00 Denali - Random Misfires under load

[SunlitComet]

I think I pushed out a gasket on mine testing at WOT after the KN FIPK install. Have not opened it up yet but cyl 4 and 6 are down to 3 psi. Happened instantaneously.

 

[TurboGSR96]

lol that doesnt give me much motivation for a blazingly fast 255hp (minus some) WOT test.

 

[BattelWagun]

true, but he was driving it, you're going to be doing this with the truck parked, and zero load on the engine. I think you'll be fine for a split second.

 

[SunlitComet]

Don't worry. As it turns out other then an alternator and fuel spider my drivetrain is all original so it was probably time for something to go.

---------- Post added at 01:59 PM ---------- Previous post was at 01:55 PM ----------

It looks like the valve seal may have been letting oil in #4 and this time during Wot( happings more then I would sometimes admit) it just got out of hand.

 

[gpracer1]

Turbo, I would start by double checking the spark plug wires and make sure they are on the correct plug and correct terminal at the cap. A vehicle can run with that messed up, just poorly like you describe.

Next I would pull the plugs and look at them.

While there, do a compression check.

Might as well put in new plugs anyway since they are out.....brand new plugs can be bad and they are cheap.

 

[TurboGSR96]

Turbo, I would start by double checking the spark plug wires and make sure they are on the correct plug and correct terminal at the cap. A vehicle can run with that messed up, just poorly like you describe.

Next I would pull the plugs and look at them.

While there, do a compression check.

Might as well put in new plugs anyway since they are out.....brand new plugs can be bad and they are cheap.

Thanks for the suggestions, I am certain a plug wire isnt switched it wouldnt run normally then not. Plugs are not the issue either is something much deeper. I would do a comp test but I am certain my issues are not due to a hurt or weak motor... it either the Pump, Distributor or a sensor of some sort.

 

[SunlitComet]

can you scan for a cylinder misfire history to pinpoint it.

 

[TurboGSR96]

The tool (more like a box) I have is not much more than just a plain jane scan tool and its a relic. There is no misfire reading or any of that, I am borrowing a friends fuel pressure tester tomorrow hoping I know more then.

 

[SunlitComet]

check with a parts store for a free scan if possible. Some do it.

 

[TurboGSR96]

This is what mine is producing right now and it is the factory unit from 236k miles ago.

priming 60psi

Priming stops engine not running 53 psi

engine running 52psi Jumps to 60psi when open wide throttle.

engine off 46psi drop to 45 psi in 5 minutes and holds that for at least 40 minutes.

If you get that then you are good.

If your are running like okay at idle and practically no power while opening peddle you are probably getting starved of gas. Just ensure you don't see anything else wrong before doing your pump and check it power connection too.

On key on I get a 60 spike that sits at 55psi no drop
At idle I get 50psi and jumps to 60psi when floored.

Well I guess its not the pump

---------- Post added at 01:05 PM ---------- Previous post was at 12:59 PM ----------

Anyone ever have issues with a clogged cat converter?