I have any 86 rx7. I put an 88 turbo rotary in it and now it cuts out, and back fires at 4000rpm when I release the accelerator. The secondary injector in the rear clicks spontaniously the other one works fine and the primarys work fine. I changde all 4 injectors and no difference. The airflow meter and boost sensor came with the engine, and the wiring harness to the mafm and boost sensor was cut, I got a harness at pick n pull off a non turbo not sure if the wire connections are right , PLEASE HELP BEEN TRING EVERTHING FOR 3 MONTHS!!!!

 

Thread moved to 2nd Generation Specific. For future reference, "Help" threads such as this do not belong in Build Threads. Please post in the correct section.

Have you read the FAQ? Here is a link to it, please bookmark it for future reference as you will find it incredibly useful:
https://www.rx7club.com/2nd-generati...faq-fc-494667/
From there, download the S4 (1986-1988) Factory Service Manual (including the Wiring Diagrams) in the following link:
Foxed.ca - Mazda RX-7 Manuals

Thankfully, Mazda was very thoughtful in making wire colors consistent between N/A and TII cars. Injectors are rather simple, only having a signal (straight line to ECU, one per injector) and power (ignition-switched, only active when key is on). You can test this with a multimeter set to Ohms. This is called a Continuity Test.

Unplug the injector in question, put one probe touching one of the terminals in the connector and the other on the battery positive terminal. Then turn the key to ON. I forget which terminal it is (check the wiring diagram), but the multimeter should read ~0.07 ohms if the wiring is good. If there is a poor connection, it will read higher. I personally consider 0.10 ohms or more to be in need of repair.

If the meter doesn't respond (stays at 1_ _ _, meaning infinite resistance) when you turn the key, this means there is nothing linking the two probes. Just to be on the safe side, repeat the test on the injector's other terminal as well. The actual polarity doesn't matter on an injector, it just needs power and ground (signal from ECU) to inject fuel. The ECU pulses the ground to vary how much fuel is injected.

I'm not sure if there is an appreciable difference between a N/A and TII Airflow Meter (try searching Aaron Cake's posts for info on it), but the MAP Sensors are definitely different. You need to use a TII MAP Sensor on this, identified by N318 on its label. The S5T2 MAP sensor (labeled N370) would also work. Downloading the Parts Catalogs would help identify what you are working with since Mazda was quite generous with labeling parts distinctly. S4 N/A-specific parts begin with N326 while TII ones are N318 (shared with J-spec) or N331, N332 or N333. If you look at the Parts Catalog at the same part for both NA & TII, everything but the prefix is the same. For example, the Alternator for the N/A is N326-18-400 while the TII version is N318-18-400.

Differences between the N/A & TII Emission Harnesses are pretty well documented. The N/A Harness has no provision for the Turbocharger Wastegate solenoid, while the TII has the Alternator connector in the Engine Harness instead. The Engine Harness is what the underhood fuse panel is a part of, while the Emission Harness contains wiring for the injectors, MAP Sensor and so on.

I would HIGHLY recommend reading Aaron Cake's Project Tina build to better familiarize yourself with this project. Link here: My RX-7: Project Tina If you are still stuck after this and going through the Wiring Diagrams, reply and I'll see what we can do to get it straightened out.

thanks,
AWC

 

which ECU are you using?

 

Thanks for the advice, ill check it out.

 

The ecu came with the engine and the label is peeled off but I think its n318.

 

No such thing as a N318 ecu.

 

Im not sure which ecu it has... came with the enginen when I bought it. Its has a few dents on it maybe it got damaged? Im using a non turbo airflow meter on it currently because when I put the turbo airflow meter in, the car barely runs. Is the wiring for a non turbo afm diffrent?

 

WOW. this sounds like a hot mess. You have photos of the engine bay or something to start with.. its not much. But are you sure you are using all S4 Electronics and parts?

 

Im using all s4 electronics except for the air flow meter. Im thinking since im using the wire harness to the afm from a non turbo maybe the wires are in the wrong spot for the turbo afm? The place I got the engine from cut the harness going to the boost sensor and airflow meter so im not sure if they are wired correct for the engine.

 

The airflow meter has 7 wires going to it so I hooked the wires up according to a non turbo harness to a non turbo afm. Do you know the wire pattern for the turbo airflow meter?

 

its frustrating been trying alomost everything to fix it and changing everything. Had the car for 10 years so its a good hobby but would like it to run good. Im not sure why it barely runs with the correct afm does anybody know the wire pattern for the turbo afm?

 

Dude, you cant use a s5 air flow meter on a s4 ecu. Put the same afm as the ecu and hopefully the rest of the accessories. Dont interchange s4/s5 electronics. Its almost like 2 totally different cars. Ive been down this road.

 

Just took that pic of engine bay if you look were the wires go to the afm they are all spliced, im not sure if they are right

 

But when I put the correct afm for the computer the car will barely run.

 

I checked the resistence to that rear secondary injector that clicks spontaniously and the resistence from the ecu is pretty high. How do you fix it? Does that mean I need a new ecu or could something on the car cause that injector to not work properly?

 

Switch the two secondary injectors and see if the behavior moves with injector (bad injector) or stays on the same side (wiring or ECU)

 

Then your hacked harness is garbage. Put the s4 afm back on and start looking for a new harness before your ruin a ecu, if its not already.

And if your injector plug-ins are backwards it will barely run. Make sure injectors are properly hooked up.

 

I tried that last weekend and it stays on that same injector, then I bought new injectors but it made no diffrence.

 

Do you think it would damage the ecu with the wrong afm plugged in?Is there anyway to test it to see if its still good? Ill probably have to get a new harness to fix the problem

 

The car originaly was a non turbo I didnt change out the wiring in the dash. Do you think I should do that too?

 

Yes, if you have them spliced wrong. Sending too much voltage to the ecu will fry it fast.

And the body harness wont matter. As long as the chassis harness grounds are all in and good. Just get a new engine harness to make things easy.

 

Thanks ill look into a new harness do you think that will make the one injector start working good or do you think its something wrong with the ecu?

 

You need a turbo harness and ECU. NA harness and NA ECU are not the same.

Don't hack the wiring harness. And the engine bay looks good besides the harness. But i still cant see what AFM you are using. Make sure its 86-88 and not a 89. does the AFM have a flapper or a ball type round inlet? I didnt check to even see if they have the same pin or plug. thats why i am asking I am not in the garage

 

It has a flapper im pretty sure its the right one I got it a kregan the other day just cant put it on because it will run like crap

 

You can use a s4 na harness with a s4 turbo ecu. I currently use a na harness on my t2. So you can look for either. Just make sure everything stays in the same series, 86-88 and you should be good.