Engine Miss @ Higher RPMs/Full Throttle

[C.K. Piquup]

My`91 6.2 Suburban sputters,misses,and pops when flooring it once it gets the RPMs up.Starts and runs great other than that.It seems worse with the engine not completely up to operating temp.I am leaning towards changing the injectors.I bought it at 96,000mi.and it now has 130,000.As far as I know they are original.I get a good bit of smoke out of the left side went I punch it sitting still and alot less from the right side.It started doing this about a year ago.I changed the filter then and it helped some for awhile.I`ll defiately change that again.I have almost new hi-pops from my roached`95 motor.I`ll be able to use these with all stock system,right?I have dual 3" exhaust with Dynamax round full-flow(no baffles)mufflers and would like to put a Peninsular marine I/P on it in the future.Any suggestions?

[john8662]

"sputters,misses,and pops" When this is happening, are you getting a lot of white smoke out the tail pipes?

Really could be several things, but lets start with the easy.

First off, change the fuel filter, it's for good measure, even if you'd changed it previously, as it's been while.

Second, It's time to get the clear 1/4' ID tubing out and install it on the fuel return of the injection pump. This will give you and idea of if you're getting air in the system, which would cause a very poor running condition.

I'm not so sure that you've got an injector issue here, and I don't think that the hi-pops would work very well in the 6.2 because of the lower pressure generated by the 6.2 pump. But they physically work in the engine, so for troubleshooting they're worth a try.

[C.K. Piquup]

Thanks for the reply,John.The only smoke is on start-up.Just a small cloud,mostly from the left.It will make smoke when I mash it sitting there.The vehicle has great power,so it`s getting the fuel.Maybe not enough at maximum demand.I first noticed this miss after it sat last summer while I slowly installed the new suspension(hardheaded hardware).I changed the filter then.I can`t remember,but I don`t think the miss totally disappeared.I`m putting another on.I was worried it could be a head gasket leaking into one cylinder when parked and causing poor firing until burned off.And,that could be causing a build-up on the injector or in the combustion chamber hurting flow.Is that possible?

[BobND]

Tee into the fuel line just ahead of the IP, and connect a low pressure gauge. Drive the unit while keeping an eye on the fuel pressure, while you duplicate conditions that cause it to missfire.

The IP needs fuel supplied to it at least a couple of PSI at all throttle postion and load conditions, or it won't be able to maintain the correct injection advance, and problems like your's will occur.

[G. Gearloose]

Sounds like it needs a little bump in timing to me. Yup, always start with the easy stuff.

[jonflies]

Did you ever figure your problem out? I'm online today for hard start and miss/low power.

[C.K. Piquup]

Haven`t figured it out,or tryed to be honest.I`m getting a fuel filter today and see what happens.It was doing pretty much the same thing this time last year,but with more of a lowered power problem.Still feels pretty strong this time.I`ll get back on here with the results .Your problem sounds like a pump and/or injector problem.Mine fires right up.

[john8662]

Don't forget the clear tubing on the fuel return on the injection pump to check for air while running after getting the new fuel filter purged.