P0300 at high RPM

[heresjimmydean]

I have a 99 Firebird Automatic that is lightly modded. When I floor it, around 6000 RPM my SES light comes on. When I scan it the code is P0300 random miss fire. I've changed spark plugs, wires, and coils. Are there any other likely possible parts that could be causing me to throw this code? Why am i only throwing it at high RPM's?

P.S. I did search first and went through the first 4 pages of results but I don’t really have the time to go time to go through all 100+ results. If this has been discussed before please let me know so I can go read them and I don’t waste more of your time than necessary.

[bigbrian442]

Re: P0300 at high RPM

Try doing a case Relearn.

[N2OEQIP]

Re: P0300 at high RPM

why dont you list your mods so we can let you know where to start from.

[N2OEQIP]

Re: P0300 at high RPM

and you do know 5500 is at the verge of redline..... How much past 6000 are you reving this???

[ssms5411]

Re: P0300 at high RPM

A bad injector could cause a misfire if it is starting to go out plus the high rpms a little fuel flow if the injector is going out. Mine did this for about a year before with the PO300 code before I found out it was a injector. I wish it would of thrown a cyl. or injector code but it didn't.

[heresjimmydean]

Re: P0300 at high RPM

My car shifts from 1st to 2nd right around 6000 rpm, which is when the light comes on.

Mods: Performance cat & cat back, intake silencer!, Wisper lid, K&N air filter, MSD 8.5 wires, MSD coils, Tuned PCM.

[techsan23]

Re: P0300 at high RPM

My car shifts from 1st to 2nd right around 6000 rpm, which is when the light comes on.

Mods: Tuned PCM.

I think bigbrian may have pointed out your problem. Was that a mail order tune, or did someone tune your pcm? Did you perform a case relearn after the pcm work was done.

[heresjimmydean]

Re: P0300 at high RPM

Mail order, and no. long story short, i was told that it wouldn't do anything if i had a case relearn done. After doing my research on case relearns, im gonna go do that. thanks a ton. if this doesn't fix it, i'll let you guys know.

[bigbrian442]

Re: P0300 at high RPM

Stock shift points are 1-2 5700 and 2-3 5500. I can see the mail order tunes moving these up a bit.

[bwkmaro]

Re: P0300 at high RPM

plug gaps wrong?

[whitdog54]

Re: P0300 at high RPM

Clean your MAF, maybe a new fuel filter. Just small stuff, but you never know.

Was it a PCMforLess tune? Never really heard anyone having problems with them.

[FreakV6]

Re: P0300 at high RPM

^^ i had an awful experiance with pcm4less, but thats a story for another day lol.

i would also check out the icm(what the coils mount too). some auto stores have a tester that will check it out.