This 0300 code is ******* me off!!

[Declansdaddy]

So I've been dumping bookoos of money into this thing (which most is general maintenance stuff anyway) and I'm still getting my 0300 (random multiple cylinder misfires) code. I've replace plugs, wires, coil packs, did the EGR port clean out, replaced a leaking exhaust manifold, and did a new EGR tube while I was at it. Truck also has a new DPFE sensor and those vacuum lines. I've looked over all vacuum lines and sprayed carb cleaner around every gasket and hose while running to try and find any vacuum leaks. Then I got to thinking today maybe I'm looking in the wrong direction. Does anyone know if clogged injectors would cause this and throw this code? I would think a lean cylinder code would pop up but I figure it's worth a look. I can clear the code and drive the truck around normally and the light will not come on but if I'm towing my boat or getting on it hard that's when I get the code. I'm planning on getting some fuel injector cleaner regardless however I'm curious to see anyone else's thoughts.

 

[BAD RONALD]

A fuel problem can cause misfires. What part of the fuel system may be causing trouble to more than one cylinder more than once is the question.

Injector inspection is as good a place as any to start looking. Always a good idea to look for simple solutions first.

 

[devincox]

Don't know if this helps, but here is my experience.

I owned a 98 expy that now has 236k on it and gave it to my son, who has been driving it for the last 4 years or so. I just received a 97 EB Expy with 225k on it. I have had to deal with that code many times.

For me it was always the coil packs shorting out on some type of fluid (coolant, oil, condensation).
On my 98 4.6, it was the condensation from some metal line back against the firewall ( AC, I think. It's been a while. )

On my newly acquired 97 5.4 , I got the same problem and it ended up being the intake manifold gasket leaking and the spark plug wells were filling up with coolant and then shorting our the cop.

I replaced the intake gasket and valve gastkets and then all the cops and it has been running like new for about 500 miles. I dont drive it much yet.

Devin