Misfire with P0300

[Justin.Kirkham]

The other day my 2000 Firebird started up hard and was shaking fairly significantly. It felt like a misfire, and very quickly I got a P0300. I drove the car a short distance, but the misfire remains, though it did resolve for about 10 seconds randomly the other day at idle. Anyway, the misfire is consistent and rhythmic, if that makes sense, and my car now sounds like a helicopter. When I did drive the car around the block, other than being powerless and shaking, it drove as normal. The misfire didn't cause the car to stumble at all, however.

I uploaded a quick movie of the misfire in case that is helpful to anyone = http://www.youtube.com/watch?v=8oWoTvjciHo

So, if anyone has any thoughts that might allow me to narrow down the list of possibilities, it would be much appreciated. Thanks all!

-Justin

[kristen]

Re: Misfire with P0300

well start with checking your wires. make sure they aren't burned. then you can check you plugs to make sure you are getting spark.

[transamtom1]

Re: Misfire with P0300

More than likely the coil pack.

Between $35.00 and $50.00.

[whitdog54]

Re: Misfire with P0300

pull your plugs and check them.

I agree with coil packs though, usually thats what causes the p0300 and not telling you which cyl he misfire is on.

If you have someone local with HPtuners they could plug in and tell you which cylinder is misfiring.

[transamtom1]

Re: Misfire with P0300

Autozone will read your codes for free.

[whitdog54]

Re: Misfire with P0300

Autozone will read your codes for free.

he already has the code......

[transamtom1]

Re: Misfire with P0300

he already has the code......

My code reader gave me that code as well and also showed what cylinder it was.

It makes life a whole lot easier when you have the detailed code.

[whitdog54]

Re: Misfire with P0300

My code reader gave me that code as well and also showed what cylinder it was.

It makes life a whole lot easier when you have the detailed code.

ok well you werent being specific. He already had the code. Like i said. You should have told him that autozone will tell you the cylinder. I didnt think they did that.

[Justin.Kirkham]

Re: Misfire with P0300

Unless I am confused, the P0300 code is non-specific with regard to the cylinder. If the last digit of the code is a number, then that specifies the cylinder (i.e. p0304 means cylinder 4 is misfiring). So, though I would like to know the cylinder, the only code I am getting is a p0300, which does not specify.

Back on topic, if anyone else has any hunches of what it could be, I am open to them. I will be checking all the plugs, wires, and coil packs this Saturday to start with.

-Justin

[Justin.Kirkham]

Update

I replaced the spark plugs, wires, and the 3/6 coil pack, and now the misfire is gone. The 3/6 coil pack gave a resistance reading that was about 9,000 ohms, when it shouldn't be any higher than 6,500 ohms. So, it seems that the coil pack was the problem, which is a little strange, because I replaced that same coil pack 3 years ago, but oh well, she's running good now.

Thanks for all the responses and all the input!

-Justin

[ssms5411]

Re: Misfire with P0300

Good to hear, it is more cost effective to go through and test each componet and find your problem. Congrats.

[timthescarred]

Re: Misfire with P0300

Did you see any signs of rust on the old coil pack? If your replacing it within 3 years it might be getting some water dripping on it.

As for which cylinder a p0300 is, p0300 means multiple/random cylinder misfire which says that more than one is misfiring. However a dealership has a device called a TechII which will give you a Count per cylinder of # of misfires. (i.e. cylinder 2 - 1047 misfires cylinder 4 - 432 misfires) It's pretty awesome, and if your nice enough about it sometimes they'll do that for free.

[whitdog54]

Re: Misfire with P0300

Thats wierd that you have had to replace the coil pack twice now. Are you going with stock replacement or some autzone one? Im not sure butm maybe ICM can cause coil packs to go bad....but im not sure.

Saw that you are in hartford. You should check out Marks cruise night in e. granby CT. They had firebird week last monday. Not sure whats this monday, but its the biggest show this side of the mississippi

[Justin.Kirkham]

Re: Misfire with P0300

UPDATE

So... As I said previously, it was running great... until this morning.

I went out to start the car, and now the misfire is back, and better than ever. It now seems like a stumbling/stuttering misfire, especially prominent at low RPMs and during acceleration, and the battery voltage and RPM's both jump around whenever the car starts its shimmy and shake. The codes are P0300 and P0138, though I think the second is due to my Edelbrock exhaust and high flow cat.

So, I am thoroughly confused now, as replacing the parts I did made the car drive entirely symptom free for two days. Any advice?

-Justin

P.S. Could my car just not like Monday mornings? :p

[timthescarred]

Re: Misfire with P0300

Check your fuel pressure, could be a bad FPR or even just a clogged fuel filter.

Any other problems like hard starting?