I have a 07 Chevy Impala SS with Magnaflow exhaust and a K&N air intake. I replaced the spark plugs/wires, #3 Fuel Injector, Intake Manifold, and swopped out both coils (For testing). All the parts are OEM. When I accelerate past 40Mph the car misfires doing a little hesitation or loss of power. When I get to 80Mph its struggles to maintain that speed. I would have to add more gas to maintain that speed or it will lose RPM and power. I got a pressure test done and the pressure is just a little low. I was told to go to the dealer and that want to do another pressure test or cylinder leak test that will cost $300.
The misfire stayed. Basically its like a small rough idle and I'm assuming its missing before acceleration. Maybe some type of slug or carbon build up causing a valve not to properly close.
I used a product call Gunk Engine Flush and I started to feel results instantly. There barley any idle issues but I can hear a whistle sound. I think my misfire could be coming from a vacuum leak. I still have the misfire cylinder 3 but I'm not feeling any performance issues.
^ Basically, usually it accumulates more from low quality gas, whether it be arco, or just winter blend, it adds up. Techron, and other proprietary additives help break it down, but best bet is to run seafoam every few tanks or so.
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