beaker53

hey guys, i know there are hundreds of posts relating to the ever so general "chevy rough idle" thing, and now unfortunately, this has happened to me. however, i have many details at my disposal, and i will be very specific to avoid confusion, any help is appreciated.. so PLEASE READ ON.

THE PROBLEM:

-the truck has an extremely rough idle whether it is warm or cold, and the brightness of the lights on the dash fluctuates with the small changes in rpm the rough idle produces.

-while cruising on the highway, and especially up hills, although not when the rpm is over 3000, it feels as though the torque converter is slipping, although it is NOT. the truck will lose power for a fraction of a second, and then continue as if nothing happened. if you weren't looking for this, you would not feel it, it is that slight.

-i pulled a code from the computer after this happened the first time, and it is the only code the computer has produced.

freeze frame of code P0300 (RANDOM/MULTIPLE CYLINDER MISFIRE)

Vehicle VIN: 2GTEC19T031221705
Vehicle Manufacturer: GM
Vehicle Calibration ID: 12579405
12577861
1257

Freeze frame information:
------------------
Engine Load = 5.098 %
Engine Coolant Temperature = 3 °C
Fuel Trim Bank 1 Short Term = 0.781 %
Fuel Trim Bank 1 Long Term = -3.906 %
Fuel Trim Bank 2 Short Term = 0.781 %
Fuel Trim Bank 2 Long Term = -3.906 %
Intake Manifold Pressure = 7.107 psi
Engine RPM = 789.25 rpm
Speed (OBD) = 0 km/h
Mass Air Flow Rate = 12.17 g/s
Throttle Position(Manifold) = 14.118 %

End of report.

I have also changed my fuel filter, oil+filter, air filter, spark plugs, battery, and alternator since pulling the P0300 code.

Any help you guys could give me would be great, as i know you are GM gods haha, if you have any further questions on the issue, i will answer to the best of my ability, hopefully we can solve this, thanks.

LS1MCSS

iTrader: (18)

3 degree Celsius = 37.4 degree Fahrenheit. Is that temperature correct?

parks450

iTrader: (17)

coolant temp is way off, kinda sounds like a coolant temp sensor problem. Is it hard starting?

AllGo'N'Show

Coolant temp definitely looks off, I know it gets cold up here in Alberta but if you were driving up a hill when you got the CEL your temp should be above 3c by then, unless this was immediately after a cold start?

beaker53

i live in alberta, that was immediately following a cold start. i was thinking it might be a vacuum leak somewhere, but i do not know the proper vacuum pressure at idle for this truck.. and i dont really wanna go spraying ether or tb cleaner everywhere.

beaker53

to clarify, i was letting the truck warm up, and i came back to a CEL.

AllGo'N'Show

Did you change plug wires with your plugs? Factory wires have the junkiest connectors I have seen yet, mine were rusty to crap inside and I believe they fixed my main misfire, now i am chasing little ones.

GMRL

Its common for the intake gaskets to leak on gen 3 truck engines.
Check the fuel trims in closed loop, if they're higher than 10 to 15 that might be it.
Try spraying some ether at the base of the runners and see if the idle changes or th trims go negative

spiro27

first thing do a compresson test. so you can verify if its a mechanical prob.