Once in a while during a search I'll see where someone says that something not working will put the car in "Limp Home" mode.
What exactly is that, what does the car behave like, and what are the common causes for it?
I'm still trying to chase down my "6K=no power, 7K=rev limit" problem.

S5 NA. No error code. New plugs, new fuel filter. I have yet to test electrical, injectors or pump. Ran w/O2 sensor unplugged with no difference. Thought that might put it into Limp Home mode, and I wanted to see if what I'm experiencing is that or not.

Thanks all.

 

From what i understand limp mode is when the ECU runs a map that will basically let the engine run at type of circumstance. This is due to a sensor of somesort not working so the ECU doesnt know whats going on. They call it limp mode cause its basicaly just there to get the car home or to shop. So thats why it will run crappy cause its a base map that is just to get the car someplace. Idk if thats true for the rx7s but thats what i've heard from other cars. Correct me if im wrong please.

And if you unpluged the o2 sensor and theres no change chances are that is bad. Although if you didnt get a code then maybe not idk. Someone else needs to chime in.

 

Limp MODE
1. can only be activated by the failure of the OMP(oil metering pump), or it's cirucits within the ecu, usually when the OMP fries, it takes out the omp control within the ecu. NO other sensors will activate LIMP MODE.

2. after you start the vehical it takes about 4 seconds for the check engine light to come on, and limp mode to be active.

3. you cannot exceed 3500 rpm, or fuel will be cut to the REAR rotor.

4. You cannot exceed ~30 percent throttle, or fuel will be cut to the FRONT rotor.
you can down shift(to get above 3500 rpm) and floor the pedal and get no fuel at ALL.

you can turn the car off and back on, and have a 4 second window to redline the motor at will. but it's not advised. i've blown a motor like this.

welcome.

 

I have had a bad engine ground trigger limp mode.

Your tach will be dead as the computer also stops firing the trailing coils.

 

well, you need a ground for the OMP to work... and no the tach does NOT die when in limp mode, you had some other issues, it cuts FUEL not spark.

 

It cuts the trailing coils only. And yes it is very likely that the OMP was the source of that particular issue indirectly.

If your tach works your car is not in limp mode. It fixes the ignition timing (disables the advance) and only fires the leading coils.

But, the OMP is not the only thing that will put the car in limp mode. Certain failures and code associated with the AFM will also put it into limp mode.

 

Thanks for that great explanation.
Obviously, I am not experiencing Limp mode. Unfortunately, now that I know there is only one reason for the car to go into limp mode, it didn't narrow down my list of possible causes much! LOL

Hooked the O2 sensor back up and cleared the two codes that I got as a result (12 & 18) and now I get no codes again. If some more knowledgeable folks could tell me a few more things that they think is NOT my problem, it would really help me to narrow down my search (-and I would be very grateful...). I get only a few minutes a day to do anything with the car, so it gets pretty frustrating chasing my tail.

 

I believe that the 12 and 18 codes are for the TPS, not the O2 sensor.

 

we seriously need a report false/incorrect information button.

 

Yea, the tach works just fine under limp mode. I had a s5 t2 with a bad OMP, every ten minutes it would go into limp mode.

 

I think you're misunderstanding.
I pulled the O2 sensor (disconnected it) thinking it would force the car into Limp Mode, not realizing that it would not. I did this to see if there was a difference in the way the car was behaving with my current problem, and Limp Mode; -IE, I wanted to see if what I was experiencing was Limp Home Mode because I could not find any description of it.
Prior to yanking the O2 sensor, the engine threw no code what so ever. While the O2 was yanked, the codes thrown were #12 & # 18. That was the first time I had witnessed any codes. I removed the battery ground, reconnected the O2 sensor, reconnected the battery, hit the brake pedal, and it threw no code, just as before I disconnected the O2 sensor.
Though code #s 12 & 18 may indicate another sensor, (IDK, I haven't looked at the list recently) it clearly threw those codes as a result, directly or indirectly, of pulling the O2 sensor.

At any rate, If I could get a few suggestions as to what my problem is most probably NOT, I can check them off the list. This is a new approach for me, after trying to ask (and search, extensively...) for what my problem likely is.

 

Tach works in limp mode.

Your problem does not sound like limp mode.


Wanna experience limp mode? Unplug the OMP. INstant limp mode.

 

Thanks for the insight. I ******* get it already.
I am trying to find help with THIS:I'll just start another thread...

 

No problem, asshat. You asked for suggestions as to what your problem was NOT so you could 'check things off your list'. Rather than a description of the limp mode (which you already had) and since you were trying unsuccessfully to force limp mode, I made a suggestion on how you could experience it. So you could check it off your list.



Have fun with your problem. Try to get it solved before you alienate everyone who could possibly help.

 

jack and sterling you guys knock it off, if you dont know sterling go to the 1st gen section, he's an old timer just catching up with the rest of the EFI world.

Sterling, pull your cats and see if you get some power, or can rev higher, it sounds like they may be clogged. You dont have to remove them, just the bolts on the first flange were the engine meets the tranny. and just pry it open so exhaust can excape.

 

I don't know if you are ever gonna read this but I really thank you for this description!!!
I have been trying to troubleshoot my car that behaves exactly like that!!!
Thank you so much!!

 

Check CEL code.

 

I have checked them with the mazda self diagnosis checker. Here are the results. I am copying from my original thread. Here is the link of that thread with the whole story (https://www.rx7club.com/2nd-generati...nside-1142527/)

8, 11, 18, 26, 27, 33, 34, 37, 38

8 is AFM. I replaced the old one few months ago as I said previously with a used one from ebay. I measure the resistance according to the FSM and the values are within range.
11 is air intake temp sensor. I installed a brand new one few months ago. How can this be broken?
18 is TPS. Also I installed a new one few months ago. Can it be damaged in such a short time?
26, 27 and 37 are the OMP errors. I think that this might causing my problems. Maybe what I am trying to describe for so long in here is a limp mode. I also read in another thread that the OMP could also fry the ECU.
33 are the rats nest solenoids. I tried to check them and realized that my car although that is an S5 has 4 rats nest solenoids! I read in the FSM that S5s have 3 and S4s have 4. I am really confused about it...12 years ago I installed a new motor core. Probably the guy who installed it changed my rats nest...I really don't know what is going on.
34 is the BAC. I have removed it.
38 is the AWS (removed) and the ASV. I have ordered a brand new ASV from the mazda dealer.

 

thanks for your reply! I thought that this thread is dead

 

A couple years ago the OMP on our '89 TII went out about 45 minutes from home, but got home albeit in limp mode.
Replaced the OMP and ecu was fine.

 

Yesterday I checked for leaks and there are no any visible leaks. I also checked the harnesses of the MOP and they look fine. I also spayed some electrical contact spray but the oil lines seem to be empty from oil.
I have bought an APEXi POWER FC and I was thinking to delete the MOP and start premixing. A new MOP is really expensive here in Greece. Do you think that I can rebuild the MOP and make it work again?