Went to dyno, got random misfire instead!

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Dec 8, 2005 | 06:25 PM

DRGnFLYZ28

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From: SoFla

Went to dyno, got random misfire instead!

PLEASE help!
Fuggin frustrated!
Went to dyno the Z today and on the way there hit a few WOT runs and all I got was serious misfire. Had the dude there run a diagnostics and all he was able to see was random misfire. Because the code is intermittent, I can't run a DTC diagnostics with my Crane Power Tuner.
Took the car home and checked the plug wires, plugs, all electrical connections, removed MAF, TB, PCV and cleaned, removed Crane tuning and reset the ECM tune to stock. Even reset the ECM. Same symptoms. Rough idle, engine shaking like ****, misfire off-idle and under load. Smooths out at higher revs but give it a little throttle and you get some nasty misfire.

Your thoughts/suggestions are greatly appreciated!

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Dec 8, 2005 | 07:53 PM

crazy camaro

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From: fresno ,ca

i had the same code before and i also run that same tuner and my pcm was bad when that happened best advise is to diconnect the battery and the computer for 15min or so and plug everything back in and see if the tuner will allow you to custom tune or even load stock settings also check the coil wires while unplugged

Dec 8, 2005 | 09:53 PM

shaun

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well i had that problem with my 98 pontiac gtp. i couldet figure it out for nothing.all the wires where new and the plugs. but for some reason it would fry one of the plug wires when i would hit the rev limiter. i went through 3 sets of wires the tinyest crack in the boot or wire will make it run bad.try changing your wires for a fresh set. hope this helps

Dec 9, 2005 | 02:06 AM

ls1birdman

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From: Fontana, C.A

My car is doing the same thing and all I did was change the spark plugs and the o2 sensors and it started doing it and I checked every plug they were all good and took the o2 out put the stock ones back and it was still misfiring on idle.....

Dec 9, 2005 | 05:41 AM

Brent@LPE

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From: Decatur IN.

you could pull the cover and look for a bent pushrod

brent

Dec 9, 2005 | 06:15 PM

DRGnFLYZ28

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From: SoFla

Thanks to all the replies!
I took the car to two dealers and they both couldn't take the car 'till next Wednesday. Wouldn't even run a diagnostics for me at top dollar (dirty bastards

) so during my drive it threw a code that stayed on:

Got home and grabbed the tuner and checked the code.
P0305
Per the Crane Diagnostics reading = "Fuel delivery per cylinder #5 excessive"

Now, the car will sit 'till Sunday at which point I will look at the wire resistance and plug condition. Any suggestions on checking the injector? If it is the injector, I'm installing the 30psi or 36psi I've been wanting.
Wonder if the O2 and cat suffered during this rich condition... you could smell the fuel from the tailpipes.

Any suggestions?

Dec 9, 2005 | 08:03 PM

DRGnFLYZ28

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From: SoFla

Problem Solved!!

Couldn't wait 'till Sunday so I pulled it into the garage, put on the mechanic gloves, pulled the wire and plug and low & behold, the brand new AC Delco Iridium plug had two severe cracks from the tips to the threaded base!!
Swapped out to one of the OEM platinum plugs and problem solved.
AMAZING how a cracked plug can wreak havoc with an engine.

Now to replace the plug and find the time to get it dyno'd!