iAmLothario

I have a '97 V6 Firebird that threw a P0300 code "Engine Misfire on Random/Multiple Cylinders". The car stutters and stalls, and the other day the "Check Engine Light" not only came on, but it started flashing. I have replaced the fuel filter and a coil pack that was arching (I saw sparks coming off of it). None of my spark plug wires are melted (as seen on a previous post), and I am not due for a tune-up yet. Any suggestions to what the problem might be/how to fix it would be greatly appreciated.

ImportKILLER

How do you figure you are not due for a tune-up. You can't base that solely on mileage or age but you need to base that on the performance.

It could be anything from plugs to wires to packs to a lot of other stuff.

Cobalt

import,

if you do your homework, you will find that a P0300 code is a random misfire, meaning it jumps from cylinder to cylinder.

random misfires arent generally due to faulty plugs, wires, coils, injectors, faulty rings, or anything else that would usually "pin" the misfire to a certain cylinder.

from my understanding, random misfires occur because of vacuum leaks, or a severly incorrect a/f ratio ( fuel filter, pump, regulator, etc).

so, if anyone else has any first hand experience in this. please chime in. this guy sounds like a weiner, he probably needs the help. ( j/k john....by the way, thats a gay handle to have on a message board )

Rich97 W68

I have burned up plug wire #3 and plug #3 three times now.

Instead of PO303, I get PO300. The other wires check ok, as well as the plugs and coil packs.

PO300 could be because of wire(s), plug(s), coil pack(s), fuel pump going bad, etc...

Check the wires and plugs first. If they're okay, go on from there.

R

kahouna23

Rich,
I've had the same problem with my 99'. #3 plug and wire are the cause of my problems every time. I've had to take my car in going on 5 times for this very same problem. Is there some sort of service bulletin, or even a recall on how the #3 wire is routed. It seems that it's routed so close to the manifold that it's melting from the heat causing it to arc. Just to let you know, you're not the only one...not that I'm saying that's a good thing, but you'd think Chevy would do something about it because it seems to be a VERY common problem. Please let me know if you have any info on this subject because I'd like to have some "ammo" when I go to the service department for the 5th time on Tuesday.


Thanks ahead of time.

Rich97 W68

Honestly, the only TSB I know of is the one about replacing OEM wires within 70K miles for free because of a problem with the wires.

That might work.

#3 is always my culprit. Without fail that's the one that craps out.

My dealership's suggestions? None.

Everyone else's? Buy headers.

Doh!

R

ImportKILLER

Thank you.

I do have first hand experiance with this situation. First time, it was my plug wires going south. Random misfire code. Second time, it was a cracked plug. Same code.

As for homework, why should I do homework on what a p0300 is when he already said what it was in his original post?

Nice way of introducing yourself to the board.

As for the TSB, just tell them about the wire recall/replacement. When I went, they didn't tell me and I had to pay up front. Later on, I found out and went back to them. Had to wait 2 months to get my $$$ back too...luckily I went to a different dealer who was honest enough to give me a copy of the recall.

Cobalt

yada yada. maybe im wrong. it wont be the first time. or will it??

sorry import. your answer seemed a little vague. i just dont see why the pcm would throw a random code when one (or more) cylinders misfire repeatedly.

well heres the deal, as john said earlier, the fuel filter was replaced. check the pressure today and it measured around 45 psi. lost about 2.5 psi over 10 minutes. so no indication of fuel leaks. checked for vacuum leaks, none found. sprayed wd 40 around intake manifold and vac. lines. nothing. changed the coil that was arcing (the one closest to the front of the car...not sure which that is).

so....its not a fuel or vacuum leak issue. and probably not a coil pack issue. or is it? what next? new plugs and wires? here is the million dollar question......can plug wires be burnt and work improperly without any visible charring or signs of burning?????

also, one last thing. i read about someone throwing the same code and changing the camshaft position sensor. could that work? sorry for the long post and many questions.

judd

iAmLothario

Ok so there is a very good chance that its my no. 3 spark plug wire, or maybe a position sensor. It was mentioned that my cat might be clogged...does that mean I have to buy another one or is there a more creative/performance solution? Also, how do I know if it is clogged or not?

Thank you all for replying so far...it has been very helpful.

