1986 2nd gen won't run at wot
 

1986 rx7. Na.

Bought car for son for 600 bucks. Drove for a couple months, but then started running on 1 rotor on wot. Checked compression in motor low and was consuming oil.

Rebuilt motor with all new seals and good used parts. Turbo rotor housings. All smog has been blocked off. No egr, noir pump. Removed rats nest except for orange fuel pot.

Redid all grounds, before rebuild had injectors cleaned and flowed

If very light on pedal can get car to rev, if anything approaching 50 percent or more throttle and it won't go over 3500 rpms bucks sputters runs on 1 roto...

Have a bunch of Spares so other than regrounding the car. Changed ecu no difference, changed afm no difference. Changed leading coils no change. checked pins at ecu for primary and secondary injectors all 12.1 volts.

Checked tps got car warm adjusted to 1 volt. Checked pressure sensor at sensor and e cu 3.6 volts.

Changed fuel pump and filter no change

Will check injectors for impedance and will order pill for pressure sensor...anyone else have any ideas?

Test the AFM to make sure it's operating within range.

Also, test the full sweep of the TPS to make sure it is smooth and there aren't any dead spots.

There are no dead spots but the whole linkage and TPS just doesnt seem right. Previous appears to have removed a bunch of stuff.. It does pass the 1.0 v test when warm and sweeps through to 3.6 v at WOT.

I do not have an orifice in the pressure sensor.... ordered from mazdatrix.

It seems like the secondary injectors do not fire, it is not the dreaded hesitation but a complete shutoff like a fuel cutoff when you hit redline..only around 3500.

These are cleaned and flowed injectors...would the wrong impedance cause the secondaries not to fire?

Thanks for the help!

The TPS should go to about 4.5 to 5 volts when the linkage separates from the TPS plunger.

Thanks again Satch will try to understand that and adjust.

I tried another AFM that I have as a spare an no change. I will test the AFM to check for deadspots.

I will also rechech the tps....so dead spot means no volt reading..

I have been searching and reading tons of stuff almost too much. My thoughts are maybee a sticking AFM...

Maybee a bad engine wiring harness at the engine.

You would need an analog volt meter to measure for dead spots as the voltage needle would be jumpy if there was a dead spot otherwise the needle would slowly and w/o interruptions climb higher. A digital meter will be too sensitive to show anything meaningful.


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The shame is I have an engine signal monitor but it has Miata ECU adapters. If I could find 2nd gen rx7 adapter I could get this this thing figured out.

You might want to add an additional ground as suggested by Mazda for the early S4's due to a faulty ground to the AFM. They suggest to add a ground to the existing ground at the Pressure Sensor and connecting it to the engine. There are four wires at the sensor. One has 12 volts w/key to on, one has 5 volts w/key to on, one has about 3 to 4 volts w/key to on and the remaining wire is the ground wire. The bolt at the coolant filler neck is a good spot to tie into.

Will try that ground.....taking a break on the kids rx7 to go run Spec Miata at the NASA race at AAA Cal Speedway. WIll get back to the RX7 next week and weekend!

Thanks for the help

If you want to check out his spec miata racing you can check out at go racing tv.

My son is in car #41. He is in his second season of racing. The racing starts 5 minutes into the show

NASA’s California Crown 2012 – Spec Miata Race | GoRacingTV | Racing Videos and Racing News!

Have a great weekend!

So update... changed the CAS because I had a spare, which helped a ton... It now operates on the secondaries and it has the normal 3800 rpm hesitation!

Rechecked the TPS and the reading is at 1000 but jumps to our of circuit when I slowly go through the sweep! It does read 6.0 v sometimes at the stop and other times 4.5...

Ordered a new TPS and I think we have got it solved. Thanks Satch and Aaron. Really appreciate your help

Slowly but surely. The additional grounding of the Pressure Sensor "should" help w/the hesitation.

We did the grounding also. I'm sure it helped....

Replaced the TPS almost there....I noticed when we set it and checked the volts through the sweep at WOT it still only reads 4.5V? Not sure if this matters or not, but curious.

We also put the orifice in. SHould it be closre to the manifold or the pressure sensor?

Thanks again, we are gaining on it.

The orifice is close to the Pressure Sensor and 4.5 volts at full sweep at the TPS is just fine.

So she still falls on her face at wot some of the time.......real confusing. Made a code checker today and got air pressure sensor. Changed afm. Helped some. The only thing I havent done or checked is to replace the engine harness?

What code was thrown as in the specific number? You're using "air" and "pressure" together which is a bit confusing. Is it one of the air temp sensors, the Pressure Sensor or the Atmospheric Pressure Sensor? And did you install the orifice with the little hole closest to the sensor or in the opposite manner as I think it makes a bit of difference although I can't remember which is the proper way.

Code is one long light and pause one short light and pause......

Code 15 - Intake air temperature sensor.
DCC1: L P ... (1 long light ... long pause ... repeat)
DCC2: S P ... (1 short light ... long pause ... repeat)
Fail-safe mode: Maintains constant 20C (68F) command.
Comments: This is located on the intake air pipe just prior to the throttle body.

This is a 1986 so I thought the intake air temp sensor was in the air flow meter. I also don't think it can go into fail safe mode as this was not available in a 1986??

Going to double check ecu #

Since you have an NA that sensor is located on the driver's side of the engine (turbos are located in the intake tube) and has but two wires with one being Black and the other Green. Make sure the plug is solidly connected and at pin 2L of the ECU the reading w/key to on and engine fully warmed would be 1 to 2 volts.

Once again thank you Satch. I will look for it and test it.

Found the plug wire is grey(probably faded black and green) Found the sensor and plugged it in. No time for test drive, will try it again tonight.

Does this sensor cause drivability issues? Here is hoping that it does!

^ Not sure. People tend to believe the one in the AFM plays a more vital role but who knows.

The good news is no more codes! Bad news is it is still running poorly above 4000.

I will go back to basics now looking at fuel and spark. Did the testing previously on the ECU, but will check again to see if secondaries are working...

sounds like injector wiring, poor power feed from the EGI/main relay.

try reading voltage at the ECU for the injectors and see if it dips or if one or more is considerably low while under hard loads.

Thanks Rotary evo. My bet is injector wiring. the engine harness is about 400 bucks from Mazda. I am scared to go with used>> any thoughts..