-OK, 1st post. I bought a 90 vert with a few issues. The omp/mop is bad, guy said he opened the flow to max so as not to damage the eng., is that ok?
-I also understand that the bad omp causes the limp mode that I'm getting, but will it cause the backfire i get after some hard throttle?
-The car has 103000 mi with a non-original engine; how can I tell what year/type engine has been installed? Location of identifier/decoding link ect.
-Thanks in advance, Tim.

 

If the OMP is truly bad you need to immediately (not on the next tank) add some two-stroke oil to the gas. I think that 1 oz per gallon is a standard rate. This will protect your engine while you sort this out. This is also not enough to cause problems if the OMP is functional.

I do not think that the S5 OMP has a 'flow' that can be opened. If it is not working, how can it flow more? A quick check of the FSM did not show any adjustment, but that is as far as I know.

BTW, a bad OMP on the S5 has the capability of shorting out the ECU, so do not ignore this for long.

Good Luck, welcome to the world of verts!

 

I would believe the omp is functional because of the smoke puffing from the tailpipe, but Ill have to add oil to be safe. Also, I'm new to the terminology, whats s5 signify?

 

s5 is a series 5, the 89-92 model of rx-7

 

Well, an Rtek 2.0 will allow you to run the s4 (86-88) mechanical OMP. It may be cheaper to get a new S5 one though, I luckily haven't had to price it out yet.
Definitely get some two stroke oil in there.

You can also dump the error codes off the ECU and see what all is being detected as wrong

 

ok then...

1. if the S5 OMP goes out it usually takes the ECU with it. my advice premix and get the Rtek chip and have them put it in. it only cost 115. unless you want to buy a new OMP and a new ECU and replace everything there.

2. yes, that does cause the limp mode.

3. im not to sure on that one.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/

here. read this thread about the S5 OMP.

 

Wow. Great discusion on that thread. It just makes me want to rip out my ECU and see what needs fixed. Unfortunately since MY 90 vert is also coding a bad MOP I may end up doing something like that. However, based on your comment about the RTEK chip, is it possible that I could use that chip and then just premix? - no limp mode.

 

im going to install it as soon as i get the money for it. ill let you know how it works.

 

The OMP motor is a plunger type steping motor, all the way in it allow a very small amount of oil, a standard idle amount, as the rpms and throttle increase, the stepped motor spins and slowly protrudes a shaft agianst a spring and allows more and more oil gradually.....

i have a "broken" omp sitting in a box, the motors shaft was bent, so i twisted it around until it was about 40 percent open so at idle i was injecting to much oil into the engine, and above 40 it was too little, this was on a car that was on it's last leg and was just trying to revent Limp MODE, which went away although the
OMP is technically broken, go figure... now a save it to diagnose other cars :P

 

Cars sold in the U.S. between 89-92. You would do well to read the FAQ.