Sudden oil burning issues, I'm at a loss.

[86Shelby]

The car is a '91 Nissan Sentra, 1.6L with 17x,000 miles. 48 hours after doing some work to it the engine starts burning oil like mad.

I spent Friday resealing the lower timing chain cover. This involved pulling the valve cover, oil pan and obviously the lower front cover. I did not mess with the timing chains, valve train or rotating assembly. A new valve cover gasket was installed. The top edge of the cover is a pain to get to seal 100% since it slides in parallell to the cylinder head and only RTV is there to seal it. It's not my first time at the rodeo with this engine.

Once I was done with the job I took it down to the carwash to clean up the engine bay since a lot of it was covered in grease and to help see if it starts leaking again. No leakeage, which is good. After the bath there is a misfire only at moderate to heavy loads, I figured water was shorting out the ignition which it was. Some water got into the plug wells, after drying out no more misfire. The owner takes the car and all is well.

Today he commented that the car had a huge cloud of white/blue smoke when it was started this morning and it did it every time he left from a stop. So I check it out after work and sure enough a small puff of blue at startup, and some smoke whenever the engine was accelerating; both free revving and under load. I found a plug wire not 100% seated and snapped it into place. It stopped smoking almost instantly. 15 minutes later the owner leaves with not a whiff of smoke.

3 miles down the road I pass him as he's turning left and there is a HUGE cloud of blue smoke behind the car. I know I'll be hearing about this in the morning. The oil leve is right at the full mark. The engine hasn't been treated to normal oil changes as everything is a redish carmel color but no visible buildup. What could cause something like this? I'm out of ideas. It didn't smoke before I worked on it and it stopped for a while this evening. The engine runs great, nice and smooth but now blows smoke like a mofo. Any ideas you have are appreciated.

[MR. X]

Leakdown and compression test results?

[mark]

does the pvc valve go into the VC? didnt put it back in backwards?

[86Shelby]

I don't have access to a leakdown tester, but may be able to borrow a compression tester.

I only unhooked the vacuum line to the PCV valve to remove the valve cover, it did not get removed from the VC at any time. Sprayed the inside of the VC with brakecleaner to remove the oil inside right before installing it.

[onerippinturbo2]

sounds like the pcv is clogged up, spraying that brake cleaner in there may have clogged the valve. worth a look.

[MR. X]

My thoughts.

[turbovanman²]

Its possible that the vc baffles are full of carbon due to the lack of oil changes and you cleaning it disturbed that crap and the PCV system can't work now.

[86Shelby]

Sounds reasonable. I'll see if I can get the car overnight and check it out.

[86Shelby]

Found the problem and it runs just fine now, with no smoke! The PCV draws air from the crankcase, through a passage in the head that seals to the valve cover. The old rubber grommet/seal had seen better days and allowed a ton of oil past it. A little RTV with some curing time and it's all good.