stumbles at off-idle -dealer stumped!
92 GM 4.6 engine:
Got the dealer stumped even. Sold me a head then said I need a new engine. So a new head later, it is still stumbling under load.
I have returned a fairly new MAF to AUtoZone for a replacement. No change. I have a set of plug wires that are on lifetime warranty- they said bring 'em in for a replacement. So, I am going to put a new set of plug wires in. It is still running rough- not too bad at idle; but off idle it stumbles. No smoke so I am thinking that the rings are OK. That being said, is it the coil pack or the fuel injectors? I have to believe that after replacing all other components that are the likely culprit: EGR, EVR, IAC Thermal Coolent Sensor, both 02 sensors, PFE. Iam running out of diagnostics. There is a new head on the pass. side. Fuel filter is new, fuel pressure is good at 42... injector set about $200. Coil pack about $100.
How can I test either?