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Dear Jim,

I have a 1996 GMC conversion van (5.7L V8) with about 176,000 miles on it. I had a complete tune-up performed about six months ago, but the van is still having trouble accelerating up even slight inclines. I was thinking it might be a dirty fuel filter, but a guy at the dealer just did some diagnostic tests and said he couldn't find anything wrong, and that I'll probably need a $650 tune-up to correct the problem. This sounds excessive to me, but I don't know. What do you think?

Greg Lindsay

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Oh, I think the tune-up sounds excessive too, bro. If the one you got six months ago was done properly, why would you need another one now? And what kind of tune-up costs $650? A standard job -- plugs, wires, cap, rotor, filters -- should be at least $400 less than that.

Most importantly, there's no reason to believe a tune-up will solve anything in this case. I think you're looking at one of three possible problems here: low fuel pressure, a partially blocked exhaust system or a clogged fuel injection system.

When you're driving uphill, you're putting a heavier load on the engine. If your van is struggling, it's either because the vehicle isn't delivering enough fuel, or it's not pushing enough exhaust. Good guess on the clogged fuel filter, bro -- check that first, because it's a cheap part. Then again, it could be clogged fuel injectors themselves that are causing this, which is a pretty common issue with this kind of vehicle. Dirt, sand and all kinds of other debris that accumulates in a gas tank can eventually make its way to the injector nozzles and kill their efficiency. A lot of shops can cure this now with a high-pressure flushing system.

It's also possible that you have a bad fuel pump, which is a more serious repair ($250) that involves removing the gas tank. But if your fuel pressure and injection both look OK, I'm guessing it's the exhaust: either a bad muffler or a partially plugged catalytic converter. Whatever it is, that $650 tune-up sounds like the worst choice you could make.

Tip of the Week:

Drivers, never fill up at a gas station while it's being refueled by a tanker truck. Those high-pressure transfer hoses tend to stir up all the garbage that's settled at the bottom of the underground storage tanks over the years -- junk that will go straight through the pump and into your own vehicle.

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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.