Random Misfire Code PO300??
12-24-2008, 01:34 PM
#21
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open the hood and start the car in the dark, look for spark occuring outside the plug/wire in little blue flashes. i had that problem and it turned out to be a bad wire that had bad insulation.
12-25-2008, 06:31 PM
#22
I thought about doing that, but did not think it was bad enough to see. So much for me 'thinking'. I decided to try it tonight. I can see the flashes at idle in several wires, not all. They are confined to the plug boot, but I am sure that under load I am loosing spark. I have new stock wires to replace the MSDs and then I'll know for sure. Thanks for the idea again.
01-02-2009, 11:45 AM
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replaced my wires Hey guys i just installed my Jegs 8.5 and they are a perfect fit. I found out that i had 3 MELTED wires to my Edelbrock headers and about 4 or 5 spark plugs were loose. So took all of em out cleaned, gaped and installed them along with the wires. Now the miss is smaller than what it was , my car doesnt shake when i put it in drive. Now my MPG whent form 13 to 17.5 on the freeway . I reset the pcm and the random missfire code came on again. What is you guys MPG and MILES TO A TANK just to compare were im at. Next thing is a New Delphi cap and rotor or MSD what should i go with???
01-05-2009, 08:23 PM
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I'm hating this...what's next? Hi everyone...I'm new and already fed up with my bird, hehe. I've been having a lot of problems with misfiring since I bought her in April last year. Three days after I bought her, she was misfiring, my service engine light was blinking during acceleration. I was dumb enough that I honestly didn't know what a darn misfire was. I'm learning a lot however. I took the car in to the dealership where I bought it and they ran a test, said one of the coils was burnt out, and they changed it out and the spark plugs as well as a courtesy. 50 miles down the road, and the light comes on again. No misfire this time, just the solid light. I called around, did some reading and realized it could be my catalytic converter. Got another diagnostics run, and it was. Luckily, my car was still under the 80K mile mark, so I got my cat replaced for free at the Pontiac dealership. The guy told me to drive easy to let it "burn in" and so I did. Well, to this day, it still sounds like someone's rattling rocks around in a tin can when the engine is revved up. I don't know why, but I still have another warranty on the new cat if for some reason it was installed wrong. Either way (I'm blabbing like a typical woman)...recently, I had a problem with the misfiring again, it sounds good in park at idle, but as soon as I put it into any other gear it feels like the whole car drops two inches lower and shakes pretty heavily, like it's preparing to throw up. At this point, the light starts flashing, and while accelerating no matter the rpms, it's flashing. Sometimes it'll level out while driving between 55 and 60 mph and the light will be only solid. But eventually flashes again when I slow down or accelerate again. Now, a few weeks ago, I changed out my sparkplug wires myself under supervision, and as soon as I did, it ran great for about a week. Then it started misfiring again. So I changed my sparkplugs. Got Bosch Platinum +2...the double pronged plugs? and changed those out. Had someone check to make sure I did it right. And the problem has only gotten worse. What next guys? The coils? Or could it be the fuel injection or cat again? I'm so lost and so new to this. All help appreciated.
01-06-2009, 04:47 PM
#28
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Here's my input and some questions.
What kind of engine to you have (V-6 or V-8) and what year is the Bird?
Flashing check engine light means multiple mis-fires. Serious malfunction.
Just because a coil/wire/plug problem has been fixed doesn't mean it didn't come back or is still the same problem with a different coil/wire/plug.
Wait until dark, start the car and look for sparking/arcing around the area of the coils and wires. If you see little flashes of light, that's where to look for the problem.
Bosch plugs do not work well on these cars. Multi prong stuff is just marketing.
Stay here on LS1tech. It will get figured out.
What kind of engine to you have (V-6 or V-8) and what year is the Bird?
Flashing check engine light means multiple mis-fires. Serious malfunction.
Just because a coil/wire/plug problem has been fixed doesn't mean it didn't come back or is still the same problem with a different coil/wire/plug.
