Hello. I've been trying to determine why my dads truck is burning oil. It's a 2006 hummer h3 model. I've noticed a lot of oil residue covering the drive shaft in the front when I changed the oil last so I know it's leaking somewhere. It usually blows white smoke out of the exhaust pipe during startup but after that it doesn't smoke at all. The engine runs smoothly sometimes but other times it kinda runs rough. I believe the fuel injectors could be bad which is leading to the misfiring. Also could bad fuel injectors cause the oil to burn?? Or maybe a seal that is dry rotted somewhere?? It has approximately 180 k miles on it. Any help would be much appreciated. Thanks!

 

Finding an oil leak would require you to clean the underside as good as possible and then see if you can determine where/what area the leak is coming from. As far as running rough, start with cleaning the MAF and throttle body. If it doesn't improve you may need to do a compression check. Are there any error codes?

 

Running rough and misfiring are different issues in my book.

Just like burning and leaking oil are separate issues. Sure they can be happening at the same time, but worn rings do not cause a leak per se, unless blow-by is so substantial that you are increasing block pressure, which would throw a code? If the rings are worn, well.... you can try some NO Smoke.

It would be highly unusual for a dirty injector issue to create a misfire. Misfires are ignition or electronic related, not fuel system.

With that kind of mileage, has anybody ever cleaned the MAF or Throttle Body. Clean those and use only MAF and TB cleaner, then see if that improves the situation.

Next up, compression check.

 

I'm gonna suggest that you clean the MAF, TB and check to make certain that the hose under the resonator box is not missing or dry rotted.
Also the rear of the rocker cover could be leaking. The oil change was done sloppy. The oil pan is leaking. The trans pan is leaking. Etc. Agreed clean everything good and start from square 1.