Limp mode, reoccurring... - causes?
 

Alright here is the story:

Picked my car up from the body shop and the engine sputtered and cut off under boost. Took it back and their Mazda tech was clueless so I came home and searched the forums. I read about limp mode so I reset the ECU, and it solved the problem. The car sat for a day. Then I started it up today and took it to get new tires (ran fine other than a little goofy on startup but this may be because it sat for almost 3 months at the body shop and moisture could have gotten in the gas tank). After they put on the new tires it was in limp mode again. I reset the ECU and it is still in limp mode.

I am going to start searching the forums and go check all the fluids. I really don't know where to start looking for the problem. Are there terminals that can be jumped to make sure that the engine fans work? I remember seeing something about faulty engine fans triggering limp mode and the engine fans were replaced with used ones due to the accident.

Any advice is greatly appreciated.

Thank you,
-Charlie

Might want to see if your ECU is throwing a code. There are a few things that will put you in limp mode.

check the codes, there are several that wont turn on the the check engine light

mike

Alright, it threw 1 code. - Code 73.

73 - Rear Secondary Injector open circuit

I am going to look over the wiring harness and see if it is all hooked up correctly.

-Charlie

I couldn't see anything wrong (couldn't see much of anything really). I am assuming that the injector is not bad because it did run fine once I reset the ECU the first time. My guess is that there is a bad connection or ground somewhere that is causing this code? Are there any known causes of this?

Thanks,
-Charlie

Alright. I am pretty sure that from a cold start the engine will not go into limp mode and will run fine. However, if I start it after it has been warmed up it jumps to limp mode.

-Charlie

Alright a new update. I've been doing some reading and beginning to suspect the fuse box at the front of the car that houses the fuel pump relay. Since this part was damaged and they started to replace it but opted to leave it in since it would have taken too long to disconnect all the wires I think it might have a short. I used a voltage meter and the fuel pump relay seems to be just like one of the other relays I tested.

So I tested the holes the fuel pump relay plugs into. It is NOT the same as the A/C plug (the one next to it). On the fuel pump relay spot every hole is a closed connection with the other. I am pretty sure that means there is a short, unless this is different than the A/C relay plug which doesn't have a closed connection on every hole.

Anyway, I'm going to start taking the fuse box apart and see what I can see.

-Charlie

I'm looking at the wiring diagram (Z-30 in the 1994 FSM), and the rear secondary injector wiring has two wires: one goes to the EGI Main Relay, and the other goes to the PCM. The wire that goes to the EGI relay is tied, in parallel, to all four of the injectors. If you are only setting the code for the rear secondary, then there is probably an open circuit between the injector / pcm, or injector / EGI relay wiring (whereever that connection is). I doubt you have a bad relay or fuse, or else all of the injectors would be messed up.

That's what I thought originally but then I found this thread - https://www.rx7club.com/forum/showth...injector+relay - It says that you can drive the car without even having the fuel pump relay because it only controllers the heavier load (when the secondaries come on). It says if it isn't in or isn't working the car will fall on its face when the secondaries come on. I just figure its worth a try.

-Charlie

Just to clarify I am talking about the fuel pump relay in the nose of the car. In the shop manual they refer to it as Fuel Pump relay (SPEED).

I could really use a wiring diagram for the fuse box that is located in the nose. I know for sure that the tech at Mazda had the wires from the fuel pump relay unplugged when he was changing the box and then decided it would take to long so he put them back in. I am thinking maybe he put them in the wrong spots, or there is a short somewhere.

-Charlie

hey this happened to me as well, here is was a thread about this: https://www.rx7club.com/forum/showth...threadid=96187

for me it was error 51, the fuel pump relay was busted. after the switch to a new one (~$100 from Mazda) the reoccurring limp mode stopped returning.

perhaps this shall help.
Edgardo

Hm. Well I guess if the problem was with my relay or the wires to it I would be getting a code 51 instead of 73. I guess I'll pull the intake and take a look at the injectors.

Thanks,
-Charlie