I keep getting a P0300 code on the truck and it comes on and off as it pleases.

I am in the process of changing wires, waiting for them for come in the mail. Changed plugs I am running AC Delco 41-110 plugs and I have a set of AC Delco wires coming.

I had the truck on the scanner the other weekend and we were watching the firing and every cylinder was miss firing at idle and would not miss a beat at 3K RPM.

If any one has any idea's I am open to listen and try them out.

 

Any driveability issues?

 

Does it make noises like popping when you get on it? Could be a small crack in the porcelain of a plug, or could be the wires. From my experience it usually isn't the coils.

 

Not really any problems driving it. I heard many different things that it could be so I guess it's just a process of elimination. Wires are going on tomorrow morning. They just arrived tonight while I was at work.

What about the fuel filter? Could that have anything to do with it ideling rough?

 

Well, since you're getting misfires on all 8 cylinders, there has to be a problem across the board. Fuel filter would affect all 8, but should give you problems at more than just idle. Any recent mods that may have had an affect, like a cam or converter swap? I believe that a smaller torque converter could cause false misfires since there is less rotational mass that will affect crankshaft/connecting rod speed. Aftermarket cams are also known to give false misfires and the misfire monitor usually needs to be softened up to accommodate. If the misfires were above 4k I'd point to cat converters, but that's not the case here. How's the AF look? Any chance of a slight vacuum leak? You could try cleaning the MAF for ***** and giggles but that's kind of a shot in the dark.

 

The intake tube clamp was off of the throttle body, that could have a play in what is going wrong. Change all of the wires and plugs. So far so good.

Also did put a 2800 stall converter in when the trans took a dump.

 

Mine was doing that a few weeks ago even after I replaced plugs and wires, but it seems to be fine now a few weeks later...

 

How'd those new 90deg GM plug wires work with your headers?

 

Joe I will get some pictures tomorrow for you.

 

i have the same problem at idle. but the truck doesnt miss a beat under any load. i havent looked into this as of yet because its only at idle. if you find the issue please let me know. my truck just got the new iridium ac delco plugs and has the MSD wires. fresh fuel filter. stock air box with a drop in k&N.