I recently purchased a 2003 Hummer H2, which has been sitting up for a couple of years now. I am far from a mechanic, but I can tell there a few things which need to be addressed.
First off, on a cold start, it will puff out a white/blue smoke. Most would say this would be valves or rings bad correct? This hummer has 145k miles on it. I flushed fluids, new oil filter and fuel filter. Any suggestions?
Thanks!

 

Valve stem seals?
Do the trunnion swap while you are at it.
http://www.summitracing.com/parts/cc...-kit/overview/

 

Do a compression test to see if the rings are warn or stuck. You can also do a leakdown test, this test would determine if your valves OR rings are not sealing.

 

Valve stem seals more than likely. If it had bad rings, it typically would smoke on acceleration.

Tim

 

Yeah I second getting a compression test done. Hopefully you got this Hummer for cheap with it having problems. Let us know what you find.

 

Funny thing, just Went through this with a buddy at work. He bought a used low mile Chrysler 300 and brought in for a full service. After the service it started smoking on start up each morning. We then dropped a quart of oil out and added a quart of Gunk MF3 High Mileage cleaner. Let it idle in the driveway for a hour, dumped the oil again and man was it a mess. Ran some new oil for a day and did a change again. Conclusion is that the previous owner never changed the oil and the engine was gunked up beyond belief. Week later all is good, no smoke.