2015 Sonic 1.4
127,000 miles
Automatic
Purchased non running, suspecting that cylinder head was damaged. Zero history was known by owner (car flipper I assume).
Compression test showed 2 cylinders at 70 PSI and 2 at 120.
As I started the repair, I quickly learned an attempt was already made to repair this engine. Missing bolts, new head gasket, timing chain, etc.
Replaced cylinder head with complete GM unit. All new gaskets, head bolts, timing chain and plugs. Engine started right up and runs great. New issue was the smoke out of tail pipe. BBQ amount of smoke.
Inspected intake manifold and found PCV valve missing. Replaced with GM unit. Still smoked.
Read on this forum that valve cover/ PCV is known issue also. Replaced with the updated Dorman unit. Still smoked.
Looked at the PCV pipe installed on the engine and determined that it was not for this vehicle. Replaced with proper unit. Still smoked.
Turbocharger and manifold were inspected while off and I saw no signs of damaged, so I reused. After all the above repairs, I figured it may actually have been bad. So I replaced turbo and manifold including wastegate. Still smoked.
I decided the exhaust system and or intercooler could have oil build up from all the issues in past. I took the Sonic out for a "spirited" test drive. I had a blast in this little go-cart! What a fun car. After several miles the smoke lessened then seemed (from mirrors) to be gone. I returned to garage and let idle. No smoke... at first, then slowly increased to same amount.
Removed pipe at throttle body and oil was present. I then removed front bumper and all hoses/pipes from turbo to throttle body and cleaned them out as well as the intercooler. Smoked on start up. Took out for drive, cleared up again until idle for awhile then smoke returns.
I removed exhaust after cat/con and started again to see if was possibly had leftover oil in exhaust system. Smoke present at exit of cat.
Throttle body dry since cleaning.
Car runs so well that all readiness monitors have reset. No DTCs. Starts, runs and drives perfectly. So I cannot believe it has a broken ring. Leak down test on all 4 cylinders as well as compression is good.
Turbo/manifold kit is aftermarket. I guess chance its bad out of the box. I will remove the cat/con from turbo in morning and start it and see if its leaking oil and cat is baking it to cause the BBQ effect out tailpipe.
Have any of you experienced this? How would you go about diagnosing it? The fact that I do not see any DTCs or knock sensor retarding timing, leads me to believe that oil is not being "combusted".
127,000 miles
Automatic
Purchased non running, suspecting that cylinder head was damaged. Zero history was known by owner (car flipper I assume).
Compression test showed 2 cylinders at 70 PSI and 2 at 120.
As I started the repair, I quickly learned an attempt was already made to repair this engine. Missing bolts, new head gasket, timing chain, etc.
Replaced cylinder head with complete GM unit. All new gaskets, head bolts, timing chain and plugs. Engine started right up and runs great. New issue was the smoke out of tail pipe. BBQ amount of smoke.
Inspected intake manifold and found PCV valve missing. Replaced with GM unit. Still smoked.
Read on this forum that valve cover/ PCV is known issue also. Replaced with the updated Dorman unit. Still smoked.
Looked at the PCV pipe installed on the engine and determined that it was not for this vehicle. Replaced with proper unit. Still smoked.
Turbocharger and manifold were inspected while off and I saw no signs of damaged, so I reused. After all the above repairs, I figured it may actually have been bad. So I replaced turbo and manifold including wastegate. Still smoked.
I decided the exhaust system and or intercooler could have oil build up from all the issues in past. I took the Sonic out for a "spirited" test drive. I had a blast in this little go-cart! What a fun car. After several miles the smoke lessened then seemed (from mirrors) to be gone. I returned to garage and let idle. No smoke... at first, then slowly increased to same amount.
Removed pipe at throttle body and oil was present. I then removed front bumper and all hoses/pipes from turbo to throttle body and cleaned them out as well as the intercooler. Smoked on start up. Took out for drive, cleared up again until idle for awhile then smoke returns.
I removed exhaust after cat/con and started again to see if was possibly had leftover oil in exhaust system. Smoke present at exit of cat.
Throttle body dry since cleaning.
Car runs so well that all readiness monitors have reset. No DTCs. Starts, runs and drives perfectly. So I cannot believe it has a broken ring. Leak down test on all 4 cylinders as well as compression is good.
Turbo/manifold kit is aftermarket. I guess chance its bad out of the box. I will remove the cat/con from turbo in morning and start it and see if its leaking oil and cat is baking it to cause the BBQ effect out tailpipe.
Have any of you experienced this? How would you go about diagnosing it? The fact that I do not see any DTCs or knock sensor retarding timing, leads me to believe that oil is not being "combusted".
