Cyl #1 misfire

[DEI37]

I've been running in to a check engine light on my '97 Cutlass Supreme 3100, and it's always a random misfire, and Cyl 1 misfire. If you check misfire history, Cyl 1 has about as many as the other five cylinders combined. Obviously, this is NOT good. I sprayed down the plug wires with the engine running, and that didn't tell me anything...engine didn't skip a beat, and no light show. I haven't pulled the #1 plug yet, will probably do that tomorrow night. However, I anticipate that being OK. IF it is, where do I go from there? You can feel it miss from time to time, even though it doesn't set the light. It's down on power, too, most of the time, not just during misfires, and it's a big power loss. Sometimes, it can't pull itself above 90mph .

Fuel milage has been a concern, but it's all over the charts. Some days, it's 27+ combined, other times, it's 23 highway. It's pissing me off, really. Thanks for any help.

[geoffinbc]

First thing to go after is the ignition module and coil packs. Swap the packs around for a week and see if the misfire moves to a different cylinder.

[DEI37]

I should have been a little more clear on a couple of things. When it's "down on power," it's not always missing. You know how you can just tell when a cylinder is mis-firing? It's not like that, not at all. When it couldn't pull itself past 90, it was smooth as silk, just no power. Is that still indicative of ignition?

[robby1870]

hmmmm....compression check?

[geoffinbc]

Could still be ignition yes. The spark may be weak all around. Could also be an injector symptom

[SappySE107]

Id guess injectors as well, or the FPR. Could even be the O2 sensor, so if you haven't done a tune up lately, wires, plugs, O2, check air filter, fuel filter....definetly start there. If those are all less than 30k, then its either an injector or possibly bad gap on the plugs. The coil packs would be doing it all the time I would assume, or more so when hot, and 1 and 4 would be getting the same issues.

[DEI37]

Yeah, that makes sense, sappy. The O2 is original...145,000 miles, plugs are about 40,000 miles, but platinum. I pulled cylinders 2, 4, & 6, and they seemed just fine. Air filter is six months, and fuel filter I never could get off. Tried like a son of a bitch, but it's still on there. At 145,000 miles. Hadn't thought of that. When I pull the #1 plug, I'll take a picture of it, and get a compression reading on that cylinder. I don't want to, because I'm scared of what I might find.

BTW, just a little FYI, the fuel pressure is in spec, if that means anything.

[SappySE107]

The pressure may be up but the flow could be lacking. With that many miles, the fuel filter and o2 sensor are definetly not in good shape. It could be the O2 alone causing fueling issues since they send incorrect readings and slow way down as they age. 60k is the max I would run one, and 30k for peak efficiency.