I have a sick OMP in my 89 GTU. Because of $$ and the high mileage I already have on the car, I plan to run premix, but the ecu puts the car into limp mode.
Anyone know whether the ecu can be fooled into thinking all is well with the electronic omp? I thought the omp feedback to the ecu was a resistance. Could I simply brigde the omp connections at the ecu with a certain ohm resistor?

Thanks.
Desperate

 

There is a thread on this. I beleive they are still working on a solution for it. The thing is that the ECU needs varying figures with RPM so you can't just leave it at one setting. You could probably set something up if you know electronics but I personally am a beginer with this stuff. :-/

 

I think that the varying signal is used to adjust the amount of oil to be fed by the omp. There might be some middle value that I could just use to avoid pokey mode.

Or, do you think that the varying OMP signal to the ECU affects other engine settings (advance, fuel injected, etc)?

I have a slow computer. Do you recall where the thread discussing this issue was?

Thanks

 

The ECU NEEDs to see different values or it will go into limp mode.


Let me look for the thread.

 

https://www.rx7club.com/forum/showth...&highlight=MOP

That should be it.

 

really appreciate the help. thanks much.

 

Not a problem. Happy to be of help.


Santiago

 

won't work. just take a look at the OMP. it has 9 wires. too hard to fake. the best solution people have for premix is to tie up the OMP somewhere off the engine with it sill pluged in. of course this would require it to be working in the first place.

 

Somebody must have a used OMP that they can throw at this guy. I've gotten just about everything I need for my car off of this forum.

 

i bought mine from someone on the forum for about 50 bucks...dont pay more than that shipped, unless your desperate. remember this particular part is something like 1k at the dealer heheh but yeah you need a working one no if, ands, or buts...

Fred

 

I've said it before, and I'll say it again: anyone with a little electronics knowledge could build a circuit based on a microcontroller easily fool the ECU. I have this on my long list of things to do, but I doubt it will ever be completed since I have not motivation. I don't have an S5, and prefer the stock MOP to premix.

My "solution" would literally cost the buy $50, and would be plug and play in 5 minutes.

 

Visited the local dealer who wanted $1500 for a new omp (without lines, labor other fittings). A local mechanic that I trust spoke of 5 hrs or so of labor for him to replace the unit, but also had concerns with aged, brittle oiling lines, and how tricky it might be to not crack lines during installation (without the engine pulled) and not knowing how reliable the replacement unit would be. I'm not very mechanically inclined (skills limited to minor tune-up and brakes) like so many of the posters at this site. Plus, because my rx7 has 216k miles (original motor!), minor but noticeable dents/dings in both doors, front fenders and r qtr panel, I can't justify a major repair bill. I love the way the car drives and how tossable it is, and prefer to keep it (wife won't let me have another 2-seater, though in the future I might be able to slip the rx8 past her) and aside from the poke mode it starts and runs too well to put out to pasture. So that's why I'm hoping for the cheap electronic trick fix to get around the poke mode.

What have been your experience in replacing one of these units?

The thread mentioned a few notes back had some good info and some simple things for me try, despite some concern about a need for varying voltage feedback. I can set up a 'voltage divider' to feed 3, 4 or whatever voltage to the ecu. My question about this..... what total resistance would be recommended (to avoid 'shorting' with real low ohm resistance or at the other extreme have too high a resistance that will affect the reading by the ecu. I'm trying to avoid mismatching output and input impedances.

 

Oops - I'll try again.

 

You are trying to simulate a bi-directional stepper motor with an attached variable resistor position sensor.

They don't often fail. Usually it's a bad connector or a short in the harness.

My "ECU failure" last spring turned out to be a bad connector pin in the tranny neutral switch plug.

Good luck.