Jaguarxjr@1968

Car ran perfect for 240 mi. Did intake and vc gaskets too.
Again NO updates on CURES for these P0300's lol WWHHYYYY I have reman PCM and BCM, (BCM was bad thats why I got the car for $1650) new plugs/wires, opti from a running LT4 with 36k miles that was parted out that I heard run fine, new fuel pump, new fuel pressure regulator. I have the WET #1 plug even managed to get a code 301 for that and then drove it again went to P0300, found an arcing coil wire, replaced that, fuel pressure is good, had codes for 02 but it was intermittent. ALL injectors are firing.

Then last night CRANKED FORVER to BARELY start then ran rough then oddly the BOTH fans came on out of nowhere, what is with these cars man I am ready to sell as is. Any help would be super appreciated. I have never seen such a mess with these LT1's ever.
RAN GREAT for 240 miles then all this crap started.

AZSP33D

It's a generic misfire code. Some modern cars have a lot of diagnostic tools, the 1996 just has the basic federally mandated
OBDII to tell you there's an emissions related issue.

Googled it for reference, here's something I found that summarizes the strategy to repair:

A code P0300 may mean that one or more of the following has happened:
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked/leaking EGR valve / passages
Faulty camshaft position sensor
Defective computer

Common knowledge and widely available information out there for trouble-shooting OBD II stuff. Don't expect someone to tell you it can only be one thing.

Jaguarxjr@1968

Thanks for the info. Just hoping people would post what cured their issue with this code.


Faulty spark plugs or wires )Both New
Faulty coil (pack) )coil works fine.
Faulty oxygen sensor(s) ) Did get a code for after cat ones a couple x and bought them just haven't installed code hasn't come back.
Faulty fuel injector(s) ) All are firing fine, did a noid and steth.
Burned exhaust valve, )do not think so I knew the previous 70 year old owner and did a comp test all was good.
Faulty catalytic converter(s) )They are fine.
Stuck/blocked/leaking EGR valve / passages, Original works.
Faulty camshaft position sensor )Haven't changed it.
Defective computer )HIGH on my list the CLOWN that did my pcm and bcm, is horrible had to send the bcm back to get REDONE and now since all this crap started I am seeing my MPH ornage flicker when I rev it as will as volts when I rev it.

I got it for $1650 because the BCM was bad just started and ran for 4 sec then dies, no MPH lit on dash.

AZSP33D

I've cured it by removing the fuel injectors, putting them on the flow bench (I have one of those cheap Fuel Injector Test setups from China) then replacing three of them (actually removing the filter screen, cleaning in the ultrasonic cleaner, and backflushing wth odorless mineral spirits.) The lazy man's cure for the same disease is to replace the injectors with new (although I've tested new injectors that didn't work well). But we don't necessarily know what the disease is, only the symptom.

I would change thinking from something like "we still haven't cured the cough that's been around for eternity, and millions of years later, nobody can tell me how to cure the problem"... to here's a clue, a fault code based on the diagnostic functions of the ECM, let's see if we can troubleshoot. You could theoretically check on an automotive diagnostic occilascope and get more clues. The FSM will provide a road map to the proccess.

Jaguarxjr@1968

Mine ohm fine and are working , this all hapened in a 4-6 min interval the other day while driving. I think the newer C4;s are different when it comes to this code, I could be wrong.