I have a 93 Chevy c1500 with a 4.3L and a 5-speed manual transmission with around 188k miles. Been in the family since new... What could be causing a single puff of smoke only at a cold start up? If I turn the truck off then back on, no smoke. However, wait about an hour then starting it back up, it will have a single puff of smoke and goes away immediately. Things I have done to try to fix it, rebuilt throttle body minus IAC, replaced egr, pcv, throttle position sensor, distributor cap, rotor, spark plugs and wires. Also coolant level is always full and doesn't burn much oil between seasonal oil changes. Truck runs pretty great otherwise. Any help will be greatly appreciated! Thanks.
Hi, kesterpaul62. I appreciate the idea. I just completed the test and fortunately no blown head gasket! The test liquid remained the same color. I have just ordered a map sensor being that its 30 years old. Not sure if that will do anything but shouldn't hurt. Additionally, I read in a comment section on youtube that stated oil could possibly pool up near the PCV value on a newer chevy truck. Maybe its getting sucked into the tbi through there on startup? I Haven't pull the valve covers off yet to see if that's the case. Was waiting on this combustion test. Any other ideas would be greatly appreciated.
What color is the smoke? If it is white, it suggests coolant got into the combustion process. If it's blue-ish, it could be oil getting in a cylinder. If it's blackish, that would imply too much fuel being burned. Something you could try is get a bore scope, remove the spark plugs, inspect the inside of each cylinder and their piston and valves and note the coloration. If one is different from the other 5, that might be where the problem is originating.
perfectly normal for an engine of that age. As long as the smoke goes away I wouldn't worry about it
