Smoking only at idle
 

Hi everyone, so my 2005 RX8 has a freshly rebuilt motor, all stock. Every seal was replaced and measured to to specific tolerances.

Since the motor rebuild, we've had a unique problem - smoking only at idle when you blip the throttle. No smoke on startup, no smoke during high revs (we autocross the car), no smoke while driving. However, let the car idle for a few minutes, blip the throttle, and it will smoke you out. Blip it a few more times and it will clear out. Shut it off when you come to a stop, and it won't smoke. This seems to be unique to idle only.

We added a catch can to the line between the oil fill port and the service ports (we did the milky dipstick tsb at the same time as the motor rebuild, which rerouted the line between the oil fill port and the accordian to between the oil fill port and the service ports - along with a few other lines that were rerouted). There is no oil coming through this line, and the car still smokes like crazy when you blip the throttle after idling.

We checked the lines going into the intake accordion - no significant oil.

We are looking for ideas of where to look next or what to check.

Possible oil control ring springs installed upside down?
Were endplates honed?

We are fairly certain the oil control ring springs were installed correctly. We followed the FSM exactly. We realized we had mixed up the "front" and "rear" direction of a rotor at one point when we went to install it on the eccentric shaft, so we went back and moved the springs so they would be on the correct face. We were paying pretty close attention to that step, but of course anything is possible.

With that though, wouldn't the car also smoke on startup after sitting overnight, and also at high RPM? We don't have either of those symptoms.

End plates were honed but not excessively. Just enough to get a dull finish. They were also well within spec according to the FSM.

Yeh sorry I dont know, I haven built an engine since 1998, but i once built up a 13b bridgeport, it smoked a lot at idle, and on the over run , thought i may have put them in upsude diwn so after about 500 ks and no improvement, pulled down and sure enough,.
Seems most people on here dint buikd thier own engines, maybe @brettus could help

We are still narrowing down options. The newly installed catch can on the hose coming out of the oil fill port is not capturing any oil, indicating no blow by, even after an autocross we went to.

We performed the FSM resistance checks on the OMP connectors, and they all passed. Could the OMP pass the resistance checks yet still need to be adjusted possibly?

We tried premixing and unplugging the OMP, but the car still smoked after idling. Didn't pull any CEL's or go into limp mode (didn't drive around though). Would someone please confirm that simply unplugging the OMP will shut it off so this is a valid test?

Car is still only smoking at idle - not at high rpm or startup.

We pulled the plugs and both are slightly oily.

Next up we are going to check the oil pressure to make sure it isn't really high at idle or something.

Anyone have any other ideas?

BTW, got the car dyno'd and it's making 25whp and 10wtq more than before the rebuild! Gains all across the rev range.

Are you 100% sure that you are burning oil and not coolant? didn't see you specify a color of the smoke
White smoke is coolant, blue smoke is oil.

Definitely oil - it's blue, and smells like oil.


One other thing to mention in case it is relevant, is that the car doesn't do the smoke at idle thing when cold. Once warmed (10 minutes ish) up then any idling over 3 minutes (ish) will cause a puff of smoke if you blip the throttle. Longer idles will cause a mega smoke show once you blip the throttle.

What all was replaced when the rebuilt engine was put in?
I'm assuming you still have a cat since you said it was all stock? Hows the cats health if applicable
Hows the ignition health?
Hows the oil consumption about a quart every 1000 miles?
Does the engine bay smell like oil?
Does the catch can have a one way check valve that was put in the wrong way?

Edit:

Also has the reman engine been broken in properly?

Thanks sonicsdaman - I'll try to answer your questions below. Let me know if you have any other ideas of things to check!


Pretty much everything was replaced - 100% new seals. Everything listed as recommended on the Mazda Motorsports parts list here
In addition to the list above, we also put in new rotor housings, new SSV, new OMP lines, 3 new oil nozzles (one checked in spec, 3 failed by the vacuum test), thermo pellet, and then the ventilation kit (reroutes vacuum lines). During assembly everything was measured carefully - side seals to 2 thou clearance, etc. We followed the manual carefully and performed the FSM recommended checks on everything along the way (thus why we replaced the oil nozzles). Re-used the existing bearings as they were in spec.

