just got a 1991 FC


I was aware of issues before i bought it....

so here it is,

MAF plugged in, tries to start and dies.
MAF unplugged, starts and idles HIGH after warming up a little(not complete), the idle the fluctuates.
(TPS has supposedly been replaced)
it has been sitting for about 2 years, run briefly "every once in a while"

There is a way to check codes on these, anyone have a link?(found service manual)

View My Video

 

RX7 FD and Series 5 Error Codes CODES

Foxed.ca Manuals.

 

Something is odd. With the AFM unplugged, it should start then die. Not absolutely not continue running.

If it has been sitting, first step is a basic tuneup. And then an overhaul of the fuel system including having the injectors professionally cleaned.

 

8, 10, 33
AFM Disconnected.
Air Flow Meter (AFM)
Intake Air Thermosensor (AFM)
Solenoid Valve (Port Air Bypass)

 

okay, so tested out the AFM, it's checking out fine via Resistance checks per shop manual. still does not run with AFM connected starts and dies, however runs poorly with it disconnected. i thought it was supposed to be the other way around!

 

Found a cap on the back of the plenum(circled in blue) capped off. then found a disconnected hose and a capped T on the same line, who knows where these go? tried looking at the vacuum diagram, didnt help me much. also what is the white plastic piece(Rx7 Manual Thermal Wax Valve) the lines are coming from?

 

The hose end where your finger is should not be open but capped if it's not going to be hooked up properly. The FSM has a diagram of how these particular hoses run (found in the emission section). You could also use the advanced search feature and find numerous pictures/diagrams of the hoses in question. Also, there is a Brown wire at the boost sensor which should have 5 volts w/key to on. Check the voltage of this wire w/the AFM connected and unplugged and see if it is the same or 5 volts unplugged but 0 volts w/the AFM plugged in. If this is the case then the AFM is shorting out the ECU.

 

I do want it connected... just not sure where it goes from there. looks like one side goes to the intake manifold, (closest to firewall.) double throttle system diagram shows one side going through a time delay valve to a diaphragm(usually these are worn out?) other side goes to the manifold.

the car is N/A. would it still have a boost sensor? there is one connector, that is not connected to anything, 2 wires, (one is brown if i remember correctly) right after the AFM connector.
Previous owner had the port air solenoid connected to it... put that wire back were it belongs, but they took out all the Air intake system and put a cone on it.

 

The NA has a pressure sensor.

And using the advanced search feature found this in one minute of time. Focus on post #20.

https://www.rx7club.com/2nd-generati...ee-pic-783951/

 

thank you for that, i was three pages off in the guide, i just hooked mine up this way. using the other diagram, was a random second check valve throwing me off, that apparently was not connected either... sigh.

the pressure sensor is hooked up and on the side of the frame. boost =/= pressure sensor?

 

There is a Brown wire at the (Pressure) sensor which should have 5 volts w/key on. Check the voltage of this wire w/the AFM connected and disconnected. Should be 5 volts both connected and disconnected.
If AFM is plugged in and it shows 0 volts AFM is shorting out the ECU.

AFM Disconnected 5.00v
AFM Connected 4.98v

 

So, with the hoses hooked up you still have the same issues? And is your fuel check connector jumpered?

 

that is correct. no jumper.

the afm thing i tested a few times, each time connecting it would drop the voltage, not much as you can see.

 

The AFM should dictate whether the fuel pump should run after starting the car. That it runs w/o the AFM is perplexing. There is a relay located under the dash and just to the right of the steering column. It is Yellow and Black and has 3 wires on the top row and two on the bottom, one Black and one Brown. W/key to on test the top row far right wire which is Blue in color. There should not be voltage.

And the hose to the double throttle diaphragm should be capped if it is not connected to the diaphragm.

 

third time typing this... LOL
Tested the blue relay wire, No voltage key on.
Replaced TPS(since it had not been replaced like previous owners stated)
Set TPS
Cleaned Throttle Body
Replaced AFM(still runs disconnected)

 

88 mazda rx7 conv smell gas when shut off cant find any leaks not any in oil very strong any ideals non turbo high miles

 

You need to check pin 2B of ECU. Wire is Green and is in plug #2 bottow row far right wire position. W/the AFM plugged in and key to on it should read 4 volts. At the AFM itself while plugged in and key to on the 2 Brown/Black wires will have 0 volts as these are both ground wires and the Brown/White wires will read close to 5 volts.

 

2b of the ECU is a no read
Br/W = 5.0v
BR/B =No Value

looked up 2B so the AFM isnt talking to the computer if im reading correctly.
(update)
did a resistance check, from the green wire on the AFM to 2b on ecu... no reading
did a resistance check, from the center ground wire to 2b on the ecu and got a reading...

sounds like im pulling apart the wire harness?

 

The Green wire has a metal sheathing covering that wire. Perhaps there is a break in the protective plastic of the wire and the copper wire inside is coming in contact w/the metal sheathing. You could do a continuity to ground test where the meter is set to continuity and one meter lead to the Green wire and the other lead to a ground to see if the meter rings out or not. And of course the ECU plug housing the Green wire would be pulled as well as the plug from the ECU. And while you're at it you could do a plain continuity test of the Green wire.

 

while i was poking around, i found this... where is that supposed to be connected? hoping its related.

 

had the multimeter on ohms, so yeah continuity check, there was nothing from the AFM to the ECU from ECU to ground on the afm i did get a reading.

I didnt even realize my new multimeter had the audible continuity check.

 

If the pictured plug has Green/Yellow, Green, Green,White and Green/Black wires then it is for the cruise control actuator. In other words, not your problem. Your focus should be the obvious and that would be the Green wire.

If you pulled the ECU plug housing the Green wire as well as the AFM plug and did a continuity to ground on this Green wire and your meter rang out then this is a problem which you need to rectify.

 

alright, i'll work on that, hope its easy to find, supposed to rain the next few days so not sure how much ill get done on it. I appreciate the time you are taking to help out. good to know thats for cruise control too, since im supposed to have that... saw the solid green wire and wondered if it was a relay or something that was missing.

 

so.... that's not it, i didn't get the probe deep enough, i checked continuity on all five wires and they are fine, probably meaning i didnt read the voltage correctly(found out you can flip up the sides of the connectors very helpful)...
the ecu ground looks a little corroded i'm going to clean that up.

 

Then what did the voltage reading of the Green wire read.