P0300 code! Not finding help on Tech/Perf
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,216
Likes: 117
From: San Antonio Texas
P0300 code! Not finding help on Tech/Perf
Looks like I'll be needing an ignition diagram.(No, I don't have a manual yet) Anybody got a diagram appropriate for a 96 LT4 ignition that shows from the key switch to the plugs? The P0300 code says: multi misfires detected, but doesn't give any specific component to go after.
Car only has a little over 50k miles on it, but it is 11 years old now, and I'm thinking "dying Opti". I've checked for vacuum leaks and not found any. My A/C controller fix the day before is WAY too close for this to just be a coincidence. I'm thinking something on the edge of intermitten got disturbed under the dash. But now I have to find it
Car only has a little over 50k miles on it, but it is 11 years old now, and I'm thinking "dying Opti". I've checked for vacuum leaks and not found any. My A/C controller fix the day before is WAY too close for this to just be a coincidence. I'm thinking something on the edge of intermitten got disturbed under the dash. But now I have to find it
Burning Brakes
Joined: May 2006
Posts: 904
Likes: 0
From: Boynton Beach FL
Sucks man... I hate that code. Probably of absolutely no help to you, but I had that code on my 96 Yukon.
I changed all the O2 sensors, the knock sensors, full tune up, replaced cats, distributor, ignition coil, some other stupid sensor (spark advance something or other, I forget) and I NEVER got rid of that code.
I sold the Yukon and bought a vette.
I changed all the O2 sensors, the knock sensors, full tune up, replaced cats, distributor, ignition coil, some other stupid sensor (spark advance something or other, I forget) and I NEVER got rid of that code.
I sold the Yukon and bought a vette.
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,216
Likes: 117
From: San Antonio Texas
That's the main reason I shed myself of that damned old GT Mustang I had. It developed one of those "mistery" misfires. I changed the dist. coil, wires, plugs, harness, computer, ignition switch...everything on that car except the paint. I got to where I didn't want the stinkin' thing even if it ever did get fixed. Finally just changed the owner!
Le Mans Master
Joined: Oct 2000
Posts: 6,202
Likes: 9
From: St. louis, MO
Have you changed the plugs or wires recently? I got that code a little while back after changing the plugs and wires. Turns out I switched the #1 and #3 plug wires
, corrected them and car ran fine and code went away.
, corrected them and car ran fine and code went away.
Melting Slicks
Joined: Oct 2004
Posts: 2,283
Likes: 0
From: Leeds Alabama
send me your email and I will email you the gm diagnostic tree (but you really need a scan tool)
corvette95@charter.net
corvette95@charter.net
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
My only experience with a random misfire with code "was", two spark plug wires were touching metal parts and grounding out. I used zip ties to get the wires off metal parts and grounding.
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,216
Likes: 117
From: San Antonio Texas
Still Working on it.
I started under the hood by getting the air cleaner & mass Air off and out of my way. When I did that, I looked down into the mass air sensor, and the screen was full of bug wings and grass! I opened up the air cleaner box and found one corner of the K&N was not seated correctly and outside air was getting around it. Now I'm cleaning everything up and looking at all the connectors along the way too. I was cleaning up the throttle body which was filthy and noticed something stuck under the plate on top that says "Grand Sport". Well, there was a wrinkled up old gasket under there. I thought it was just a look pretty plate all this time. After finding two different part stores where the parts counter guys just stare back like deer in the headlights, I'm making a new gasket myself to put back in there. After I get all the cleaned air parts back on, I'm continuing my electrical tracing and do a fuel filter change as well. Everything I've touched so far has needed attention, so I'm touching everything I can get to. This might just be a stackup of many little things finally ganging up to make one big mess.
Race Director
Joined: Mar 1999
Posts: 16,950
Likes: 0
From: Stafford, Virginia Kittah, Kittah, Kittah...
Check out the short harness run that goes from the opti to the passenger side valve cover area, near the injectors... Mine went bad on the 96 LT1 I previously owned and gave the same indications... P0300 was also one of the codes I recieved... Considering you're getting multiple misfires, I'd look either there, the coil or coil wiring, and maybe the opti itself...
The dealer replaced the opti under warranty before they found out it was a $30 harness causing the problem in my instance...
The dealer replaced the opti under warranty before they found out it was a $30 harness causing the problem in my instance...
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,216
Likes: 117
From: San Antonio Texas
I've checked out all the wiring to the Opti & Ignition box and all had good connections thanks to GM's great weatherpack connectors. ( On my Fords, they couldn't have held water any better if they had put the connectors in a funnel!) The Opti is pretty nasty down there with lots of road grime mixed with a little oil that must be coming from either the front seal or the crank position sensor. The plug wires may have suffered because of that. I think if I have to do the wires I might as well pull the front of this thing off and do a new MSD Opti and fresh wires & plugs too. Still cleaning up the whole front of the engine. Man there sure is a lot of stuff crammed in there
!
!
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,216
Likes: 117
From: San Antonio Texas
I've had it!
Finally got everything cleaned up and back together. Rode around the block and it's still screwed up. Well, it goes in the driveway now and the wifes car gets its spot in the garage. I spent 2 years on another car with this problem, nobody could fix it. I finally just sold it. I got so sick of looking at that bastard I didn't care if it ever ran or not. I can't see the worth of sheltering something that won't run. I'm sick & tired of throwing money at it, and wasting what little time I have left. Screw the damn thing! I'll park it under the tree and let the squirrels eat it! Maybe somebody will want it next spring when they're full of energy and enthusiasm.
