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I just failed a smog but the guy said I was very close to passing. Its a 1990 Suburban, 5.7 L, V1500. I did a little reading when I came home and it sounds like the problem might be the idle air control valve instead. I have noticed that when I am at stops the RPM gauge will rise a bit and then fall to where it was.
The guy also said my problem might be that I didn’t drive it long enough since I haven’t drove it since Saturday and also only live 5 minutes from the place.
My question is should I try a few things before even messing with the cat? A few thoughts are that seafoam and some TBI cleaner spray might help.
This are the numbers from the smog:
[IMG]http://i62.tinypic.com/117eft0.jpg[/IMG]
The first bar is at 15, the second at 25 mph.
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Sounds like maybe a good highway run would be in order. Maybe a good 20 to 30 minute round trip on the freeway. Also, is it expensive to get tested? If it is but a few bucks, I would gamble trying that. If it is not cheap, well then see what is up under the hood.
Well a few things so people might help more –
Is the check engine light glowing?
Whether it is or not –
Have a place like autozone pull the engine codes.
You may not get any if the CEL is not lit, but this would be the place to start. It costs nothing and gives more direction.IACV seem to be a problem on a lot of engines for whatever reason. You could probably clean it to see if that at least smooths out the idle fluxuations.
As far as messing with the cat, I would personally investigate and try other solutions first before dropping a mint on a new cat.
The first retest is free for sure. My plan for the time is to drive it plenty and then test it again either tomorrow or Friday.
Hydrocarbon is unburned fuel so if your truck has a misfire, vacuum leak or over advanced ignition timing it would fail on hydrocarbons.
High Co. (carbon monoxide) is caused by partially burned fuel so if your truck is running rich it can cause a Co and hydrocarbon fail as it can’t burn all of the fuel.
If you have never replaced the oxygen sensor it could be throwing the mixture off to cause an emission fail but not enough to cause a check engine light.
The catalyst is the last thing I condemn on that type of failure.
Make sure you have a fresh tune on the motor. cap , wires, plugs , oil change and air filter ( you would be amazed how this helps )check for a low idle miss ( vac leak ) especially check tb to intake mount gasket ( like to burn out at the rear of the tb ) make sure to get the cat good and hot before having the test ( 30 to 45 mins of freeway driving ) of course you are in the LA area so you may not get too far on the freeway in that time LOL , I am in so cal ( sandiego ) so I can relate. fact is cali is making it harder every year for older vehicles to pass .
619DioFan, that is one thing I’ve been thinking about lately. It’s absurd. Los Angeles and California are the perfect combination for making me hate my life as a driver of an SUV.
Wysetech, thanks for clarifying more or less what those numbers mean. I don’t believe there are any vacuum leaks or misfires. But I’ll have to get a mechanic to look at it and see everything you both mentioned. It did have a tune-up in mid/early August. That brings down the amount of things to look for, I think.
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