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The great misfire mystery

Old 12-08-2005, 04:55 PM
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Re: The great misfire mystery

My 99 Firebird has the old cast manifolds. I may start to look for a set of tubular manifolds. I had a good running car until I found out my coil packs screws had loosened over time, after I tightened them, I had all kinds of power now the contact touched well and the misfire went away.-Tim

Last edited by PaganEgyptian; 12-08-2005 at 05:02 PM.
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Old 12-14-2005, 11:52 AM
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Re: The great misfire mystery

Hey Gig. I was having the same problem after making a tune up to my car.
Wires, Plugs, filters were changed You know, the usual.
The misfire occured, then the coils were changed too and the problem was still there.
Untill I joind this page and found out what You suggested, I found a cooked wire on cylinder 6.
So after replacing it the car runs much better.

Thanks for the advice.

Daniel Chairez
Tijuana Mexico.
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Old 01-08-2006, 12:11 PM
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Re: The great misfire mystery

my 98 3.8 had a po420 and p0300 and it would miss whenever i got on it. i changed the plugs, fuel filter, and even went as far as changing the cattalyc converter( which got rid of my p0420) the p300 has not returned but still misses whenever i get on it real hard. when i changed my plugs i saw the wires looked like they were in flawless condition. does this sound like the problem. i guess ill change the wires today.
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Old 01-21-2006, 05:18 PM
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Re: The great misfire mystery

well changed the wires and nothing changed but while i had everything apart i did resistance checks on my ignition coils and found that the middle ignintion coil was completly open no continuity at all. changed that ignition coil and now it runs like a champ!!!
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Old 03-25-2006, 04:53 AM
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Re: The great misfire mystery

it read 0 ohms of resistance? I checked the primary and secondary terminals of all my coils... they all read good (low resistance)
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Old 03-31-2006, 03:12 PM
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Re: The great misfire mystery

I've changed wires, plugs, sparks, coils, ICM still getting p0300 "General Misfire" so I'm thinking its clogged injectors?
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Old 03-31-2006, 03:14 PM
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Re: The great misfire mystery

Originally Posted by jonathan_abilene
I've changed wires, plugs, sparks, coils, ICM still getting p0300 "General Misfire" so I'm thinking its clogged injectors?
check the fuel lifter, accualy replace if it hasn't been done its only 11 bucks and take about 15-30 minutes to change......

then if that dont help look into the injecotors and fuel pump
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Old 04-01-2006, 05:23 AM
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Re: The great misfire mystery

yes, its a new fuel filter
so its either clogged injectors or bad fuel pump @ 38k miles

I wonder if changing my "Injector Flow Rate vs KPA" to 21.99 lbs across the board would cause this misfire?
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Old 04-01-2006, 10:40 AM
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Re: The great misfire mystery

Originally Posted by jonathan_abilene
yes, its a new fuel filter
so its either clogged injectors or bad fuel pump @ 38k miles

I wonder if changing my "Injector Flow Rate vs KPA" to 21.99 lbs across the board would cause this misfire?
chang e it back and see what it does
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Old 04-03-2006, 04:11 AM
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Re: The great misfire mystery

i changed it back to stock so it definately isnt the tune.
its obviously clogged injectors @ 38k miles
I'm going to do a seafoaming, maybe rip the suckers off
and put them in a cleaning agent-solution, then hook each of them
up to a 12v dc
battery(to open it up and let the cleaning agent in)

Last edited by jonathan_abilene; 04-03-2006 at 04:13 AM.
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Old 04-04-2006, 06:08 PM
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Re: The great misfire mystery

think I can just do a fuel pressure check to see if the fuel pump is giving enough pressure? duh Obviously
Its just weird that the fuel pump would act up (showing signs that its going out) without completely going dead.
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Old 04-22-2006, 02:28 AM
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Red face Re: The great misfire mystery

Hello,
I have a p3### misfire code for the number 3 cyl. on a 96 camaro 3800 the SES light is on and blinks, i know this means i can damage the cat so i need help asap.

I changed plugs,wires,coils ECT to no avail my gap is set right and wires are clear of manafold. i am at a loss. the car runs verry ritch, i can smell raw gas coming from the exhaust. so im guessing the fuel filter/pump is ok. it also has starting problems, sometimes takes 3 tries to start. I want to fix this ASAP as i just bought the car and would like it to run right.

Also after changed all the parts the miss got dramaticly better but its still there, i dumped some injector cleaner in it and its helped some but not alot.

PLEASE HELP!!

Don
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Old 04-24-2006, 04:57 AM
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Re: The great misfire mystery

i heard its also bad to run on a constant misfire.
what about seafoam in the gas tank, couldnt hurt?
cylinder 3 is p0303
have you changed the ICM recently?
When cars run lean misfires show up alot more.
I would think that running rich would cover it up?
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Old 04-24-2006, 05:59 AM
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Re: The great misfire mystery

what kind of damage can be caused if the misfire is left untreated
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Old 04-27-2006, 11:03 PM
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Re: The great misfire mystery

ICM? sorry man but could you plz tell me what that is the ICM is ?? Ignition Control Mod? if its under the coilpacks it tests out ok via autozone.

I did a compresion check and i have 180# on number 3 . I did have a cloged cat tho, the prev owner let the wires ground out on manafolds and let raw gas into the cat. i have a pipe in there now and i have alot more power now but still have the number 3 missfire, im also worried abought the o2 sensor behind the cat. i heard i can buy a o2 mask for it.

meanwile i still have the damn missfire. p0303 cyl #3 missfire not the p0300 random missfire. im thinkin cloged injector? plz advice guys. at 2,000 rpm it goes away, and its getting spark?!?

Thx Don

p.s. Wish u could of seen what came out of the cat, ***** of melted crap, and see the diffrence in power! i owned a 3800 firebird and i know it would spin the tries off the line, and well with a miss, that isnt gonna happen and thx for the replys

Last edited by Don350k; 04-27-2006 at 11:06 PM.
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