Timing 25 degrees is that even possible

[JPERL]

I picked up 3rd 89 new old van for free and the previous owner could not get it to pass emissions and did not want to deal with it.

The mechanic evidently said the timing was 25 degrees advanced but yet the engine runs great no pinging or detonation that you would see with timing too advanced and has great power with no rough idle and no hesitation. No check engine lights and no codes. Engine performs great for 247,000 Miles

Is that even possible for the timing to be that far off and the engine still run as good as it does?. He said the timing was off from probably a bad TPS which would be true however I have none of the symptoms of a bad TPS acting up like surging idle, stalling after quick stops none of that

The NOX gas was high but border line. The cat is rusted out. My thought was replacing the cat and I should be good. Any thoughts on this?

[Ace MM]

The cat would be the place to start if it runs well yet fails.
TPS could be faulty and sending codes. Those have to be clear as well to pass.

[djshimon]

Clear codes.
If cat is rusted out then yeah, I'd replace and go for it.
Maybe the distributor is a tooth off and that's why the timing is so far forward. Check the timing yourself to verify first.

[Rudy]

It would run like crap, if it were off a tooth. If the timing light is showing 25 degrees off and the engine runs that smoothly, I would suspect that the harmonic balancer has spun. This would make the timing mark inaccurate. If the cat is rusted out, your probability of not passing emissions would be high.

[wavegobbler]

My timing was off 180 deg and the van ran well. Like what Rudy said, my pulley had spun.

[JPERL]

The timing was not determined by the use of a timing light but by the probe attached to the No. 1 lead spark plug wire from the emissions testing equipment so the theory of a spun harmonic balance can be ruled out

[Rudy]

Maybe someone else can chime in here, but I fail to see how you can check timing by just a probe on plug wire #1. Isn't an inductor on plug wire #1 just a reference point for when cylinder #1 is firing? It doesn't show where the engine's rotation is when that plug fires.

How would an emissions place see the degrees of rotation on an engine at the point where cylinder #1 fires, especially on a 1989 vehicle with no fancy computer to give you all the data?

[JPERL]

That's my suspicion too. I was just relaying what I was told by no means do I believe any of it since I was not there to see the emissions test

[boogieman]

getting my rebuild together and harmonic balancer has spun about 90 degrees...id say anyone timing their engine needs to verify tdc...im very reluctant to run this pulley even with my new marks...sadface

[Flecker]

I'm gonna make a guess that he didn't short the test terminal... without the test plug shorted it will happily run at about 25* btdc.