Hey all, just wanted to get anyone's thoughts that would be happy to share on a situation I'm in. I'm trying to figure out best next steps.

History: I have an '02 that I blew a stock VVT motor by accidentally having it in gear while towing with the rear wheels down. After it happened, the car would start, but billowed smoke out. While changing the oil after it, everything seemed soaked in it. There was oil leaking out of the seams between the pipes on the exhaust for example.

Today: Found a great deal on a built non-VVT motor. Got it swapped in over the last few weeks, cleaned everything I could. Let the exhaust sit outside to try to drain anything in it. Its in and running on the same base map I had before. It starts and runs beautifully on my previous tune, except, after the car warms up and starting under load, it will billow out white white/blue smoke. It doesn't do it during warm up at all at least that I can see. After driving for 3 to 5 minutes, it will heavily smoke. I'm not sure whats causing the smoke. The guy I bought the motor off of says it was perfect days before he pulled it and sent me a dyno video to show it (he had it dyno'd a few days before he decided he was done with it). I'm left with trying to diagnose what is causing the smoke. Here are my thoughts, feel free to add:

1. The high flow cat I have is fouled with old oil. Once it gets up to temperature and then with hot exhaust (under load) it is still burning old oil out of itself and will eventually stop. Or this is true and it will never stop?
2. A friend mentioned I may have blown the oil seals on the efr turbo I have. While the oil did get over done (read 290F on my gauge after I figured out what was happening), my other seals visually looked fine on the motor and I even reused a few on this motor that fit since this one wasn't using OEM seals.
3. This built engine actually is blown and the guy selling it to me wasn't truthful (i doubt this, he actually works for a very reputable local miata shop).

About the only thing I can think to do to eliminate some of the possibilites above is to drop the exhaust and run it open downpipe. If there's still this billowing smoke after everything gets hot, then I know at least its not the cat/exhaust. If it works out, then I can get the cat replaced. If the system still billows out smoke, thoughts on my next steps? I suppose I could try to borrow my friends stock header/exhaust and see if the smoke goes away while using that? If it does it is clearly something with the turbo. Anything easier that doing these swaps like this? Thanks!

 

Check the engine oil level, if it's not losing a bunch, you could just drive it/beat on it, and see if the problem goes away. That would be the easiest I can think of. If it doesn't go away, then follow the plan you wrote out to try and eliminate the cause.

 

I dig it! Oil level hasn't seemed to change almost at all.

 

Probably late to the party here, but I change out a lot of catalytic converters/exhaust components at work. As would be expected, many of the components are usually rusted together or at least dirty enough that liberal amounts of penetrating oil are needed to get the fasteners off.

A small amount of penetrant applied to a set of exhaust studs/bolts/nuts can create way more smoke than you'd expect it to. Same goes for actual oil. How many miles have you put on the engine/car so far after the replacement? If your exhaust and cat were harboring a notable amount of oil, it might take over a couple dozen miles to burn most of it off.

Interested to see where this leads for ya.