I had a new engine installed 5 months ago. It was fine for the first few weeks but then one day when I started it, it accelerated very slow and it wouldnt rev over 3000 rpms. I turned it off and when I turned it on again it was fine. A week later the same thing happened. I took it then to Mazda and they said the throttle connection was "loose" and that they secured it. They charged me $90 for the useless service because it happened again the day after I took it home. The guy from Mazda said it was gonna be my throttle body that was bad, so I replaced it but it did not fix the problem. Now, I notice that when I start it from cold it usually does that same thing so I drive it for 15-20 mins and I turn it off and start it again and it usually works but sometimes as Im driving it just happens and the car slows down. I have also noticed when I drive it for a long time and turn it off, it happens when I try to drive it again. I have no idea what it can be but I have to fix it NOW!! Any help?

 

Likely Limp Mode....do some research...

possibly the MOP position switch needs tweaking?

 

what kind of tweaking can be done to the MOP position switch or how can i do it??

 

Please search..we have been over this numerous times and I don't want to get into it again in a new thread

 

what should i search under??

 

Adjusting mop...

 

^or OMP as many people call it so we don't confuse the OP.

 

Did you find a solution to your problem as I am facing a similar issue as well. I got the throttle body and accelerator peddle replaced upon advice from a mechanic but that hasn't changed the issue. it keeps happening again and again and I am fed up as well. Please advise.

Thanks

 

Any check engine lights?

 

It sounds like limp mode, which is most commonly caused by a problem in the OMP. If your mechanic familiar with rotaries? Because it sounds like he's guessing with your money. Accelerator pedal? really?

 

I’m feeling charitable today




The mounting holes in the MOP position switch shown above are slotted, which you can sort of see. Assuming your position switch isn’t bad, the ecu is looking for a certain reading on the position switch. By loosening the two screws, the slots allow you to rotate and set the initial position of the switch to provide the input signal that the ecu wants to see. My recommendation is to rotate full CW, then just a smidge CCW. You can keep adjusting it CCW in small increments until hopefully the ecu sees the signal it wants.

if you can’t get that to work then likely the switch is bad or the MOP has an internal problem. You can’t buy the switch separate from the MOP, so the only option is to replace the entire thing. The switch comes pre-adjusted from the factory and this adjustment procedure is not factory authorized. We’ve just learned that if the MOP is removed & reinstalled like on an engine rebuild etc. that things may not line up exactly like they were from the factory, or something might change with wear/time, and this is the way to possibly correct for it.

now there could be some other issue and reading the ecu codes is always best, but sometimes the switch being slightly out of position doesn’t provide a code. Well good luck.

 

I'm under the impression I have the lowest compression on the East Coast, but I can't find anywhere online saying "Low compression will kill your RPM if you let it get bad enough"

Fine by me, I'm gonna be replacing the engine with a 6 port anyway, but would like to drive it to the shop, not have it towed. Feels like I'm starting in 3rd in 1st, and stalls once it's warmed up and you try to move from a stop. Warmed up and moving is fine, and cold and stop is ok (still slow AF), but warmed up and stopped, once you try to move it dies.

 

That doesn't sound like low compression. Does it restart warm easily?
The 4000rpm ceiling sounds like limp mode for the OMP or clogged cat, dying sounds like vacuum leak / poor intake configuration / poor ignition.

Don't replace a 4port with a 6port, way too many headaches. Just buy another 6 port car.

 

Well I know for sure the ignition is solid (Almost brand new BHR with MSD wires and not 10 miles on the new plugs), she still dies without an air filter (right around the block, not trying to guillotine Stuart Little), and the cat gets hot but never glowing. Guess I'll check vacuum leak, OMP, or MAF

Edit: She absolutely hates warm starts. I just pop the hood, wait an hour after she died, and let her cool off before I start her

 

It was the cat! Gutted it and she runs like a dream. Kinda. Still low compression, but atleast it doesn't die while warm or choke itself