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Discussion Starter #1 (Edited)
Hey guys, not really sure where to go with this question as it seems forums relating to the Cavalier and 2.2 Ecotec engine are rather dead, and I'm having an issue.

I picked this 05 Cavalier up a few months ago with a bad engine (2.2 ecotec). I decided I would pull the blown engine out and swap in a 2.2 from a 2003 Grand Am. I successfully completed the swap albeit one issue. The fuel injectors from the 03 Grand Am 2.2 didn't match up to the 05 wiring harness. I tried to take the injectors out of the blown engine but these injectors did not fit into the fuel rail from the Grand Am. I ended up going to the junkyard and buying a fuel rail and injectors from an 04 2.2 and installing those on the 03 engine, and all went well from there. I should note that the engine has an aftermarket intake and header.

Now that the backstory is out of the way, here's the problem. Basically when I'm cruising down the street, in any gear (the car is 5 spd manual), when applying light throttle the car hesitates and studders, like it's having a misfire. This was confirmed when the check engine light came on reading P0300 (Random/multiple cylinder misfire). I also got a CEL for a small evap system leak but I believe that is unrelated to the misfire issue.

To try and fix the issue I first inspected the spark plugs. What I saw was that two of the spark plugs were completely blunt, they hardly had any electrode left on them, while the other two spark plugs appeared to be nearly new. I removed the spark plugs from the 05 engine as they were still in good condition and I put them in the car. Thinking this would fix the issue I took the car for a test drive, but it is still having misfires. I pondered a bad ICM or ignition coil, so I swapped over those parts from the parts on the 05 engine and took the car for another test drive. The problem persists.

My next approach was changing the TPS, finding that the misfires only occur at light throttle and go away with heavier throttle, I thought that the TPS might have a malfunction. Swapped the TPS over from the 05 engine and the problem still failed to go away. My next hunch was that the car had been sitting for months before I bought it, and that meant that it had old gas. I filled the car up with fresh fuel, added some fuel system cleaner, and even changed the fuel filter but the problem still exists.

I'm out of ideas as to what could be causing this problem, and my hope is that somebody here may have any idea what it could possibly be!
 

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Bo Baustin
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Do you think you have 2 bad injectors? Or at least clogged so it's causing a lean condition in those 2 cylinders and misfiring?
 

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Discussion Starter #3 (Edited)
Do you think you have 2 bad injectors? Or at least clogged so it's causing a lean condition in those 2 cylinders and misfiring?
I haven't ruled that out, I just wish there was a way to test the injectors to see if they're flowing properly. As far as a bad injector (or 2) goes, would a fuel system cleaner remedy that?

Edit: Well I performed an impedance test and for what it's worth all injectors came back at 13.5, on a cold engine.

Second edit: Just did a compression test and the car came back 120 across all cylinders, hm.
 

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Bo Baustin
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An impedance test wouldn't show a partially clogged injector. They could still by firing but not moving fuel.

The guy who built that RX-7 with the LS1 in it unclogged his by hooking up a hose and using his mouth to blow cleaner through them while opening and closing the injector with a 9v.
 

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Discussion Starter #8
Alright looks like the next course of action is pulling the injectors and cleaning them. I'm not sure if the Cavalier is capable of showing which cylinder is misfiring, the code it currently reads states Random/ Multiple Cylinder misfire. Haven't made any progress since that compression check as I've been busy with work and school, does anybody know if the symptoms of a failing crank sensor could be my issue or not?
 
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