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misfire??

NewBoost1997

NewBoost1997

New member
Hey. So i have checked and fixed vacuum lines, and I've done new injectors. AND i made sure my ignition was working right....and i still get a slight "misfire" at idle. Like it makes a very very very faint pop or back fire sound in the exhaust every 2 seconds or so? maybe? Idk what it is, and its annoying...

any ideas?
 


Dirty combustion chambers? What kind of plugs are you running? Could run some seafoam through it and see if it clears it up.

Other than that it may just be normal. These motors always have a strange sound to them running and I've heard mine pop like that and it runs just fine. If the misfire isn't causing a vibration from the motor (ie- it idles/runs smooth) then I would try the above seafoam and call it good.
 
Are you getting any codes? No, that is not normal. Haha. Try new plugs and make sure your wires are good and go from there.
 
So i have check my coil packs, plugs, wires, vacuum lines, compression tests and everything is good. the only thing my car was throwing for codes was a MAP/BARO sensor that I just replaced so thats fixed, and it keeps throwing PO301 (Cyl. 1 misfire) if I let it idle for more than ~2 min without giving any rev or driving. I've been chasing this down for a few weeks now and I'm starting to get pissed. Im going to try running seafoam to see if i might have a sticky lifter, then change plugs and wires again....because i didnt do them, the owner apparently did before I bought it....look fine, but I might just do em.
 
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I would to...swap those coils.

Uhhh, also...remove the coils and have the ICM tested if you haven't done that yet.
 


Still no luck. My supercharger went bad so I had to replace that and I thought maybe it could be the gasket that is between intake and supercharger that was bad and causing misfire. Nope still there. I have autolites 104 gapped to .053" in and new wires. New O2 sensor in my rear header (cat is gone due to headers). Every mod for the 3.4 pulley setup. Sometimes it idles ok sometimes not. What happens is it'll drive perfect. But when stopped (say at a stop light) the rough idle/misfire starts about 3-5 seconds after stop moving. Sometimes on my volt gauge there is a 2 volt drop whn it misfires. But then when it continues to misfire after that, the voltages stay ~14. I'm worried it's a head gasket or maybe a ever so slightly bent valve. But wouldn't it run like crap when driving too?
 
I have an aftermarket intake, It rests right above the PCM. My intake over time was rubbing against some wires on my PCM and started giving my problems with Cylinder #1. Fixed those wires and added another rubber hose over them to help with anymore rubbing. Running good since.
 
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