I’m on a stock rx7 FD that’s had most of its stuff refreshed such as vacuum lines. I have an apexi ecu installed with a tune from fc tweak. Everything should be in working order however I noticed blue smoke (oil) from my exhaust only at idle and a lot of it. When I’m at a red light, it almost looks like a burnout.

as a result, I checked my PCV valve and it was clogged so I threw it in some gasoline and hooked it back up and a few days later I check and it’s clogged again. I repeat the process and today I checked and it’s clogged. It’s not completely clogged each time but definitely not as free moving as it should be after the gasoline treatment.

so what does this mean? Excessive crankcase pressure? I have a 1st gen HKS BOV. Could that be causing the issue? Not sure what else. Turbos look fine. I took off the elbow to the primary and the blades spin freely with no play and there’s no oil residue there either.

could it be my tune? I doubt a tune could cause clogged PCV valves and Xavier’s fctweak software is very good.

I have 02 feedback disabled in the apexi and a wideband installed.

im thinking of just getting a catch can as that would help relieve the crankcase pressure no?

also to test crank case pressure I can get a rubber glove and put it over the top of the oil fill neck to see if it inflates (indicating excessive pressure) right?

 

Maybe..... replace it?

You can also unplug the omp and rule that out. Excessive crank pressure at idle isn't really a thing unless something is really really wrong. Oil control ring failure is a possibility but so is a lot of other things. Burning oil at a high enough rate to cause the smoke you're describing is a problem.

You don't actually need the pcv valve at all. For the sake of testing, just leave that nipple open on the oil neck and cap the pcv port and see if it makes a difference. Keep in mind if there's a lot oil in the exhaust then the change won't be immediate. The residual will need to burn off before the smoke stops

 

ok so leave the pcv valve nipple on the oil fill neck open to atmosphere and cap the port on the side of the UIM?

also yeah I thought about replacing it but mechanically it’s a simple thing that should work like brand new if it gets cleared up with gasoline no?

I don’t know if it’s excessive crankcase pressure for sure but I assumed that because my pcv valve is usually oily when I pull it out and clogged up or in the process of getting clogged. That indicates oil must be rising through the oil fill neck and into the pcv valve to go into the UIM correct? Some of it should be going into the turbos as well no? Well it should be going there before the PCV valve.

also when I do pulls or drive normally I get no smoke. It really only happens at idle when I’m at a red light. It’s embarrassing at this point I feel bad for anyone next to me with their windows down

ill look into disabling OMP and seeing if that helps after I try the vent to atmosphere trick

 

the oil change place overfilled mine last time, and i had the same symptom. so that is a possibility too
also the 1995+ cars got rid of the PCV valve and only use the hose that goes from the oil filler to the front of the turbo, so that is an option

 

so capping off the pcv nipple and just keeping the one on the bottom that goes to the primary turbo is what the 95+ specs do? Wouldn’t that cause pressurization of the crankcase by not having a pcv valve? Also, when people install a catch can, they cap off the pcv valve nipples on the oil fill neck and UIM and run a catch can between the second nipple on the oil fill neck and the first turbo right? But the catch can has a breather so that it doesn’t pressurize the crankcase?

 

Oh wait, crankcase is only pressurized if it’s attached to the UIM without a pcv valve. If it’s not attached to the UIM whatsoever, there’s no way it can get pressurized afaik correct?

 

So to remove the PCV valve and use a catch can I have to

1.cap off both the top nipple on the oil fill neck and the UIM nipple.

2. cap off the second (bottom) nipple on the primary turbo elbow

3. Run a hose from the bottom nipple on the oil fill neck to a beer can or a vented catch can

is this correct?

or do I have to run a hose from the bottom nipple on the oil fill neck to a catch can and then from the catch can to the bottom nipple on the primary turbo elbow?

 

You don't need a catch can. It's not going to do anything. A proper install is beyond what you're describing for it to be any kind of effective. Troubleshoot doing what has been suggested to find what your problem could be. Engine failure is on the table so work through the process to determine the cause.

Catch cans are not solutions on stock FDs for anything

 

ok but to test if my pcv valve is the issue I can simply plug the pcv nipple on the UIM, and leave the top nipple on the oil fill neck vented to atmosphere? If smoking stops then it’s PCV valve, if it continues, it’s probably a bad sign of engine failure coming