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P0300 random misfire after intake gasket job??


douellette

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alright so i just finished doing the intake on the 96 monte carlo 3100. Started the car up and if i let it idle, it sounds like it has a race cam in it. but if i hold the throttle a little bit it runs smoothly.

 

i put my scan tool on it, and all it says is p0300 random misfire.

 

i squirted soapy water around anywhere there could be a vacuum leak and i didnt see any bubbles.

 

the only thing i saw when reassembling it was that one of the plug wire boots (the end that goes on the plug) had a tear in it, about 2 cm long. i didnt think it would matter, but maybe the spark is arching out? I Ohm'd all the wires and they were all in spec tho.

 

What do you guys think??

 

Also, i replaced all the spark plugs and yes they are all gapped correctly.

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i swapped a known good plug wire from my cutlass temporarily to this car on the plug wire with the cracked boot.

 

idont know if it was my imagination or not, but it seemed like ran a little bit better.

 

the way it idles is like a super fast surging type of thing, "rm rm rm rm rm."

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Spray ether instead of soapy water around the intake. The ether will cause the engine to race if you do have a leak.

 

well theres no reason it should be leaking. i torqued everything down. Theres no way im tearing that all apart again. Took me about 2ish whole days to do the repair.

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Maybe there is a vacuum line disconnected somewhere?

 

not that i could see. but i broke the hose for the PCV valve. the small hose that goes to the back of the engine where it connects into the top of the throttle body. i thought i resealed it though, i put some silicone around it. I was going to get a new one, but i woulda had to wait a day for them to get the part.

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Try the ether idea... You dont have to tear into it, just trace the vacuum lines with it and listen for the idle to change

 

well i dont have just ether, i have carb cleaner tho so ill try that.

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okay well i sprayed it all around the engine, and around the pcv harness that i thought i repaired and it made the engine run smoother. so im assuming thats where the vacuum leak is. I ordered a new "harness" from advance, will be installing it tomorrow.

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