Wait until dark, start the car and look for sparking/arcing around the area of the coils and wires. If you see little flashes of light, that's where to look for the problem.
Bosch plugs do not work well on these cars. Multi prong stuff is just marketing.
Stay here on LS1tech. It will get figured out.
01-06-2009, 08:45 PM
#29
im fighting the same problem but i have a p0121 tps code with it. I've checked and changed o2 sensors, plugs ngktr6, wires msd (exhaust gaskets that helped with the jerking) checked for vacuum leaks with carb cleaner. cleaned the maf sensor with maf cleaner put lucas injector cleaner in gas. checked rockers, springs, pushrods for damage. the light doesnt flash and sometimes even goes away but it sucks gas on down fast proly cause the tables it runs when you have a trouble code. things i havent checked yet are crank position sensor, and to see if the missfire table in the tune is set to sensitive. also today a guy at work had the same code (wierd) he has a type r but im going to help him find the problem it may help me find mine. I'll keep yall posted with what i find.
and if anyone has any other ideas let me know this is my dd
and if anyone has any other ideas let me know this is my dd
01-07-2009, 12:11 AM
#30
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optispark Hey guys quick question. Thinking about replacing my optispark. The person i bought the trans am from said he replaced it, but i dont know if he did the whole distributor or just the cap and rotor. It looks like he did, i can see the fresh gasket maker on the water pump??
1. Do you guys just get the CAP AND ROTOR or the whole distributor?
2. If cap and rotor should i just go oem( Delphi/Ac Delco) cap and rotor or an MSD cap and rotor???
1. Do you guys just get the CAP AND ROTOR or the whole distributor?
2. If cap and rotor should i just go oem( Delphi/Ac Delco) cap and rotor or an MSD cap and rotor???
01-07-2009, 07:51 AM
#31
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This is only a suggestion, take it for what it's worth........
My daily driver is an 02 Avalanche, I had been getting the same code on and off...I tried all the basic stuff up to and icluding top end cleaner thinking it was carbon.
In the end it turned out I had an intake manifold leak throwing the misfire code.........just something else to take a look at if you['re beating your head off the wall.
My daily driver is an 02 Avalanche, I had been getting the same code on and off...I tried all the basic stuff up to and icluding top end cleaner thinking it was carbon.
In the end it turned out I had an intake manifold leak throwing the misfire code.........just something else to take a look at if you['re beating your head off the wall.
01-07-2009, 10:57 AM
#32
hey goldbird did you go and see if it was the same code that you had before? how many miles on your v6? I seen on other threads that you have been chasing this problem for a min while i was searching for things to look at
01-07-2009, 06:40 PM
#33
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I checked for sparks last night and there were none. But i did see some OIL leaking from the bottom of the throttle body. What gasket is right under the throttle body? Intake manifold?
01-08-2009, 05:45 PM
#34
when i changed out my header gaskets (oem manifold gaskets) the missfire didnt show up for a few days and i didnt hear any noises. now the p0300 comes on faster and i hear that noise again but its getting louder. im getting ready to go and see if the header bolts are tight and also check spark plugs. oh and when i checked the trouble codes i didnt have the p0121 (tps sensor) so i guess cleaning that sensor with carb cleaner did some good. ill post what i find. any update on anyone else?
01-10-2009, 11:35 PM
#36
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missfire Well i just got home and before i turned the car off i decided to unplugg one injector at a time to see if it makes any difference. So it did, i unplugged #4 and nothing changed in the idle while all the rest of the cylinders did have a change when unplugged. So tomorrow ill check for spark and ill let you guys know whats up...
02-22-2010, 05:43 PM
#38
Found it...My cat was hitting the undercarriage of my car enough for the knock sensor to pick it up and pull the timing. It was so intermittent no one could get it to happen till a few weeks ago.
02-27-2010, 06:12 AM
#40
1-1/2 years lol! Drove me nuts at times and I considered getting rid of the car. But I was stubborn and wanted to find it. Just hope this helps someone else who may be in the same situation.
