I have a 99 Bonneville SE, all stock. The car runs rough intermittenly, but mostly when it'* cold or has only been driven for 30 minutes or less. Once the car'* been driven for an hour or more it'* fine. Weather doesn't seem to play a factor in its performance either. It seems that when the RPMs are greater than 2500 it seems to miss and the transmission slips. The car has 53,000 miles. I am going to change the spark plugs, wires, fuel filter and air filter. I don't think I have a transmission problem here due to the lower mileage. About 1,000 miles ago I was getting a Cylinder 2 misfire from the computer. Does anyone have any other recommendations??

:?

I/m having the same problem you are. I took it to the shop and they told me the #3 plug wire was bad so I changed out all the cables and it didn't fix the problem. It'* back in the shop today. I have ran fuel injector cleaner through it and it didn't seem to help at all. I'm wondering if it isn't a sensor or the coil pack. Please let me know what fixes your'*. Thank you!

Yup. No shop in the land can tell you whether your miss is from the #3 plug wire or the #3 plug. It could be either. Even new plugs can fail early, or get fouled by another problem.

Plugs and wires should be replaced together for a problem like this. Plugs are cheap.

Could it possibly be a cam sensor? If this is faulty or intermittent the timing won't keep up, or will it?

I had a problem close to yours, i have a 1994 Bonneville SSEi I had 7 MPG and there was lack of power in my engine on top of it the supercharger was wacked out and the boost meter would goto -2 lbs, i took it to the shop and they told me that they balanced the harmonics i'm not positive what that means but now the car works like charm

I just had my 97 Bonneville in the shop and the tester/computer they used to run diagnostics showed no codes but the cam sensor light kept flashing. The mechanic told me that this light should stay on. :?:

The light was on their tester. You make sense in that you'd think the light would blink every time the magnet passes the sensor. Maybe the magnet is to weak. I have heard of the magnets not holding up. My car does have 120,000 miles on it. What type of platinum plug is best for the 3800 6 cyl? There are bosch platinums in there now. The dealer told me that they get better performance from the ac delco plugs. I don't know if that because there a GM dealer or because it'* true.

Yes go with AC-DELCO or NGK spark plugs. A lot of people here do not like the Bosh plugs. I got the AC-DELCO Professial Irdiums spark plugs and work great.

Damn, a mechanic told you to ditch the Bosch for the Delco'*? Trust that guy with your life AND your car. Sharp feller.

Absolutely. The Buick 3800'* we run eat bosch plugs for breakfast. They don't last long.

As far as the cam sensor.....Even if it was at idle, I seriously doubt the human eye could even see a flash of the detection circuit from ONE cylinder reference, let alone all 6. You're idling at about 750 rpms or so. That'* 12.5 flashes per second.

Don't forget that if all your replacements do not solve the problem, running rough, intermittent idling could be the result of a dirty throttle body. Just a thought........