Pelican Detectives: Assist with CA Smog Failure on 89 3.2 Carrera

[spyerx]

Hi all, I'm posting this for a friend of mine.

Car is a sub 140k mile California car, 1989 911 Carrera 3.2.

Car is in good tune, has the 'wire' attached, New plugs, plug wiring, rotor and distributor cap, valve adjust, o2 sensor, were installed a few hundred miles ago. Car was nice and hot, car runs smooth, starts right up, etc.

Situation: Car failed with very high NO

Looking at the progression, 'something' changed for the worse. I'm wondering if there is some air leak making it run super lean? Or is it the cat? I can let him borrow my good cat, but want to ensure that's the issue before we go down that route. The drastic change and small miles between the tests makes me think its something other?

Previous 2 passed tests:


Most recent pass - a little over 1000 miles since:


FAILED Test - approx 1k miles on car from last pass to this fail

[Tremelune]

Did it sit in line and cool down before the failing test was run? How old is the cat? That does seem like a drastic change over 1000 miles.

[Matt Monson]

Winter gas?

[Techno Duck]

High NO is caused by a lean mixture. I would check for vacuum leaks. Check all the breather hoses, j-boot, intake manifold coupler, idle stabalizer hoses and also intake manifold gaskets.

[Jim Richards]

^^^this, but...

I also noticed that even though they're passing, your CO and HC are significantly higher than for the previous tests. I think that happens when the mixture is too rich. Bad O2 sensor? Combine that with Techno Duck's observations. You might have a couple of things that need to be attended to.

[db_cooper]

Could be an air leak. High NO could also be the stone in the "three way" catalytic converter is not cleaning very well too. High NO is the first clue. If no air leaks look for a fresh Cat.

[spyerx]

This is great guys. I suspected a possible air or vacuum leak. I think that is where to start.
Do a smoke test first.

[ap997s]

New CAT and O2 Sensor made this NOx polluter the cleanest '89 911 in California.

[Jonny042]

I'd suggest the OP's buddy go to the same testing station as ap997s....

[Techno Duck]

ap997s, this is my '88 with around 1500 miles on a split case rebuild. Brand new cat, probably less than 2 miles on it before the test. The stock and supply stickers on the cat didnt even burn off yet... . Seriously though, no funny business on this smog test.

Interesting that the max allowable values are different.

['76 911S 3.0]

I think that CO number is too high for a lean mixture...what were the engine temps during the testing?