PLEASE HELP!!! Misfire 2005 engine swap plus p0300 code

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aminoacid

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Hi guys i'm new here. I have been lurking forums for a solution to this problem i'm having with my cavalier. I bought it for a good deal and ended up needing an engine (water mixing with oil, did head gaskets and that didnt fix it, mechanic said swap the engine those head gaskets are hard to fix the problem on those ecotech engines)

Anyways prior to the engine swap it wouldn't run right, converter getting red hot....etc.
swapped engine with 70k engine, gutted the converter. It'll start and run sometimes but will have a bad misfire, p0300 sometimes feels only 2 cylinders are firing. i noticed it happening more after a spin around the block or after it warms up a bit, but it also does it when its cold but not as bad.

I changed igintion module, coil packs, crank sensor and also grounded the ignition module thinking it might be a ground to it. Is there some kind prgramming needed like a relearn to the cranksensor - pcm?

anybody have experience or know what i should do next? replace pcm? if thats the case does it also need dealer programming?

I am in desperate need to get this car back going. so much for a good deal
 
anybody have some advice besides lighting it up in flames to a crisp?
 
have you checked for a vacuum leak? have you googled "OBDII code PO300" for suggestions?
 
zora said:
have you checked for a vacuum leak? have you googled "OBDII code PO300" for suggestions?
Click to expand...


i did check for vacuum leaks and found nothing, spraying carb cleaner on intake didn't reveal any change either.
 
was the coil pack new? How many miles on new motor? You can try a compression test. What about the maf (mass air flow sensor) chevys are known for them.They can give off a misfire code as well good luck.
 
the coil packs are not new. I tried another used coil pack. The ignition module was replaced with a new one-- no change.

converter was gutted cuz getting too hot, i will replace it when i fix the misfire.

Still not fixed. I dont know where else to look
 
since the convertor was running hot you must have had a rich mixture. Did you test the fuel injectors? Did you test/check the pressure regulator?
 
zora said:
since the convertor was running hot you must have had a rich mixture. Did you test the fuel injectors? Did you test/check the pressure regulator?
Click to expand...


The car does this after running for a while like at a stop light it will start to stumble and sputter like its running on 2 cylinders, barely runs.

i tried unplugging the injectors while its running good and it''ll misfire with each injector. fuel pressure test after running the car for a while is about 62psi.

talk to the dealer and the service managers are clueless, giving all kinds of information. one says doesn't need a case learn if its running, one says it might run good, run lousy from case learn. gonna charge me 95 diagnostic and 95 to do case learn.

My question still stands whether I need a case learn from the dealer or not with a used engine replacement.
 
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