PCM Code 300 -- Misfire, help?!?
Thread Starter
Supporting Vendor
Joined: Jul 2003
Posts: 6,486
Likes: 2
From: http://www.mphparts.com 800-364-1975
PCM Code 300 -- Misfire, help?!?
Hi,
I'm getting PCM code 300 on my DIC. About two weeks ago I installed TR6 plugs gapped at .55. They ran better than the old plugs but I was getting no codes.
I gapped them down to .40 based on recommendations from this forum, and now I'm getting code 300.
Is it possible I damaged a plug or something on the engine? I saw in previous posts that someone suggested checking the coil packs and looking for some exposed wiring there.
Any help is appreciated. My car is still under warranty and is only lightly modded so I don't expect too much of a hassle from the dealership, but you never know...
I'm getting PCM code 300 on my DIC. About two weeks ago I installed TR6 plugs gapped at .55. They ran better than the old plugs but I was getting no codes.
I gapped them down to .40 based on recommendations from this forum, and now I'm getting code 300.
Is it possible I damaged a plug or something on the engine? I saw in previous posts that someone suggested checking the coil packs and looking for some exposed wiring there.
Any help is appreciated. My car is still under warranty and is only lightly modded so I don't expect too much of a hassle from the dealership, but you never know...
Advanced
Joined: Jun 2003
Posts: 52
Likes: 0
From: UpState NY
Re: PCM Code 300 -- Misfire, help?!? (diynoob)
A couple months ago I had new wires put on my 2000 corvette during a Header installation. After picking up the car from the garage I received this Code 300. In the end it was the wires! They were a brand new set with a defect. I had the garage install a new set and the Code 300 went away. Can't even trust a new set a wires right out of the box.
Le Mans Master
Joined: Jan 2003
Posts: 7,161
Likes: 5
From: Richmond VA
Re: PCM Code 300 -- Misfire, help?!? (diynoob)
I would go to the exhaust pipes and listen carefully to the idle of the car. If the car is idling funny, you probably gave either a loose wire (either on the coil pack end or spark plug end) or a problem with one of the spark plugs.
Burning Brakes
Joined: Jul 2000
Posts: 883
Likes: 3
From: wilmington DE
Re: PCM Code 300 -- Misfire, help?!? (diynoob)
I've got the same code plus the check engine light. I've checked the wires & they seem tight. I'm going to pull each one & reinstall tonite & see if that will correct the problem. Car runs very rough like it has a loose plug wire, but they all seemed tight.
Premium Supporting Vendor
Joined: Oct 2001
Posts: 8,392
Likes: 572
From: Dallas Tx
St. Jude Vendor Donor '03-'04-'05-'06-'07-'08-'09-'10-'11
Re: PCM Code 300 -- Misfire, help?!? (stevenll)
Usually just pulling the old wires off and on a few times will cause problems with the ends. If this is not the problem, then maybe one of the plugs got cracked on install. It is not hard to crack a plug.
Ig you can get a hold of a Tech 2 you can find out which cylinder is the problem and save some time.
I would focus on these two areas first.
Hope this helps.
Lou G
Ig you can get a hold of a Tech 2 you can find out which cylinder is the problem and save some time.
I would focus on these two areas first.
Hope this helps.
Lou G
Thread Starter
Supporting Vendor
Joined: Jul 2003
Posts: 6,486
Likes: 2
From: http://www.mphparts.com 800-364-1975
Re: PCM Code 300 -- Misfire, help?!? (diynoob)
Thanks everyone,
Yes, the car is idling a little rough. That is why I regapped them this weekend, hoping it would eliminate the problem. I will check the wires and try to get ahold of someone with a tech 2.
Will misfires damage the engine over time or are they just hurting performance? Since regapping the plugs I have noticed the car runs GREAT, better than it did before, even with the misfires!
Yes, the car is idling a little rough. That is why I regapped them this weekend, hoping it would eliminate the problem. I will check the wires and try to get ahold of someone with a tech 2.
Will misfires damage the engine over time or are they just hurting performance? Since regapping the plugs I have noticed the car runs GREAT, better than it did before, even with the misfires!
Burning Brakes
Joined: Jul 2000
Posts: 883
Likes: 3
From: wilmington DE
Re: PCM Code 300 -- Misfire, help?!? (stevenll)
I pulled the plug wires last nite & 2 had very low resistance & the metal connector stayed on the plug with another. Hopefully a new set of wires will cure this problem.
Burning Brakes
Joined: Aug 2000
Posts: 1,218
Likes: 1
From: MD
Re: PCM Code 300 -- Misfire, help?!? (stevenll)
Gaped at .40 ?. I missed that one. I just replaced wires and plugs. Got MSD Wires and TR55 Iridiums. I had a rough idle and an occasional mis-fire. Car now idles smoothly at 700 rpm and runs great.
I would replace the wires, and check the plugs.
Hope all works out.
:flag
I would replace the wires, and check the plugs.
Hope all works out.
:flag
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