Cat was replaced with a low mileage one in good condition at the same time as the engine.

Ignition health is good. Have the upgraded 14 tooth starter, Bennetbuilt coils and wires, and fresh plugs (removed and cleaned recently). Also have the Optima Red Top battery.

Oil consumption is greater than a quart per 1000 miles, but the car is autocrossed heavily every weekend so not sure if that's a good indicator to go by. At the last event, dual driving, we got around 24 runs in (timed runs + fun runs at the end) and the car used a 1/2 quart. I was co-driving with another RX8 owner and he said that was similar to what his car usually uses.

The engine now has around 1400 miles on it now. We took it easy on it the first 500 miles (lots of accelerating/decelerating and no high rpm, along with multiple oil changes). Also, this idle smoking issue has been present since day 1.

Engine bay does not smell like oil and there are no leaks.

Catch can made no difference and there is no check valve. We put it in the middle of the line going between the oil fill port and the two service ports on the LIM (this is an S1 but the ventilation kit rerouted the lines similar to an S2). It is not capturing any oil, and the lines are dry, indicating no high rpm blow by.

BUMP! my car is doing the EXACT same thing. did this ever get resolved? i cant figure this one out for the life of me right now.

No, but over the past 5 autocross seasons the car has smoked less and is making more and more compression and power.... still holding steady at 125+psi. So, I stopped worrying about it.

Thank you for the reply, much appreciated! Hopefully mine will diminish as well, if I find a solution I will update here

Mine did much the same as Tamra's, smoky at idle and as I've gotten mileage on the car it's gone away. ~6k street miles, 150+ autocross runs, and four track days in the last year and it only smokes a little bit if I mix 1 Oz/gal on premix.

Hi,

So did you have any update to this?

Seb.

I haven't had any official solutions. Still driving the car and topping it up as needed but after my investigation I'm pretty sure it's an oil control ring issue I don't see what else can cause it. I hope someone here can prove me wrong though

thanks for your reply! ;)

how many miles/km did you drove like this?

No problem! It's been about 1000km so far, I don't drive my 8 that much. It's pretty annoying so I bought another engine to rebuild and swap them out in the spring, but if I don't get around to building it I know I can still drive the car

Ok,
I've been in the process of rebuilding an engine i've baught for spare.
About the same as you, some oil smoke at idle, clears when i ride, but if i let it idle for 2/3 min, starts smoking again.
I'm pretty sure O-ring were fine installed (checked 2-3 times) but maybe pinched them... i hope not!

Plates were lapped, brand new housings, ... everything else changed.

Thanks for your update.

Seb.

Sounds like we're in the same boat my friend haha! Identical issue. It's possible one got pinched or didn't seat all the way unfortunately. I've done a ton of research and asked every other engine builder I know and we can't come up with anything else at this point. Does yours show a misfire as well? I have a misfire code but the engine doesn't skip a beat whatsoever

No, not any misfire from the engine or DTC, only this small oil smoke at idle (not strait away, only after a few moment).

Seb.

Hello team,

Quick update by my side: No more Oil smoke at idle. Additional bonus, exhaust gaz smells lot less unburned gazoline.

So what was the point? This is only the Catalyser i was thinking ok, was dead. So when i was looking from the engine side to the cat, seems clean, but after i took off the lambda sensor, i've found almost clogged the 2nd half of the Cat.

I've change it for a new one, and now all is ok.

Hope this helps, maybe in the futur for other RX8 owner the have the same problem!

Seb.

Thanks for the update!! Still dealing with this problem on mine but I just continued to drive it for the summer and now it's away for the winter. I will check this out before I go any further!

OP had said that he replaced 3 of the 4 oil injectors. Curious if it could be the 4th.

When I was burning excessive oil, I had found that my plugs were getting coated. I suppose if it is only one rotor you should see a difference on the plugs if rotors are burning unevenly.

Otherwise taking out the Valves in the LIM may provide some insight if there is oil being sucked through the intake. Just something else to check before pulling the motor.