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Dear Jim,

I can't seem to pass the state smog test with my 1988 Pontiac Fiero (2.8L, V6).

When I tried a week ago, they said the car failed because they couldn't get it to idle at a low enough speed. I think they said it was idling at about 1,100 RPM. The car is fine except for this engine problem, whatever it is.

I'm not even sure why this is a big deal, but how can I fix this and pass smog?

-- Marc Coyne

Failing the smog check is annoying, bro, but the good news is that it's not really an engine problem you're looking at. Most likely, the trouble is in the fuel system.

Your Fiero has something called a throttle body, which contains dual fuel injectors. The idle speed motor is also part of the throttle body, and this is the part that's responsible for your car not passing the test.

That unit gets its instructions from the car computer, or engine control module (ECM). It's fairly common for the idle speed motor to go bad, and it sounds like yours just isn't responding to the ECM as it's supposed to.

The guys who do smog checks use a machine that's designed to take carbon monoxide and hydrocarbon readings at two different engine speeds: one while the car is idling, and one with the accelerator pressed (to simulate a 55 mph speed).

Their computer expects your vehicle to idle somewhere between 600 and 800 RPM. Because yours is idling at 1,100, the emissions test is automatically voided and the car fails.

The fix is simple: Replace the idle speed motor.

It shouldn't cost more than a couple hundred dollars, your Pontiac will pass the smog test and you'll be on your way. And here's some more good news, brother: Not only will you be keeping the air a little cleaner, you'll save some money on gas in the long run with that lower idle speed.

Tip of the Week

According to a recent study done by the Car Care Council, 54 percent of you are cruising around on tires without enough air.

Drivers, keep that tire pressure up. Good pressure means you're driving more safely, the tires are lasting longer and you're saving on gas.

Check them all at least once a month, and don't trust those built-in gauges at air stations -- buy your own.

Buffalo Jim, owner of Allstate Auto & Marine Repair in Las Vegas, writes a weekly column. Send your automotive questions to him at buffalojim@lasvegasniftynickel.com. If Jim picks your question to answer in Nuts & Bolts, you'll also be the proud recipient of a deck of official Buffalo Jim playing cards, presented in a classy, tin box bearing his hairy image.