I have a 2004 AT RX8 and am trying to determine if the Metering Oil Pump is truly bad. My son and I removed the oil lines and started the car and I watched the ports as my son revved the engine and did not see any oil squirting or dripping from them. Is this normal or should I see oil coming from the ports? I would really like to figure out if it is bad before I pay to replace since it is so expensive. Any help would be greatly appreciated.

 

Suggest you put everything back together, note the oil level, drive aggressively a tank or two and check the oil level again. The oil injection relies of the pump but works best under vacuum so you really want the system to be complete. Also the injection rate goes with load, so revving in the driveway won't show much.

Premix 1 parts 2-stroke oil to 100 part gas while driving those tanks, in case the MOP is actually bad.

Other question: what symptoms do you have that lead to the bad MOP diagnosis?

 

That isn't a good test. The OMP is electronically controlled, and injects oil based on a table within the ECU. I don't think any is injected during cranking. You will need to get the engine under load to be able to see it, which won't happen outside of an engine dyno stand.

The ECU is pretty good at determining a bad OMP, and will flash the oil level light and throw one of a number of OMP error codes through OBD2.

 

Limp mode and P1688. Checked wiring already and switch had a resistance from 180 ohms to 280 ohms.

 

Have you gone through the shop manual diagnostics procedure for P1688?

 

Wish it could be driven aggressively! Limp mode makes that impossible.

 

Have not finished all checks yet.

 

While investigating...I noticed that the PCM does not appear to be grounded. After looking at drawings in the service manual it would appear that the PCM should have 2 mounting brackets which are somehow attached to the chasis ground. These 2 brackets are missing. The E2 connector which has the connections for the MOP also has blue RTV smeared on it and there is a large amount of electrical tape on the wiring before it exits the PCM mounting box. Looks fishy to me. If I were a betting man I would bet that one of these issues would be the likely candidate for my P1688 problem.


Any thoughts or information?

 

I wouldn't bet against you there. Hopefully the prior owner didn't deliberately try to disable the OMP...

 

I do not believe that the prior owner was exactly a genius. We bought the car last July and the owner claimed that it had bad apex seals. So far I am not convinced. With every thing that we do...Coils, wires, plugs...it appears to run better and better. We had thought that maybe the fella was right until we were told that it was in limp mode when we took it to the dealer for the PCM flash recall that our car never had. Once we cleared the codes it appeared that the car ran very well for about 8-10 seconds...then limp mode again. Fun fun fun.May try temporarily grounding PCM case. Any thoughts?

 

If he disabled the OMP under a belief that premixing would be better, then it's not the apex seals with the problem, but the side seals. I'm gonna guess that he was a prior RX-7 owner as well, and his attempt to transfer the knowledge ended poorly. It is a common problem with RX-7 owners that get an RX-8. Without the OMP, the side seals will fail relatively quickly.

If I was going to try to repair that car to working order, I'd probably pull the PCM and start testing and tracing every wire. Any wires cut or spliced I'd repair to get solid again. If I could find a harness from another car for relatively cheap, I'd swap in that.

 

Well I have an update and a question... After replacing the engine wiring harness and adjusting the OMP switch, it ran great for approximately 50 miles. It started running rough so I decided to run to the gas station and top off with fresh non premixed premium. On the way there I heard a sound like something was coming apart and getting chewed up...not good. the starter would not rotate the flywheel but definitely was trying to (dim lights while trying). Decided to remove the starter and investigate the starter and flywheel. everything looked good. drained the oil and removed pan...looks good, nothing out of place, no filings or debris in the oil or pan.

I did notice that a bolt which is located directly above the rear spark plugs had backed out a little over an inch. Does anyone know what this bolt's job is? I looked in the shop manual and was not able to find a good diagram. I wonder if this allowed something to move internally allowing something to get in the path of a rotating part and seized it up...( I cannot turn the crank with a ratchet and cheater either.)

Hope we don't need to spend a great deal at this point!

 

Directly above the spark plug pointing in the same driection as the spark plug. should be the knock sensor mounting point.

 

Thanks...while replacing the harness some moron (me) must have mounted the knock sensor at the wrong location. I appreciate the info.

Is there anything that would inhibit the crank from rotating while the transmission is in park and battery removed?

 

The Knock sensor goes on the rear rotor housing. And the bolt does not go through the housing.

Pull your spark plugs then try to turn it by hand with a wrench.