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#141916 - 08/10/07 02:46 PM P0300 misfire problem!
Emilee Offline
Junior Member
Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
I have a 99 grand prix GTP. I have a P0300 code. (Random multiple cylinder misfire) This code has been coming on maybe once every couple of months. I just kept clearing it because it barely misfired and didn't cause a problem. A couple days ago I was getting on the gas pretty good and then the P0300 code came back. Now while driving normally the car runs fine, but under a load or at WOT the car mifires badly. My coils are new, my plugs are new and my wires are new. None of the wires are burned either. I checked my fuel pressure and that is fine as well. I tried a new ignition module and that isn't it either. Its starting to mis when I start it up and then a little bit at an idle. Any help would be GREATLY greatly appreciated. smile Thanks,
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#141917 - 08/10/07 02:48 PM Re: P0300 misfire problem!
Chunkee Offline
Member
Registered: 04/21/06
Posts: 950
Loc: Charlotte, NC
I had this exact issue last year except mine was the #6 plug code everytime.

Turned out the porcilin on my new iridium plug was cracked right out of the box...I can't tell you the frustration I went through trying to track down the cause..
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#141918 - 08/10/07 02:51 PM Re: P0300 misfire problem!
Emilee Offline
Junior Member
Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
hmmmm... so no P0300 code right? How did you figure out that it was exactly that cylinder? Or that problem.... ITs killing me over here.
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#141919 - 08/10/07 08:43 PM Re: P0300 misfire problem!
Stauffie'sGTP Offline
Member
Registered: 03/30/07
Posts: 272
Loc: Illionis
My car was doing that EXACT same thing...i put new plugs and wires...didn't do it...cleaned my MAF and it has been running strong ever since with no problems...i'd suggest tryin that...get a can of MAF sensor cleaner for like 7 bucks at a parts store...you hafta get "tamper-proof" torx bits...25 size maybe? and just clean it real well..if it works but you keep having to clean it...might be time for a new MAF...good luck...

~Stauffie
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#141920 - 08/10/07 09:53 PM Re: P0300 misfire problem!
ordonez1307 Offline
Member
Registered: 04/18/05
Posts: 8901
Loc: Bradenton, FL
check your plugs first.
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Corey Smith
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#141921 - 08/11/07 02:45 AM Re: P0300 misfire problem!
drummerboy1307 Offline
Member
Registered: 04/30/06
Posts: 3201
Loc: Groton, CT
I would say MAF as well if it's acting up at WOT only. Give it a good cleaning, if that doesn't work, try picking up a used replacement one from Ed Morad.

gtped@msn.com
_________________________

'97 SE with alot of mods
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#141922 - 08/12/07 02:48 AM Re: P0300 misfire problem!
ILGTP Offline
Member
Registered: 07/15/07
Posts: 65
Loc: Montgomery, Il
U&LIM gaskets no doubt
_________________________
1999 Pontiac Grand Prix GTP - 3.2 S/C pulley, DHP v1.0, Short Ram, 180 T-stat, 2.5 Cat back, PEM's, U-bend delete, Res. delete, Autolite 104's, Sprint Springs, RAT swaybars, GMPP trailing arms, GMPP Strut Tower Brace, Debadged, Powdercoated black torquestars, SD Hood.



www.thechicagogarage.org
www.ilgpc.com
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#141923 - 08/12/07 10:52 AM Re: P0300 misfire problem!
Emilee Offline
Junior Member
Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
well see its been doing that ever since I bought the car on and off but not as severe. I put an SS intercooler and a machined lower intake on in december and of course all new gaskets.... so I really don't think it could be that cause the problem is still here.
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#141924 - 08/12/07 11:00 AM Re: P0300 misfire problem!
Emilee Offline
Junior Member
Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
Oh... does anyone know the proper procedure to clean the MAF? I want to be careful and do it right... esp. since that might not be the problem. smile lol
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#141925 - 08/12/07 11:24 AM Re: P0300 misfire problem!
Blackarrow98GP Offline
Member
Registered: 06/29/06
Posts: 3616
Loc: CT, U.S.A
Here's a pic of the sensor: MAF Sensor Remove the screws, lift it out, spray it, let dry, re-install. smile
Here's the stuff you should use: MAF Cleaner
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#141926 - 08/12/07 05:05 PM Re: P0300 misfire problem!
Emilee Offline
Junior Member
Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
thanks guys... ok tried it. Def. not the MAF... I did notice this time though that it only misfires when I make boost. Even if its only 1 lb. Does that narrow it down anymore???
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#141927 - 08/12/07 05:29 PM Re: P0300 misfire problem!
ordonez1307 Offline
Member
Registered: 04/18/05
Posts: 8901
Loc: Bradenton, FL
Quote:
Originally posted by ILGTP:
U&LIM gaskets no doubt
are you serious?
_________________________
Corey Smith
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#141928 - 08/12/07 07:14 PM Re: P0300 misfire problem!
drummerboy1307 Offline
Member
Registered: 04/30/06
Posts: 3201
Loc: Groton, CT
Do you have a Powrtuner or access to a scan tool? If so, you could see which cylinders the misfires are highest.

Maybe your motor has an aftermarket cam in it that a previous owner put it, and you never knew wink
_________________________

'97 SE with alot of mods
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#141929 - 08/12/07 07:59 PM Re: P0300 misfire problem!
ILGTP Offline
Member
Registered: 07/15/07
Posts: 65
Loc: Montgomery, Il
yes im serious. ive had a few cars that i worked on come to me with multiple misfire code on and it always turned out to be the gaskets.
_________________________
1999 Pontiac Grand Prix GTP - 3.2 S/C pulley, DHP v1.0, Short Ram, 180 T-stat, 2.5 Cat back, PEM's, U-bend delete, Res. delete, Autolite 104's, Sprint Springs, RAT swaybars, GMPP trailing arms, GMPP Strut Tower Brace, Debadged, Powdercoated black torquestars, SD Hood.



www.thechicagogarage.org
www.ilgpc.com
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#141930 - 08/14/07 08:35 AM Re: P0300 misfire problem!
4drgt Offline
Member
Registered: 01/08/07
Posts: 6025
Loc: Des Moines ,Iowa
not to thread jack ... but since people were talken about a MAF ... could that cause why my car hesatates sometimes mainly when i start it up ... i am thinking it could be the maf because i have herd people saying that sometimes with an k&n filter sometimes the oil gets on the maf and messes everything up ... just tryen to fig out the problem
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