"Shep" > wrote in message
...
> Ted, true if it is fuel contaminated especially, in respect to hyrocarbons
> only.

Yep, I should of asked if it just barely failed or not, as there's tricks to
getting it to pass.

I myself has a '84 Celebrity and it just barely passes on HC's. Sometimes
it fails. The engine is the 2.5 with the GM computer-controlled Varajet
carb, the engine probably has about 260,000 miles on this carb (the
engine has been rebuilt) The converter was replaced once by a former
owner and is probably close to being shot again.

I'm kind of cheap so what I do when it fails is just go to a differnet
testing station. The last time I had to take it in, it failed HC, so
that same day I drove to another test station, which was about 15
miles away, out in a rural area. I basically drove 70Mph on the
highway to get there, then the test station is right off the freeway
exit, and nobody was in front of me, so I got it tested within
minutes of coming in off the highway and it passed.

The test devices are supposed to be recalibrated periodically
but I think there's enough variation that this trick works if
it's a borderline fail. Also the testing stations I used were
at different elevations.

Aother thing you can do is just try testing it on a different day
that has a different barometric pressure.

Most people focus on fuel modifications to try to get borderline
engines to pass, but air modifications are often more effective
since a lot more air is going through the engine than fuel. The
idea is that different densities of air may change the pollution the
engine puts out. With computer controls of course the engine
tries to compensate for this, but it's not perfect. And older
cars without engine computers are particularly easy to trick.
My father had a station wagon once that would pass if you simply
removed the air filter before going in to have it tested.

Ted