Hi there, my main question is: What could be the cause of oil inside intake system (all the pipes starting from Y-pipe, intercooler piping, intake elbow etc.)? There is quite a bit of it, all the walls are soaked and if you rotate the pipe a drop or two of oil will drain, so it's literally sitting in there in liquid form.

Setup: RX7 FD, 99', JDM, stock twin turbos, Apexi Power FC base map

Longer story: So my car is not really reliable after engine swap, one of the issues that came up recently is that when I started engine braking (I was driving slowly trying to match someone else's car speed, hit low rpms like 1500-1600), the car started backfiring, so I jumped onto throttle again and it kinda fixed itself. I wasn't too worried, but after few days the issue came back, again, I immediately reacted with some throttle and after few seconds on weird noises and backfires it fixed itself again. On next day, the backfire incident started to occur quite often, to the point that even on idle it was backfiring, kinda sounded like running on one rotor (I blew one motor in the past (lost compression), this sounded slightly different, but it was very similar (I was so scared...)). I was away in the city, so I was worried what to do, I was like 20% sure the motor was blown, but I remembered that this issue was fixing itself in the past so I decided to drive back home (5km), and sure enough, after a few minutes of driving it fixed itself and car regained power, I made sure to be in low gears on high rpms and drove home safely. Finally, here we are now - I decided to check the spark plugs and while at it, replace them, and it turns out they were quite dark, probably running rich, but one spark plug, specifically front rotor trailing one, turned out to be oily on the threads and even on the tip. Changing the spark plugs to brand new ones fixed the problem, I drove the car for two days and the issue didnt come back yet. Therefore, my conclusion is that excess oil gets into my plugs, clogging them up, and it stops firing and creates backfires. Is my assumption correct? If so, how would you proceed, I guess I should stop premixing to reduce the amount of oil, but more importantly, maybe I should do something about the intake oiling - how does it get here? From turbos?

I appreciate any help and advice I can get, looking forward to hearing from you

 

Both are normal

First, the stock PCV system vents oil back into the primary turbo inlet. That sucks up oil vapor and sometimes gets oil sloshed into it when doing an oil change. That will then coat the intake tract. I've done a few posts on my catch can setup, this will solve that problem. But, in general, while it's messy, that's how the car was designed stock. It's not ideal but it isn't the worst thing.

Second, don't drive your car under 2000 RPM. This is a rotary not a Chevy big block. You are lugging the car big time at those RPM's and the car isn't going to run well or be smooth. Always cruise at 2000 RPM or higher and you will be fine.

Dale

 

I've been driving at low speeds and low throttle with RPM's as low as 1600 ever since I bought it in 1992 w/o issues. I do stay over 2500 for heavier-throttle acceleration and give it an "Italian tune-up" at least once every time I drive it. It runs perfectly under those conditions. YMMV.

 

Thanks for the reply Dale, the thing is, I already have an oil catch can and while I can understand oil in the intake system is normal, I don't think backfiring and soaked in oil spark plugs are normal?

Also, I always drive over 2000 rpm. Tbh, I don't even try going under 2500. This was a one time incident, I don't think it was normal that the issue happened just because of it.

 

Can you drive under 2000 RPM? Yes. It will have no power, jerk and buck when you try to accelerate, and just act a fool. IMHO no good reason to do so.

Clean up your intake tract and see if the oil mess comes back. How is your catch can set up? Again look up my setup, that's a great basic catch can setup.

Just re-read your first post, to be honest I didn't read it well/fully the first time . That case does sound like you fouled out plugs. Also do you have the stock OMP and are also premixing? How much are you premixing?

Dale

 

Yes I have the OMP, but I'm not sure if it works, I guess it should? So just to be sure, I also premix, 40ml (1,35 oz) of two stroke oil per 10l of gasoline (2.62 gallons? Idk imperial, excuse me for metric system ).
Perhaps it's too much oil? I'll try to verify if OMP works and if it does, I'll stop premixing, or you have other ideas?

 

I had lots of oil in the intake when I first got my FD. Enough that after a long drive I had oil pooling in the intercooler. My issue turned out to be turbo blowing oil into the intake. I agree with the clean up and see. But also check both sides of the intercooler for oil.

 

Without running the numbers your premix ratio with a working OMP looks about right. (0.5 oz @ gallon is generally accepted here)

I have always had SOME oil in the intake track but never felt the need for a catch can. Oil is getting a little heavier the last couple years. Maybe I’m just hurrying those oil changes, but then I’ve got about 135,000 miles on the original turbos too.
And even with a lightened FW I can drive at low speed and rpm on the occasion that I do need to, and never felt like my car…or I were acting a fool.
Once a year in the spring I pull the IC and clean it. A little degreaser or just heavy solution of dish soap and hot water in a utility sink. Let it sit for a few minutes, rinse thoroughly.

Your bucking and misfire issue may just be cumulative over time. I’d clean the IC and hoses, replace the spark plugs and maybe even pull and clean the IAT. Then just check both the intake track and plugs after a few thousand kilometers before worrying too much.