Dear Tom and Ray:

I have a '93 Toyota pickup with a six-cylinder engine. I live at 6,000 feet, and when I'm there, my truck runs fine. But when I go down to sea level, the truck is very hard to start. It cranks but has a hard time turning over, then when it does finally turn, it runs roughly until I get the truck on the road and the RPMs are up. Then it runs fine. Right now I'm staying at a friend's house that is at about 1,000 feet elevation. I can start the truck fine up here, but as soon as I go down to sea level, it becomes very hard to start, whether the engine is hot or cold. The elevation is the only variable. Any ideas?

-- Celina

TOM: Well, first you have to tell us how long the "Check Engine" light has been on, Celina. Then we'll decide how many yards to penalize you for "withholding information."

RAY: Problems like this rarely occur without the computer setting a Check Engine code. So if your light IS on, you need to have the vehicle scanned for trouble codes. That'll usually help pinpoint the source of the problem.

TOM: If the Check Engine light isn't on yet, perhaps because you spend limited time at sea level, where the problem occurs, then you may have what's called a "pending code." That means the computer has detected a problem but it hasn't happened with enough regularity to set the Check Engine light yet.

RAY: But a scan still will tell you if there's a pending code stored. So next time you're at sea level, while you're experiencing this problem, take the truck to someone and have it scanned.

TOM: My first guess would be that you have something like a faulty air-flow meter. But we don't have to guess. Your car's engine management computer knows what's wrong. Ask it.