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Help! 2004 Cavalier 2.2 OHC Ecotec staggers on acceleration but only when this happens

I have a 2004 Chev Cavalier with a 2.2. Ecotec OHC. Lately the car has started to stagger on acceleration. Particularly when going up hill. The weird thing is, it only does it after it’s been running for 10 or 15 minutes. Up until that time it runs smoothly. But when it happens it feels like the engine bucks. Or hiccups. If I stomp on the gas the car will either stall or kick in and overcome this. When I’m driving down the road at a steady speed, or when I’m sitting still the engine will buck in the same fashion. Not steadily–intermittently. Once or twice every fifteen seconds. But it’s getting progressively worse. Now if I launch out of an intersection the car might even stall. When this happens I just turn the key and she fires right up again as if nothing happened. No “Check Engine Light” or trouble codes showing up in my Scangauge. I replaced the fuel filter just as a preliminary measure but that didn’t solve the problem. I had the fuel pump replaced a few months ago as well but that ws before this problem occurred. No other parts or pieces replaced. Fuel pressure regulator? Spark plugs? Injectors? Deep, mysterious (and costly) part that no one would even think about? Any help would be much appreciated!!

How many miles on this car?

Does “Spark plugs?” mean you haven’t replaced them yet? If it runs well other than this stumble, I would suspect they’re not the problem, but they’re a relatively cheap, and easy home mechanic job.

Have you tried having the throttle body cleaned (or doing it yourself)? It’s a simple operation, if you can remove some bolts, and disconnect a wiring connector (maybe a couple coolant lines).

Just a couple thoughts. I’m sure there will be more.

Thank you for the reply, Chaissos. I have 150,000 on the car. The weird thing is, it seems to only happen after the car has warmed up. And when i’m going up hill–that’s when it gets annoying. I can get to the throttle body pretty easily. Think that’s a good place to start? The plugs are probably overdue, too. What about the fuel pressure regulator?

I wouldn’t think the pressure would be a problem, since it runs OK before it gets warm. There should be a temperature sensor that may cause this. If it’s not seeing the engine as warmed up, it’ll be using too much fuel, due to it thinking the car is still cold (like running the choke slightly on an older motor). Pull the plugs (and have replacements and anti-sieze ready). If they’re all black and fuel drenched then you know it’s using too much fuel. Use this chart to compare to what you remove.

I will do this–but it might be a day or two before I can get a break in the schedule. The temperature sensor sounds intriguing. That would make sense. I’ll be back soon once i’ve pulled one of the plugs.

Ummmmm…if the plugs are original than yes, the plugs are overdue. Way, way overdue. And they may be the source of your problem.

Plugs initiate combustion by a high voltage electrical “spike” arcing across two seperated electrodes. As the engine runs, material is vaporized by the high heat created by the electrical arc. The electrodes erode away over time until the gap becomes too great for the voltage to reliably jump the gap. Symptoms will be exactly as you describe.

Even irridium plugs, plugs with irridium center electrodes (the arc goes from the center to ground…we won’t discuss “wasted spark” ignitions) are required to be replaced at typically no more than 100,000 miles.

Chassos linked to you an excellent chart that you can use to “read” the condition of your plugs. Let us know what they look like when they’re removed.