i8acobra

New member here. Joined just to ask this question as I myself don't actually own an RX8. I have a shop and am building an SCCA T4 car for a client. It's an '11 Series II car.

First, some background about me... I've been building and working on cars for over 25 years. I mostly specialize in Nissan and GM products. This is the second RX8 I'm building. I know quite a bit about engines in general, but am a total noob when it comes to rotaries. I'm ASE and Nissan SCOPE certified.

Second, some background about the car... It came to me from another shop. It's having an issue with dumping massive amounts of oil into the engine and the other shop couldn't figure it out. They changed the engine twice, thinking there was an internal engine problem. When I got the car, the engine was mostly removed. The car was a salvaged flood car.

First thing I did when I got the car was to drop the entire drivetrain out the bottom to do a full inspection. Other than the engine issues, I didn't find anything major wrong with the car. I installed a salvage yard engine that was sent with the car. Everything on the engine is stock, down to the OEM air filter because it's a T4 class car. When I started it, it started having the same issue, dumping very black oil out the exhaust manifold. The engine has brand new oil in it, so the oil must be getting dumped in to the rotor housings and partially burned. That's why it comes out black. Also, the brand new plugs are oil fouled.

This is a different engine than was in it when I got it. The oil metering system came with this engine, so it's not a mechanical issue with the metering system as none of the components that were in it when I got it are still there.

So, here's my question... Could a harness or PCM fault cause the metering system to be commanded to dump way too much oil or stick wide open? I'm about ready to make a bypass hose to bypass the oil metering system completely to run the engine and hopefully get all of the oil out of it. Since this is a T4 class car though, I can't leave it bypassed. There are also several low circuit voltage codes stored for several systems. I'm thinking about swapping out the PCM.

I'd really appreciate any help from the resident engine gurus here.

i8acobra

OK... Some follow up info. I removed the intake plenum and made a bypass hose to run oil directly from the feed port behind the coils up to the return port on oil filler neck. I left both solenoids plugged in and also left what looks like a pressure sensor on the second solenoid plugged in. Put everything back together and fired it up. It's been running for 20 minutes now and there's no longer any smoke at idle and very little when I rev it. Also, no more misfire, so the plugs have cleaned up.

My question now is, has anyone else experienced anything like this? Did you have a bad PCM? With this being a flood car, and having multiple low circuit voltage codes, I'm leaning towards PCM, rather than a harness issue. I suppose it's possible I have multiple plugs with corrosion, which would also cause high resistance and throw low voltage codes...

Thought? Anyone?

9krpmrx8

iTrader: (46)

Feed port behind the coils? Do you mean the vacuum hose from the oil metering vacuum distribution block located on the red injectors that connects to the intake? What year RX-8 is this? Low voltage codes to what?

There is a TSB for excessive OMP injection IIRC.

i8acobra

It's a 2011... Second gen. It has an oil feed line that exits the engine behind the coils, goes to the first oil injection solenoid, then to the second, then returns the excess oil to the oil filler tube. Black hoses with yellow locking tabs.

The low voltage codes are for O2 sensor 1, O2 sensor 2, SSV valve, evap circuit, secondary air pump, and a few others. Also the low oil level light is flashing and the radiator light is on. The key light is also on. The engine ground is good.

I have AllData at the shop, I'll check for a TSB.

9krpmrx8

iTrader: (46)

Ah.....That explains it.

I would check voltage at the ECU. Also check www.normalexception.net, you can get the S2 FSM and electrical diagrams there.

i8acobra

Yep. My next steps are checking reference voltages on each circuit at the PCM. I've got AllData at the shop, so I have access to all manufacturer's service manuals, as well as TSB's and recalls.

i8acobra

Found part of my problem... EGI 2 fuse was partially blown. It looked blown, but there was continuity across it at high resistance. Replaced the fuse and the codes are gone. Haven't tried removing the oil injection bypass yet. I'm still wondering why Mazda would have the solenoids default full open, drowning the engine in oil, when voltage is lost at the solenoids.

ZiG

I'd have to think they would prefer that over starving the engine of oil?

i8acobra

It would actually be preferred that a check engine light illuminate and put the engine into limp mode. At low rpm, these engines will run just fine without oil injection for long enough to get the codes read and get the car serviced.