#141916 - 08/10/07 02:46 PM
P0300 misfire problem!
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Junior Member
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Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
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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. Thanks,
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#141917 - 08/10/07 02:48 PM
Re: P0300 misfire problem!
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Member
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Registered: 04/21/06
Posts: 950
Loc: Charlotte, NC
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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!
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Junior Member
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Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
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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!
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Member
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Registered: 03/30/07
Posts: 272
Loc: Illionis
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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!
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Member
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Registered: 04/18/05
Posts: 8901
Loc: Bradenton, FL
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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!
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Member
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Registered: 04/30/06
Posts: 3201
Loc: Groton, CT
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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
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'97 SE with alot of mods
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#141922 - 08/12/07 02:48 AM
Re: P0300 misfire problem!
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Member
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Registered: 07/15/07
Posts: 65
Loc: Montgomery, Il
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U&LIM gaskets no doubt
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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!
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Junior Member
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Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
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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!
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Junior Member
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Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
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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. lol
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#141925 - 08/12/07 11:24 AM
Re: P0300 misfire problem!
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Member
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Registered: 06/29/06
Posts: 3618
Loc: CT, U.S.A
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Here's a pic of the sensor: MAF Sensor Remove the screws, lift it out, spray it, let dry, re-install. Here's the stuff you should use: MAF Cleaner
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#141926 - 08/12/07 05:05 PM
Re: P0300 misfire problem!
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Junior Member
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Registered: 08/09/07
Posts: 10
Loc: Ada, Ohio
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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!
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Member
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Registered: 04/18/05
Posts: 8901
Loc: Bradenton, FL
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Originally posted by ILGTP: U&LIM gaskets no doubt are you serious?
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Corey Smith
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#141928 - 08/12/07 07:14 PM
Re: P0300 misfire problem!
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Member
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Registered: 04/30/06
Posts: 3201
Loc: Groton, CT
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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
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'97 SE with alot of mods
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#141929 - 08/12/07 07:59 PM
Re: P0300 misfire problem!
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Member
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Registered: 07/15/07
Posts: 65
Loc: Montgomery, Il
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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.
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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!
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Member
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Registered: 01/08/07
Posts: 6026
Loc: Des Moines ,Iowa
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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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