Misfire Code

[davha]

Hello

I have a 03 Silverado 5.3L Vortec.

Here is the problem. Somtimes takes a few tries to start. Idles ok but there is a slight stutter at idle. Start driving and as rpms increase it shakes (running rough)

Bad around 2000- 2500rpm. Smooths out when ya floor it but lacks in power at that point. Code p0300 and p0449. From what I've seen so far p0449 shouldnt cause that. So I changed plugs n wires. No change. P0300 random/ multiple misfire

I had just got the truck recently. Was told they narrowed it to number 8 cyl. So I also changed that coil pack. What would be the best next step. To solving my problem.

[txab]

Check fuel filter. Check fuel pressure, reading at key on, engine off. Check for intake leaks

[davha]

Could it be egr valve or some kind of relay? I will look into the fuel pressure.

[txab]

Check fuel pressure regulator as well. Look for presence of fuel when you remove the vacuum line, if present FPR is bad

[silveradosid]

i would suspect a bad injector or sticking injector try injection cleaner

[davha]

Fuel pressure is ok. Diagnostic machine saying both banks are lean. Gonna spray around intake and hoses tomorrow when tipped:) Im new and need neighbors. add davhatruck is cold. Thinking intake or hose leak.Or MAS is bad. As of tonight. I have injector cleaner that I'm going to use. Will be looking into those as well. Thanks for the help. I will update tomorrow night.

[txab]

What was FP reading? Key on Engine off?

[davha]

Fuel pressure was a little over 50. From what we were reading. It is supposed to be between 50 and 62. We sprayed all around intake and vacuum lines today when truck was cold. No apparent intake or vacuum leaks. Will be looking into fuel pump and electrical connections. I guess there is a history of the connectors at pump going bad.