2001 Chevy Suburban V8 Four Wheel Drive Automatic 110000 miles
Our Suburban will start fine, but after about 15 seconds or so it starts a very rough idle and will die out. I need to try and hold the RPMs at about 1200-1500 until it warms up a bit and then it runs fine. This happens when temperatures go below 20 degrees. Truck has been tuned up (plugs, wires, fuel filter). Fuel pressure was checked and no regulator or fuel pump issue. A code 300 will show up from time to time, but " random misfire" doesn't help much. I sprayed carb cleaner around the intake manifold and did not experience any RPM fluctuations thinking manifold leak. What do you think might be causing this?
Update today, friendly service station held onto the truck while I was at work and was able to duplicate the misfires at cold start up. It misfires at cylinders 1 and 3 until motor reaches about 130 degrees. They have seen this before on this motor and the 6 liter motor and suggested having the Chevy run the diagnostics on it. After reaching a warmer temperature engine ran fine.