Engine Performance problem
1999 GMC Sonoma 4 cyl Two Wheel Drive Automatic 200000 miles
Recently replaced head gasket and had cylinder head machined down (was warped). Also recently replaced radiator, thermostat, water pump, and lower radiator hose.
Everything was running great for a few weeks after replacing the head gasket and radiator (along with lower hose). Then one day it starting running very sluggish until you drive down the road for a ways (maybe 3-4 miles), then runs just fine. Maybe still a bit sluggish at idle. The most likely scenario I came up with was contaminated fuel. Ran fuel injector cleaner through each tank (currently on my 4th tank of fuel since then), still running sluggish on intial startup until warmed up. DTC code was reading several hundred instances of cylinder 2 misfire, along with a few (5-10 misfires or so) on each of the other cylinders. The engine requires you to hold down the gas pedal in order to start it up in the morning. Then runs sluggish for awhile, randomly "catching" more power intermittently. Possible air seepage somewhere around intake. Not 100%positive on that though. Vacuum line? Can't be spark plugs (changed those with head gasket).
Not sure if this is related but the turck also operates at appropriate temperature (190-210) for the first 10 minutes of driving or so, then the temperature guage drops to less than 100. Also I have NO HEAT. Brrrrr. I live in Michigan! Recently replaced radiator, coolant, lower radiator hose, thermostat, and water pump. Did a backflush of the heater core today and everything flows fine, except when engine is warm, only the inlet heater hose is hot. Outlet is cold. Backflush and forward flush with garden hose and adapter showed free flowing passage.
What is causing my lack of heat, and why might I be misfiring on cylinder 2? I'll take all possibilities here.
Also, tested Engine Coolant Temperature sensor, works perfectly. New thermostat stuck open? I am completely overwhelmed here. Please HELP!
have the same problem?
Thursday, October 23rd, 2008 AT 3:20 PM