turboescalade

iTrader: (10)

My friend has a 2001 GMC with a 6.0L and a couple minor mods like air intake and a wester's tune. He said it just started this past winter and it surges between 1900-2200 rpm on the highway. It doesnt do it around town, punching on it, or just accelerating. Only at a constant speed on the highway. I said it could possibly be a vacuum leak but it would always do it, not just cruising. Can someone help.

andrew383

iTrader: (14)

Sounds like the converter locking/unlocking

DR132

could be a funky throttle position sensor. how does it behave just idling?

03_Denali

iTrader: (1)

sounds like the lean cruise in the tune is active. Probably was too noticeable until winter blend gas.imo

Gadgetized

iTrader: (9)

Do you have the ability to log or check your AFR? It could be running lean, and that can cause a surge. It could also magnify this if the surge moves the timing into a different area of the table.

nonnieselman

iTrader: (10)

Could be a missfire?
when i first put MSD plug wires on my truck i had a problem like that, surging/missing. but only while cruising.
Put some cheap plug wires on it and no more problems.


Id check it for codes to begin with.

CalEditor@PCMCalibrators

iTrader: (4)

Westers tune

Can you data-log it?