I'm a newby on this forum and hoping someone can help me with a recurring problem. My silverado has started to miss and buck when I start out in the morning and will continue doing that for anywhere from a few minutes to an hour when I'm on a longer trip. It's an intermittent problem - sometimes I'd take it to my mechanic and leave it overnight and the next morning it would start right up and cruise away like it was new. Next day, I'd start it, and it would go all to hell. The symptoms are these: starts with no problem - fires right off; it will sit and idle happily without missing at all; as soon as I start off it'll seem okay until I get to around 2000 rpm and then it will miss and buck continuously for as long as it wants to and then maybe settle out in a few minutes and maybe not; if I punch it, it doesn't seen to buck, but if I back off, it'll start missing again.
I finally got fed up with it a few weeks ago, replaced the fuel pump (the pressure was lower than spec), replaced the ignition wire set, and replaced the ignition module and most of my wallet. Seemed to run better for a few weeks, but now back to its old tricks.
The engine is a 4.3 and has about 65K on the clock. It's been well taken care of - the biggest problem I've had is when the local gas stations changed over to E-90 and, if I let it sit for a while, it would refuse to start until I crawled under it and replaced the fuel filter. I did that for about five times until I found a gas station that serves "classic gas" - (no ethanol...) and I run with that pretty much full time. I run a shot of fuel injector cleaner every now and again - but to no good effect.

Any advice or suggestions would be most welcome. My mechanic is really top notch and we're both scratching our heads at this point.

Many thanks.

 

Fuel pressure regulator. Haven't done this yet on my truck but it sounds like it could be your problem.

But try cleaning your MAF sensor and throttle body, maybe run Sea Foam through it. That might help.

It could also be a knock sensor but I am not 100% sure what the symptoms would be. Does it knock at all?

 

mine did the same thing. it would idle fine for a while then just start missing. and it would run fine down the road sometimes and then start to do it again. mine was the intake gasket or check o2 sensors. they replace the gasket and 1 o2 sensor and works fine for 10 months. just something to look into.

 

Thanks for the suggestions - we did check the fuel pressure and pressure regulator - the pump pressure was low and that's why we replaced the pump. It doesn't knock at all - it just runs really poorly when it starts out and sometimes settles out and sometimes not.

 

I'd check fuel injectors and fuel pressure regulator.

What's your current fuel pressure?