JOHN1L40

I have checked and\or replaced the following:

plugs
wires
injectors
coils
fuel filter
fuel pressure
maf sensor was replaced a year ago, dont know how to test??
vacuum leaks
cleaned throttle body
transmission
AFR good
New O2 sensors

I get a stumbles in these senario's

just taking off, real light throttle, will stumble if I hold throttle just barely open.

Highway speeds, TQ converter locked, steady rpm around 2200. If I lightly start to add more throttle I get a stumble. If I hammer it I dont get a stumble.

Truck runs great, strong revs fast and pulls hard. What else could I check???

Wheatley

iTrader: (12)

Pump?
Did you check the fuel pressure under a load or just at idle?

therock

iTrader: (2)

I'm gonna call it the throttle body position sensor of sorts. You are drive by cable so it's maybe on the TB.
Can you borrow another TB?

JOHN1L40

I checked the TPS and I get .5 volts at closed throttle and 4.5 volts at WOT. I think this is within specs.

JOHN1L40

I checked pressure under both. I am at 58 psi idle, no vacuum attached, with vacuum attached it drops to 52 psi at idle. It climbs under load all the way to 66psi under boost.

Like I said it is strange as the issue is light throttle light load and light throttle heavy load both but always small throttle openings.

JOHN1L40

I tested the stumble this morning before the truck was up to full temp and it doesn't stumble. What could cause this that changes as the truck temp reaches full temp??

I run a 160 thermo so the max temp usually sits around 174 on the scanner.

Hugger

iTrader: (21)

My truck seems to stumble right after it shifts to second under light throttle. Let me know if you find out what is wrong with yours. I haven't logged mine yet so I don't have a clue what could be wrong.

Truck is 04 GMC Sierra ECSB

dlt76028

iTrader: (13)

had same issues on a friends truck, it was a small crack in the porcelain of a spark plug.

therock

iTrader: (2)

I had it a few times before full temp less than a mile from home. Taking a right from a full stop and gently pressing the pedal it would stumble in 1st gear and take off or clear up the second I let off. Maybe happened 5 times over a month.
I have an 05. I took the gas pedal out and tested the position device and it was ok. I cleaned the TB real good and it has never returned.
Not sure if I did anything to rid of it or not. Good luck.

JOHN1L40

IWish that was all it was. Already tried new plugs no change. I have a new maf comming, I think the slight oil blowbye of the turbo is hard on the sensor.