hello I have a 02 Silverado 2500hd 6.0 4x4 and im getting misfires bad, p0300 code and also a egr code p0404 and 02 p0134 codes. I checked the intake gasket for leaks . cleaned maf and throttle body decently. I also pulled a plug but cant tell if its bad or not, cylinder 1 is where the misfiring starts according to scanner. my question is where do I start? buy a egr first? ( cheap china one on there now) or buy a 02 sensor (sensor 1 bank 1 upstream) ? or plugs and wires? any help appreciated . Original Postersbrewer74 (steve)Newbie
Posts: 2Topics: 2Joined: Mar 20 2019, 12:01pmLocation: bostonYear: 2002

 

Well if you can't tell if a plug is bad I'd change those first. After that, you can tackle the rest once you see if anything happens..

 

just for giggles i would check fuel pressure

 

I'd go after the EGR because if it's either malfunctioning by opening too much or remains stuck open, it'll create both other codes. Check to see if carbon is stuck in the EGR pintle. I've removed EGR's in the past and give them a good cleaning along with a good smack on a board that breaks any carbon buildup located at the pintle seat.

 

On the same subject. I got a p0300 code on my Express 2500 but I then cleared the code and it did not come back. No other codes.
Should I be concerned or leave it alone. It runs fine. It is the base for a 28 ft class C rv.

Thanks

 

Personally, I wouldn't be concerned...reason being that P0300 misfire is sort of a generic code. It, by itself, could actually be attributed to something as simple as poor gasoline quality. Even a stumble upon cold starting due to gummy injectors from an engine that isn't regularly run on a daily basis. As fuel is used when started, the detergents in the fuel generally clean them up. P0300, by itself, is looked upon as a "soft" code. It's real use is when there's multiple codes...it's an affirmation to another problem that's effecting the engines performance.