Rich97 W68

Yeah...I got shafted by a dealership that made me pay, too. Refused to reimburse me when I brought the TSB to them. Live and learn...never go back again, and tell ALL my friends, family, and everyone here about it and other problems with them everytime I get a chance.


(Boycott Jay Pontiac Columbus, Ga and Ga Square Auto in Athens).


Clogged cat will not *usually* cause a PO300. If it were a crank sensor, you should be, though not necessarily 100%, be throwing another code about the sensor itself.

PO300:

Plug, wire, coil pack (easy to take off and test) are the MAIN culprits.

Plug wires CAN be burnt with NO external sign of wear/burning. Last time, or maybe the time before (?) #3 was fine on the outside, but burnt to high Hell inside.

You can test the wires, coils, and check all plugs...those are Step1.

With no other codes, I'd almost assure you it's one of those three things.

Check them out and let us know what you find.

R

ImportKILLER

Rich, how is it that they didn't want to pay you? If you paid for the wires that should have been covered, they should reimburse you, especially if it was within the warranty period/mileage. I had to write in to GM to get my check. If you still have your paperwork of when the repair was done and if it was within the range, you should still be able to get your $$$ back. The dealership tried to keep my $$$ too so I had to leapfrog them and go straight to GM.

The three times I've had a flashing SES light with those symptoms it was:

1st: Burned stock plug wires - usual crap stock wires
2nd: #3 Spark Plug Cracked - overtightened
3rd: Burned replacement wires - again, crap stock wires.

I've got money on wires and/or plugs...

gig

Yo--

I have been chasing the same problem on my 97 3.8 Firebird automatic. Recently I got a P0300, P0306 error when the car was stuttering really bad, making it undriveable. I replaced the ignition module and 3 coils, the stuttering went away. I still have an occasional miss in overdrive with the torque converter locked up, but this was from before anyway. Here's what I troubleshooted for the occasional misfire:

1) I have replaced the camshaft position sensor, but the occasional miss is still there. Replacing the ignition module/coils helped a lot--the miss doesn't happen all to often now. My plugs have 20,000 miles on them, so they're do for a change anytime now.

2) One thing to consider is that our engines run hot. Due to the design of the car and the way the engine is tucked in, the underhood temperature is very hot. Hotter coils, wires, etc., will take more energy to fire the plugs.

3) The design of the DIS means the plugs fire twices as often. They will thus wear more often too. While platinum plugs do last longer, they have more resistance. The dealer installed new AC Delco platinums (what our cars came with) when my car misfired; they ran fine for 10,000 miles, then misfires began after. My Bosch platinum plugs misfired right after I installed them. The Autolite Pro Platinums ran fine for 7,000 miles, then misfired after. My car runs best with the Autolite Racing plugs. The only problem is that they last around 25,000 miles or so.

4) The factory wires were recalled, so GM knows they don't last. Basically, the heat in the engine compartment will cause these cheap wires to break down. If your wires are bad, there is a chance they ignition module could get damaged. I know a lot of people like Taylor wires, but I've had great luck with MSD 8.5mm Superconductor wires. They're more expensive than Taylors, but in my opinion worth the price.

5) I also changed the fuel injector on that cylinder (#6), but the occasional misfire was still there.

I would first change your plugs, wires, fuel filter, PCV valve. Use high quality parts, too. Try switching the coils to see if you still get the misfire since a coil may be damaged. Look at the companion cylinder that fires along with the culprit cylinder. Hope this helps.

Rich97 W68

Great post, gig!

I, too, have an occasional misfire. Logging on autotap I've noticed that in 2nd-4th gears around 3500-4200 I have this weird hesitation, coutable (though not major) misfires, and knock retard. This is either at WOT or part throttle.

If the knock retard is not present, the hesitation almost goes away. However, I haev logged many runs where KR was 0* throughout the entire run, but misfires pop up around 35-4000 RPMs.

I don't know what on earth this could be caused by. I'm replacing the fuel filter and possibly pump, wires, plugs, and coil packs sometime soon. I'll keep everyone posted on what the results are.

R

Rachel Esteppe

iIs the LCM good? My coil pack was put on too tight and it broke the 2 prongs off inside the coil pack and caused it to misfire. i didn't see the tread was from 2002😂