Intermittent p0304

[quadboy75]

I have a 2000 z71 tahoe with the 5.7, old body style, been having issues with an intermittent code p0304 and misfire when pulling a hill, in town and on flat ground it runs and idles perfectly. I’ve replaced the tps, map, plugs and wires, cap and rotor, and coil all recently. The intermittent problem was there before I replaced everything and is still there now. Any help would be appreciated.
Also, compression test shows 160 on basically all cylinders, 260k miles, and I know it has a faulty speed sensor that I need to replace.

 

[quadboy75]

I have a 2000 z71 tahoe with the 5.7, old body style, been having issues with an intermittent code p0304 and misfire when pulling a hill, in town and on flat ground it runs and idles perfectly. I’ve replaced the tps, map, plugs and wires, cap and rotor, and coil all recently. The intermittent problem was there before I replaced everything and is still there now. Any help would be appreciated.
Also, compression test shows 160 on basically all cylinders, 260k miles, and I know it has a faulty speed sensor that I need to replace.

Also, the hill that I can get it to miss on every time is a 7% grade for about two miles out of a 35 mph curve, at the top when you reach about 50-55 and it starts to level out is when it starts vibrating from the miss and trips the light, shortly after shifting into high gear.

 

[Eman85]

Can you make it miss powerbraking it?

 

[quadboy75]

Can you make it miss powerbraking it?

Haven’t tried that

 

[exp500]

Does your tach "bounce" occasionally? About a 1-200 rpm swing. Have you tried in injector cleaner in the gas? Have you adjusted the valves?

 

[quadboy75]

Does your tach "bounce" occasionally? About a 1-200 rpm swing. Have you tried in injector cleaner in the gas? Have you adjusted the valves?

I run injector cleaner every oil change, Lucas, and have for years, the tack does jump up a little just before the miss and the engine revs a little like it’s almost hitting passing gear. And no I haven’t adjusted the valves. It runs like a ***** ape in town, you step on it from a stop and it takes off without any hesitation.

 

[Hoesgottaeat2]

Another one to throw at it would be to clean the MAF sensor.

 

[quadboy75]

Already did that too, sorry I didn’t mention that

 

[quadboy75]

Haven’t tried that

Update, tried powerbraking several times, both from a standstill and at around 40 and no light no miss.

 

[east302]

Do you have a scanner to see individual cylinder misfire counts and check the fuel trims?

Since it’s specific to cylinder #4, a barely-faulty injector could be a culprit since you look to have replaced the ignition components with no change. Are these the original injectors and have you checked the fuel pressure? Spec is 60-66 psi with key on, engine off.

When were the lower intake gaskets last replaced? Any coolant loss?