P0300 code Who's had one ?
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,218
Likes: 117
From: San Antonio Texas
P0300 code Who's had one ?
Got the multi misfire code. Looking for people who have actually HAD one of these nightmare codes and what did you have to do to fix it. I can't find anything really wrong like a vacuum leak or bad plugs or wires. What ever it is is well hidden. (Maybe some of the majic smoke got out of one of those sealed electrical boxes somewhere.
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Race Director
Joined: Aug 2000
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Cruise-In II Veteran
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,218
Likes: 117
From: San Antonio Texas
Checked most all that stuff. One day it runs great and the next day it can't get out of the driveway. Thanks for all the suggestions, but I've already been through them. I want to hear from somebody that actually HAD & FIXED this problem.I've been thinking about replacing that old Opti with a newer more dependable MSD someday, but when I do, I don't want to start off with it still having another problem in the mix.
Last edited by Klondike; Sep 10, 2007 at 07:37 PM.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
I had this fault and fixed it on my wifes car. The P0300 is usaly an ignition problem related to a the distributor or coil. Her car was not a Vette but rather a Sebring vert but same OBDII code and it was also intermitant. On her car everything including the coil was in the distributor and I replaced it and the problem stayed the same. After Months of checking everything under the sun, Plugs, wires, CPS, Fuel presure, Injectors etc... I finaly decided I had to have recieved a bad distributor, well I replaced it and the problem wqas fixed. Only I could manage to buy a part with the exact same problem as the original. For our cars if you have checked the plugs and wires I would suspect either the coil or the Opti.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Shop Manual will help you diagnose it - but out here, usually clogged injectors; so much so, that GM issued a special 200K injector warranty to avoid a CA recall - '96 through ? - Bulletin outlines cleaning procedure - all on GM's dime. Problem linked to MTBE in the fuel - now banned. I would suspect same, but given your Opti Ignition, that too is a logical choice along with water in the fuel (or any foreign substance, I've duplicated by simply spraying too much TB Cleaner on OB2 cars), particularly if your Vette sits, or the problem occurred after you topped it off.
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,218
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From: San Antonio Texas
As much rain as San Antonio has had this year it wouldn't surprise me to get water in the gas. But it ran just fine the day before with the same gas fill. After I messed with it and cleared the code, it ran good again for a few minutes..then popped the code and ran crappy again. Almost like it was heat related to warming up to running temp. That could be a coil breaking down I guess. I'm starting to pull things off and check connections and OHM them out. The coil will be one of the first tests.
8th Gear
Joined: Nov 2005
Posts: 8
Likes: 0
From: AUSTIN TX
This sounds very close to my problem. I know the car got rained on really hard months ago. The 0300 code showed up with a half miss the next day. The area under the gas door was full of water (the drain was stopped up) too. My fuel gauge showed empty one day and then full the next. I drained and ran all the fuel out and replaced it with new fuel, water out, and fuel inj. cleaner. Now the gauge says full all the time but the range gauge is dropping. Anyway I think the water was the real problem all along and do not want to replace the opti, etc. Let everyone know if you solve it. The car was fine before the rain.
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Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,218
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From: San Antonio Texas
Still workin' on it.
Finding all kinds of little stuff to fix along the way. Dirty mass air, Dirty throttle body with a goofed gasket. Checking all the connectors for loose pins & corrosion.(they all look clean & tight inside. GM did a good jub with their under hood connectors.) Oily filth under everything I've pulled off. (Looks clean from the top though) Ohm'd out the coil but don't know what it should read. (did another post for Ohms on LT4 coil.) It has plug with 3 pins in it. It measures .3 ohms between any 2 of the three pins. Measures 5.8K from the HV tip to any one of those 3 pins. I just don't know what is normal for these, so I'm waiting for a reply either here or on my "Ohms on LT4 coil" post before I start reassembling stuff I've pulled off.
P.S. Thanks for the water tip.I drove through a freaking MONSOON in the Texas panhandle on the way back from Colorado about 4 weeks ago. I still have a little of that tank left, So I'll be checking it for water too!
P.S. Thanks for the water tip.I drove through a freaking MONSOON in the Texas panhandle on the way back from Colorado about 4 weeks ago. I still have a little of that tank left, So I'll be checking it for water too!
Last edited by Klondike; Sep 17, 2007 at 11:32 PM.