I Think Solved my intermitant misfire!

carnut726

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This is the wierdest thing i have ever seen for a diagnosis. I have had an intermitant misfire for a while and was never able to trace it. I put in new fuel filter, checked fuel preassure, new spark plugs, new coils, new PA Perf alternator, restored my computer from my sct tune to stock, everything i could think of. While driving it home from work about a week ago i felt the misfire or a small miss in the seat of the pants but no code was coming up. so i turned off the air/radio etc to listen for it. couldnt hear it. said screw it then it happened again a while later. so again i turned off the air/radio etc to listen for it. it was gone, Then the light bulb went on... (i m kinda slow) I drove it with the Air conditionoing on and got the miss, air off no miss. I never drive the car without air because i put it away after summer and drive one of my other trucks for the rest of the year.
Apparently my Air conditioning compressor unit has a lot of drag when on and is slowing the belt/other accessories down so much that its causing a misfire. Since driving it without the Air on i havnt had one Misfire since.

Does this seem possible to anyone? Because its seems to be very cause and effect here!
 

quick01snake

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If you are just feeling a 'hiccup' with the air on it could be that the compressor is putting a sudden load in the engine via the belt when it kicks on. If it is on its way out it might have a high spinning resistance causing a bump you might feel through the drivetrain when the clutch first engages. Dies the ac compressor make any noise while it is on?
 

carnut726

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Yes i think thats it. But sometimes the hiccup is so bad it throws a code. It makes no noise at all.
 

carnut726

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Just for the record mine is also a performane red cobra like yours.... Its the finest of all the colors.
 

Digital

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If you are just feeling a 'hiccup' with the air on it could be that the compressor is putting a sudden load in the engine via the belt when it kicks on. If it is on its way out it might have a high spinning resistance causing a bump you might feel through the drivetrain when the clutch first engages. Dies the ac compressor make any noise while it is on?
^ also if your compressor shaft is gummed up or the pulley is out of whack it could in theory put enough load on the crank to cause engine slow down.
That being said your engine management system should be able to compensate for that without a back fire.
 

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