Questions and Answers

Mazda 626 Rattles, Barely Runs Q. Mr. Ciulla, I have a 1997 Mazda 626 V-6 with about 125,000 miles. I broke down a couple weeks back and had to have my car towed to a mechanic. When I broke down the valves started rattling and I was loosing speed before it came to a stop. It would start back up but would not idle.

The mechanic said the fuel filter needed changing, along with the fuel regulator and spark plugs. He said the fuel regulator was bad and was stuck wide open. Anyway, after changing these parts my car still wouldn’t idle and had a bad miss when driven, also my new spark plugs turned red. Since then, someone suggested spark plug wires, distributor cap and rotor. Still have same trouble.

I took it to a Mazda dealer last week. They said the machine read multiple cylinder misfire, but they wouldn’t pin point the problem. They tried to tell me I needed a water pump, timing belt and crankshaft senor and it would cost $1,200.00. Of course I took my car and left! I had the water pump changed about four months ago, so I know that was a lie, and when my mechanic changed the water pump he said the timing belt looked good.

Anyhow, the old water pump did leak for awhile before we knew about that problem, so that water pump may have caused the crankshaft sensor to be bad. I had that changed a couple days ago, and now the car will actually idle a little bit, but it idles erratically and then it does go dead.

When the mechanic changed this sensor, we also changed plugs again and they were black. We don’t know what else to do. The car idles erratically, and misses while it’s driven, also the valves rattle. Can you please give me any ideas about what could have happened?

Thank you,
Christy

A. At this point I would want to see a wet/dry compression test done. The rattling valves disturb me. I think it's important to find out what condition the engine itself is in. I think there is some basic mechanical damage that is causing the problem.

Has anyone done a fuel pressure test or pulled DTCs? If not, I would suggest that be done. There are a lot of possible causes and we have to start narrowing them down.