Stumped on 97 Bonne Condtion

[loco12348]

The car broke down and since replacing the water pump, my 97 Bonneville is experiencing the following problems:

1) Engine Light is On - It remain steady and blinks occassionally
2) Engine Idles real low and when I shift it into gear, it sound like it wants to stall.
4) The car hestitates on acceleration at times
3) Runs very good while I'm not idling or accelerating

From what I've read through the message board and spoke to friends is that it could be a bad/warped valve and a compression test is necessary to determine the problem, Power booster could have a vacuum leak, or the Computer is bad under the passenger's side dash.

I have replaced the wires and pluge, water pump, and tested the coils. Last year I had some transmission work done. Nothing appeared to solve the rough idling condition while in park or drive. I am hoping the a fuel/carb cleaner can help.

Please help with any suggestions or ideas...Thanks

[86TATpi]

I would take it to Autozone if you can drive it. They'll hook up and get any trouble codes that may be stored. A bad PCM may cause these problems. But so can a number of other things. A bad idle air control valve, compression leak, etc.

A compression test would be able to tell you if you had a valve problem. A vacuum gauge would tell you if you had a vacuum related problem (could also be a valve causing the vacuum problem)

Check the condition of the spark plugs and the wires. Does the car seem to be missing? It's possible a cylinder balance test can point out the bad cylinder. OBD-II is very sensitive so a number of things can cause the problem. I'll check to see if there are any TSBs on the problem. Good luck.

[86TATpi]

One other thing. When the car broke down and needed the water pump replaced, was it over heating? Check any wires around the area you were working. If the car overheated you may have some burnt valve(s) or other related problems.

[loco12348]

Thanks 86....We did a compression test today and found that the 2 and the 4 cylinders pressure wasn't what it was supposed to be. I don't feel like doing any engine work and it may be too expensive to have it fixed.

[86TATpi]

Beings it is the 2 and 4 cylinder it sounds like a head gasket may be the problem. Or cranked head or block (most likely the gasket). I would have a leak down test done on those two cylinders especially but you can do the whole engine. If you were to buy one you would need an air compressor and the tester. The test requires that the cylinder being tested be at TDC on the compression stroke. Remove all spark plugs, oil filler cap, pressure cap, dip stick, and block throttle plates open. Apply 100 psi of air through the tester which is screwed into the spark plug hole. In this case the 2 and 4 cylinders would have close to the same reading and if it is the gasket you would feel air escaping out of the other spark plug hole. Otherwise if it came out the
throttle body = intake valve
exhaust = exhaust valve
radiator or surge tank = head gasket, cracked head or block
oil filler cap or dip stick = damaged rings, piston, cylinder wall
adjacent cylinder = head gasket between two cylinders head or block

You said you didn't want to work on it, but, I figured maybe it would help someone else.