Why can our mechanic get our van to pass emissions, but we can't?

Dear Car Talk

Dear Car Talk | May 01, 1998

Dear Tom and Ray:

We own a 1984 Chevy Van, which we bought used. Since we've owned it, it has not
passed our state emissions test. We bring it in, and it doesn't pass. Then we
take it to our mechanic, and he brings it in. He gets it to pass every time. Can
you tell me what he's doing to the van to get it to pass? -- Luie

TOM: Well, there are two possibilities, Luie. One is that he's using the
technique known in the automotive industry as the "Double Jackson Method."

RAY: That's where he hands the inspector two folded-up Andrew Jacksons and says,
"Buddy, pass me, will ya?" That's illegal, immoral and unethical.

TOM: Not to mention expensive.

RAY: So it's more likely that he's playing with your timing. On a lot of
marginal cars, if you retard the timing enough, you can usually get it to pass
the emissions test. The problem is that with the spark occurring so late, the
car has almost no power, making it practically undriveable. When it's really
warmed up, you might get it to run well enough so as not to arouse suspicion.
And that's what I suspect he's doing.

TOM: Right. He gets the van good and warm, then stops around the corner from the
testing station and retards the timing. The access to the engine is right
between the seats, so he doesn't even have to get out and pop the hood!

RAY: Then he drives the thing around the corner, passes the emissions test, and
as he's backing out of the garage bay, he resets the timing and goes on his way.
TOM: And that's illegal, immoral and unethical, too.

RAY: Not to mention wrong.

TOM: Right. Other people are paying hard-earned money to fix their cars, and
you're cheating so you can drive around and belch emissions that the rest of us
have to breathe. Thanks a lot, Luie!

RAY: What you should do depends on WHY the van isn't passing the emissions test.
At this age, it could easily need a new or rebuilt carburetor or a new catalytic

TOM: So here's the deal, Luie. If you find out what it really needs and get it
done, we promise not to forward your letter to the EPA or Kenneth Starr for
further investigation. OK?

* * *

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