My 2004 ENVOY 187K mile 4.2 sounds like an old man getting up in the morning. Races up to 1800 then drops off a cliff and slows till its about to stall with loud knocking, then races up again to 1800 with lots of sputtering and coughing in between, then stabilizes around 1000 slowly lowering to it's purring idle speed of 625. All this drama takes about 1 minute.
Its as if the PCM is getting some very bad info from the rest of the team and is tinkering with the timing while trying its best to juggle the air/fuel mixture to please its owner, (me).
No codes. Runs very well the rest of the day. Coils are all firing. Pulled 2 plugs which are tan and dry although the pin the spark jumps to seems very pointy. VVTS connector has no oil in it. No vacuum noises. I spray MAF sensor at each oil change. Tried a 5 minute MOTOR MEDIC Motor Flush before last oil change. Didnt help.
Dont want to start throwing parts at it but wondering about:
VVTS, maybe its clogged. FUEL PRESSURE REGULATOR, its the original. TEMP SENSOR, but its giving normal temp readings to dash cluster.
My 03 Trailblazer did the EXACT SAME THING at 275K before I sold it but also ran great after the first start up of the day
Outside temperature is in the 60s, this is Florida.
With no codes I'm stumped.
Some of you must have had this problem at high mileage. What was the fix ?
Its as if the PCM is getting some very bad info from the rest of the team and is tinkering with the timing while trying its best to juggle the air/fuel mixture to please its owner, (me).
No codes. Runs very well the rest of the day. Coils are all firing. Pulled 2 plugs which are tan and dry although the pin the spark jumps to seems very pointy. VVTS connector has no oil in it. No vacuum noises. I spray MAF sensor at each oil change. Tried a 5 minute MOTOR MEDIC Motor Flush before last oil change. Didnt help.
Dont want to start throwing parts at it but wondering about:
VVTS, maybe its clogged. FUEL PRESSURE REGULATOR, its the original. TEMP SENSOR, but its giving normal temp readings to dash cluster.
My 03 Trailblazer did the EXACT SAME THING at 275K before I sold it but also ran great after the first start up of the day
Outside temperature is in the 60s, this is Florida.
With no codes I'm stumped.
Some of you must have had this problem at high mileage. What was the fix ?