Hey guys I have been getting the error code 27 lately and my car goes into limp mode usually while cold. I have read many threads on the mop failures and options to fix it none of which are super specific. I have figured out pretty much I don't want to replace it based on its price so I want to bypass it and run premix. My question is what specifically do I need to buy to bypass the mop and stop going into limp mode. My car is stock.

 

You can't practically by-pass it on the stock ECU. A standalone or a used OMP is more practical IMO. If you search under my username I did a how-to on changing out the OMP. IIRC, there are others as well.
You also might want to take a read through this:https://www.rx7club.com/3rd-generati...g-omp-1073113/

 

Thanks for the reply...I figured I was going to have to do something with the ecu and I have been contemplating going to the apexi power fc if that will work but i didnt know if there was a cheaper option...

 

The mop itself is pretty inexpensive to change out for a used one. I sold mine a while back for 50 bucks.

 

With a PFC you can delete the OMP/MOP with a block-off plate and pre-mix. It will take it out of limp mode with no CEL. A sensor check on the PFC Commander will just show the MOP shaded.
But IMHO, you might want to swap it out. Granted it's a small PITA to do with the engine in the car, but that would be your cheapest option.

 

Ok I just bought a good condition mop off an engine with less than 50000 miles for $50 so i may just stick to replacing it....Where is the MOP located on the engine though I cannot seem to find a diagram for it...Do i get to it from the top of the engine or underneath the car?

 

Right front of engine, just to the right (passenger side) of the main pulley you should be able to see it.
I did mine from underneath, but IIRC others have had success from above. Your call. Here's that thread I mentioned earlier if it helps:
https://www.rx7club.com/3rd-generati...my-how-675341/
And as mentioned in that thread, I'd use a new 'O' Ring and crush-washers.

 

Awesome man thanks youve been a huge help! Looking at the complexity if its less than a feww hundred bux in labor I may just pay to have it installed just cuz im saving so much on the part...well see

 

whileon you are waiting for the install, you can get out of limp mode and use Premix by "tricking" the ECU.

I'm doing this now; you unplug your dead OMP, plug in your replacement (plug is on top behind the alternator. Then you can just hang the new OMP anywhere in the engine bay away from the belts, I hung mine on the strut brace just behind the power steering pump.

Not a Fix, but it lets you get out of limp mode until you make the install permanent.

 

good info....mine gets out of limp mode when i turn the car off and back on..Its pretty sparatic today i didnt get the code or go into limp mode all day so it happens randomly

 

PS Pritchard beautiful car what size rims are those and are you lowered?

 

18in ADRs, not lowered -- just 175,000 miles tired.
thanks

 

Nice Man I just put on the cwest light kit myself...did you have to roll your fenders to fit the 18 inch wheels or what width are they?

 

no, 18's usually fit with no changes.

 

So just as an update I received the OMP that I ordered today and lo and behold it was an FC OMP with the 2 harness connectors instead of the 1 connector on the FD. Sooo I set out to do something drastic I cut the wire harness connectors off the fd connector currently on my car and soldered it onto the wires from the fc harness...all wires were the same color on the fc and the fd harness so it was easy. just cut strip solder tape. Anyhow I plugged it in to the car harness and tied it up in the engine bay as ppritchard stated to test and boom it put my car out of limp mode!

so let the record show that an fc omp will work on an fd with the proper connector. when I go to mount it up to the block there will be further modification to the oil lines from what I can tell it wont be a big deal though. I will report back.

 

Good to know. I'm sure Fritz has some FD pumps though, if you want to have the fitment right.

don't forget the premix while you're in between.

 

******* hell of a day installing this bitch....broke my oil fill tube trying to get to the vaccuum tank bolt behind it after the tank was loose i realize i cant remove it without taking half of the engine apart so it was pointless to even loosen it. Cant get me new omp harness connector run to the connector on the engine harness.....fuuuuuuuuccccckkkkkkk idk why i even attempted this ****

 

Sorry to hear that. If I'm understanding correctly, your problem is the same as I addressed in that how-to.......

 

Yeah its the same problem I flexed on my oil filler neck but it broke right at the base where it mounts and Im hoping that no small plastic pieces fell into my engine but now im struggling with fishing the new wire harness connector from the new omp up behind the water pump and into position to be connected to the engine harness...

 

The stock setup has the wires run up under the bottom pulley and up to the alternator.

You "can" go the other way, over the air pump and straight across the top to the plug.

I'm going that way because a thrown belt cut my wires last time and I don't want to have that able to happen again. I think it's a little shorter and might give you some play.

 

DAMN I wish I knew that before I broke my oil neck haha its all good I gorilla glued it back together and it looked like a very clean break no chunks missing or anything which was awesome the gorilla glue held up really well too. I ended up having to remove the alternator all together and the alternator bracket which let me remove the vacuum chamber...

Hiccups so far:
-rounded one of the stuck power steering bolts that I then had to grind off and drill out huge pita
-broke oil filler neck trying to flex it to get to the vaccum chamber bolt (that wont be going back into the engine) might zip tie thru the bolt hole instead that way I can get to it easier next time if need be.
-pulling the nut that held the alternator bracket ended up pulling the stud all the way out due to heavy rust. then it didn't want to go back in all the way. managed to get it done with some pb blaster.
- tore the alternator belt trying to get it off the car

Is there any secret to pulling the alternator belt off??? I have a feeling that mine was a hair too short because even with the alternator fully off the bracket it was tight and I had to pry it off with a screw driver which tore the belt....Any suggestions welcome...

 

Stock pulleys? The air pump has it's own tension adjustment.

 

Now I'm not sure if it's stock pulleys...I went to get a replacement at advance auto and they were only listing a serpentine belt for the alternator but it's very clearly a ribbed v belt soooo idk I'm gonna have to bring in the belt to match it

 

A 'V' belt on an FD?

 

My mistake advanced auto computer was listing:

1993 rx7 belts:
- V-belt: Power steering and air conditioner
- serpentine belt: alternator

this confused me so I left. After thinking about it neither is a v belt...