Leaking OIL injectors
 

Hi all!

I've searched for this info, but couldn't find anything.

After taking apart my engine we've found out that all 4 oil injectors are faulty (you can blow through the vacuum hole)

The engine was torn apart because of low compression (~80psi each chamber both rotors).

When we torn apart the engine, inside it looked like all the wear was due to the insufficient oiling.

Two questions:
1) Do i get it right, if oil injectors are faulty, like described above, the engine will not get sufficient oiling, because some oil will be sucked into vacuum tubing?
2) What could be the reason of all 4 (!) injectors became faulty on a nicely maintained car with 52000km odo and oil changed every 5k km? No racing and only genuine oil and parts?

Thanks in advance.

IF you can "suck" air from the vacuum connection it is bad. Air should be able to flow from the vacuum line to the side that screws into the engine.

Thanks, but I know the procedure and all 4 injectors are bad. That was not the question.

Sorry the way you described it, it seems like you were blowing air the wrong way for the test.

Not sure why it happened, I'll leave that to someone else...

Thanks for your response anyway ;)

So. R u actually blowing air thru or sucking air thru?

Actually both :) air comes freely in both directions. They're faulty for sure.

No ideas?

I think no one will answer because
1) first post you described (IMO) the wrong way to test. But you later stated you can blow air both ways, which does mean they are bad.

2) no one will really know as to "why" it happened. It could be anything really. Maybe it sat up for a long time and they gummed up. Maybe you do a lot of very short trips or do not drive the car a lot and try gummed up... Possibilities are endless really.

Same problem
 

Just did a rebuild on mine after the engine blew. Engine wouldn't idle well after the rebuild. Often a vacuum leak problem causing this.

Tested the injectors on the engine using a vacuum pump, and all 4 are bad. Pulled them out and they test bad off the engine, too (I know this may be obvious to some of you).

No idea why all 4 would go bad at once. Engine rebuild shop said my bearings were trashed and wondered whether I had ever changed the oil (A: yes, religiously every 3k, plus premix at the track).

Mine's a 2004, 60k miles at rebuild.

Yeah two out of four were bad for me but that won't affect the bearings, what kind of oil did you use?

Can a bad oil injector also cause excessive blue exhaust smoke on some cold startup?? Or ANY startup for that matter ?

It wasn’t less than the 9.65 right?

__________________________

https://cimg5.ibsrv.net/gimg/www.rx8...26a393e5c.jpeg


They also don’t affect idle the way you’re thinking. That connection is piped to the intake accordion just before the throttle body opening. While they do bleed into the engine, this is calculated as part of the total idle flow by the MAF (assuming you don’t have hose leaks). No different than the air bleed nozzles for the primary intake ports. It’s all going to the same place and in total, just taking various paths.
.

How does that make any sense relative to your prior comment about getting 10 psig vacuum?

Try an engine compression test next. A bad idle isn’t necessarily a vacuum leak.
.

Well, the test states to hook it up as shown and if you can’t achieve the vacuum pressure shown then to replace it. It seems rather straightforward.

if you have a vacuum leak it’s coming from outside the intake system bypassing the MAF sensor. If the oil injector piping is all hooked up properly and not leaking then it can’t be that per my earlier explanation.

Not much anyone can do to help you track down a vacuum leak. You can try spraying carb fluid around while the engine is idling to detect an approximate location when the engine revs up if it gets sucked in, but otherwise it’s just methodical testing that has to be performed in person. It could literally be anything.

Well let me dig up an oil injector and check it, because I’ve never had any old enough to bother with. I have a bunch of low mileage ones I know are all good, but I’m telling you that has nothing to do with your idle issue. It all comes past the MAF, whether it goes through the throttle body or not doesn’t matter

That’s exactly what I’ve told you and clearly you don’t understand.

The air that goes by the MAF the ecu sees and adjusts for. It’s the air leaking into the intake that’s not going by the MAF is what causes the high trim number you have The oil injectors are intentionally designed to leak air into the engine. This is part of the idle air system. The vacuum test we were discussing previously is to test for air flowing in the opposite direction; out of the engine, not into it.

+23 is pretty big. Often the VFAD nipple and line are overlooked...

The key point earlier is that even if they do leak, they get their air post-MAF, so it's metered air and not a vacuum leak to the outside. Your root cause is elsewhere

It pulls air into the chamber to avoid sucking oil in uncontrolled. The purpose of the metering pump is to pump oil in in a very controlled way. If vacuum pulls oil in it will not be controlled because vacuum varies greatly depending on the engine operating condition. Which is also actually the opposite of when oil needs to be injected. Vacuum is very high on low engine load and very low on high engine load, but oil injection is not needed as much during low load as it is during very high engine load.

You also still are not comprehending that when you perform the vacuum test you’re trying to pull air in the opposite direction that the engine does when it sucks air through the oil injector nozzle. When the engine is running it’s pulling a vacuum on the big threaded end of the nozzle. For the test the vacuum is being pulled from the opposite small nipple end. There’s a check valve in there for flow in that direction. That’s what you’re testing. Which is why this problem you’re having is not influenced by the oil injectors. This test is to make sure they operate properly with regard to the oil metering pump function.

As stated in the last point below and per the diagram:

https://cimg0.ibsrv.net/gimg/www.rx8...6c72c2c8f.jpeg
.

No, you are completely confused and not thinking it through properly.

So that prior test diagram is actually not complete. It’s probably out of the common online service manual that was pre-RX8 production and not entirely accurate. You need to go buy a real Mazda RX8 service manual for the correct model year. This is out of the 2005 manual:


https://cimg2.ibsrv.net/gimg/www.rx8...b858ca599.jpeg

So this is maybe where you’re confused. The air line to the top of the oil injectors is connected to the intake accordion tube *before* the throttle body. Vacuum doesn’t occur until *after* the throttle body. Which the big threaded end of the oil injector is in the intake side of the rotor housing and it is under vacuum during the intake phase of the turning rotor. The small nipple end of the oil injector only sees atmospheric air pressure because the air supply hose is before the throttle body.


https://cimg1.ibsrv.net/gimg/www.rx8...0de4c64fb.jpeg

Sorry, no. Those lines can’t be broken or it will allow air into the intake after the MAF.

sorry, initially misread your reply.

They have to be sealed and not leaking between the end points. Any air getting into the intake after the MAF is going to result in a lean AFR condition that the ecu will try to correct by adding fuel trim.
.