>200q20v mailing list
>>200q20v at

Dan Cordon
Mechanical Engineer
University of Idaho - Engine Research Facility

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