Hello, this is my first post so if I’m doing something wrong I’m sorry.

Last night I was doing some spirited driving and I got to 8k rpm in 3rd gear and when I shifted it started misfiring/bogging past 3k rpm. Now anytime I put more than 20% throttle or go past 3k ish rpm it misfires and prevents me. This is only under load as it will rev freely while I am in neutral. I don’t have a check engine light either.

Thank you in advance!

Any help or ideas on where to start would be amazing! I got the car two weeks ago (1992 R1) so it’s a bummer it’s already got something wrong with it but I’m eager to fix it.

 

Dirty fuel filter? Also, make sure your spark plug wires are ok.

 

Maybe a vac hose came off.

 

What ecu? Could be an engine protection being triggered.

 

I have the stock ecu

 

Nothing looks out of the ordinary and I was mistaken the rpm has nothing to do with it, it’s all throttle position. I can hold it at the edge in neutral right before it starts misfiring at 6k but once it starts eating **** it goes down to 3k.

 

Update
i was mistaken when it came to being an rpm related issue. It seems to be mostly throttle position, around more than 20% throttle it starts misfiring and buckling under load and while in neutral.

That seemed like a TPS problem so I put a multimeter to it and it was within spec.
With a warm engine
2nd plug closed 1.12VDC open 5.01VDC
4th plug closed .47VDC open 4.46VDC

I unplugged it and started it and it had a rougher idol, deceleration was very slow and wonky, and the misfiring and buckling was still there.

My very experienced friend still believes it to be bad. No disrespect to him, I don’t want to spend ~$400 on a new one when everything about it checks out and the problem is still there even when it’s disconnected.

Any help is appreciated, I just wanna be able to drive my car again

 

The only thing I could notice is that the second rotors trailing wire was loose to pull off but I took it off wiped it down and put it on with no change

I will replace the fuel filter but would that impact the motor with just one pull? This was a night and day difference not something I just noticed getting worse and worse

 

I once had an issue that felt like loss of boost at more than light throttle. Turned out to be a bad (high-resistance) plug wire. Because the engine is so smooth, it was not obvious that it was misfiring, but it was.
So, IMO, closely investigate the plug wires' conditions.

 

could I pull individual plugs to see if they’re is a difference while it’s running, or would that lead to bigger problems if I did that?

 

My car was doing the same. I ended up changing spark plugs and wires and it went away

 

Before you chase your tail any further, do a compression test. What you described is how a LOT of engines go. Make sure you have a solid baseline of a good engine before moving forward with troubleshooting.

I've seen people spend a ton of time and money looking at everything BUT the engine itself when that's the root of the problem.

Dale

 

im fairly confident it’s not that because it’s a fresh rebuilt engine less than 1000miles on the motor

 

Check the coils and leads imo. It's a simple test with a multimeter.

 

im swapping my TPS this weekend so I will check this then

 

Again, do a compression test. I had a friend with a fresh motor chase his tail for a full year on his car - turns out it was a stuck side seal and he was dropping compression on one rotor face, making the car run rough and weird. It was an error in assembly. Went back through the engine, got it freed up, all good.

I diagnosed that with a plain piston engine tester - the rotary tester is better/nicer, but you can do it with a cheap $30 piston tester. Just looking for a strong overall compression and even pulses on each rotor. If a rotor is low or has uneven pulses (1 or 2 faces low) you know you've got a problem.

I hope it isn't, but it's worth spending 15 minutes to do a test to rule that out before going down a deep rabbit hole of everything else. New motor doesn't mean it's without fault.

Dale

 

anyone looking at this after the fact it was a bad OMP and my car was in limp mode

 

Thanks for posting the update. How did you discover that the OMP was to blame?

 

had a buddy with a diagnostics reader check the codes and we had an OMP code and then I had gotten a PFC before having time to work on it and that showed 0.00 volts for the VMOP.

A friend and I tore the entire front half of the engine bay apart and the OMP connected falls right off... so it was just unplugged but looked like it was a bad OMP

 

I am having the same problem (OMP gone bad - got an error code) and the car goes into limp mode. I have bought a POWER FC (AP Engineering) and I am about to install it and fix the issue. I just want to ask if it is ok to just install the POWER FC and leave the OMP installed on the engine (also the feed lines and the oil injectors). Taking out the OMP is difficult and I read that the block off plates tend to leak after a while.

Also does anyone know if I can fix the limp mode issue by just plugging the oil injectors with bolts? It was mentioned as a solution to limp mode in an old thread but I think that the ECU will not be tricked by this. Any info on this?

 

You do realize there's a real good reason the OMP puts the car in limp mode? The engine will eat itself without extra oil.

Good used OMP's should be plentiful and they aren't hard to install. Get a new O-ring and you're good.

IMHO it's not worth fully blocking the system off and going full premix unless you have a full on race car. If you have a street car, leave the system be and add a little additional premix if you would like. The system works well.

Dale

 

The PFC has no limp mode. That will solve the limp mode issue, but obviously you’ll want to either fix the OMP or put some block off plates as a more permanent solution

 

Yes I am aware about the function of the OMP and I forgot to mention that I am already premixing. The problem is that a new OMP is extremely expensive (more than 1500 euros shipped) and the used ones usually fail in a short time. Also the block off plates tend to leak. That's why I want to keep the OMP on the car and install the PFC to bypass the limp mode by the stock ECU.

 

Ok, thanks for your reply. For the reasons that I explain in the previous post I prefer to premix and leave the OMP installed. Do you think that this will cause problems in the future (possible vacuum leaks for the OMP lines or injectors?)?.

 

OMP failures are actually uncommon, Mazda did a good job designing them. They should be plentiful and reasonably priced used.

Dale