I made a huge mistake My car was running rough...

Dear Car Talk

Dear Car Talk | Apr 01, 1996

Dear Tom and Ray:

I made a huge mistake. My car was running rough, so I used a $29.95 coupon to get a tuneup for my '82 Toyota. I walked out $150 poorer with a "diagnostic tuneup," an "induction service" and a car that was still running rough. They said the car was running on only three of four cylinders. Since then, I've had the fuel filter and the PCV valve changed, with no improvement. My dad and boyfriend are both mad at me for spending all this money, but they can't figure it out either. I'd hate to drive this car off the pier, but I'm starting to feel like a desperate woman. Have any advice? -- Chris

RAY: Yes. Don't drive the car off a pier. If you think your dad and boyfriend are mad at you now, wait till you get hit with an illegal dumping fine! I got one of those after I "disposed" of my brother's '65 AMC. Although it was fun to watch it splash!

TOM: I'm going to assume that the guys who did the tuneup checked your compression, because that's the first thing any decent mechanic would do.

RAY: So assuming your compression is OK, my guess is that you have a ruptured auxiliary accelerator pump (AAP) diaphragm.

TOM: When that diaphragm breaks, excess gasoline pours into the No.1 cylinder and gas fouls that spark plug, causing that cylinder to not fire.

RAY: If your dad or your boyfriend are mechanically inclined, ask one of them to remove the No.1 plug and see if it's all wet with gasoline. If it is, the AAP diaphragm is what you need.

TOM: If the plugs are clean, you may have an intake manifold leak. A bad manifold gasket would allow too much air to get into one of the cylinders. And if there's too much air in there -- just like if there's too much gas -- the cylinder won't fire.

RAY: In that way, your cylinder head is a lot like my brother's head, Chris. When it's filled with nothing but hot air, all productive activity ceases.

c 1996 by Tom and Ray Magliozzi and Doug Berman
Distributed by King Features Syndicate, Inc.

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