i tried unplugging the TPS and it does the same thing. also took the TPS off the mounts and pushed it in and nothing seemed to be happening, also, i tried to check the resistance of the tps and wasn't getting any readings whatsoever (im an electrician so i know how to use it :p)

thanks again

 

no one has any idea of whats causing this??

 

Try checking for voltage on the Green/Red wire w/key to on after the car is completely, and not partially, warmed up at ECU pin 2G. It should read 1 volt at idle and increase to about 4.5 volts w/the TPS plunger fully extended (basically at 3k rpm or higher).

 

Great. I'll try that. Thx satch. I'm kinda at my wits end haha

 

RotaryHeads.com - 2nd Gen RX-7 PDF Technical Manuals FC3S

Open the FSM, section 4A. Do the procedures listed on pages 4A-77 through 4A-79

 

Thank you I'll get on that. And satch where do I find pin 2g? Is that on the ECU itself or do I unplug the TPS to check?

 

Pin 2G will be on the ECU.

You can also just backprobe the connector with everything still hooked up.

The absolute best way to actually set the thing is via the light method. See http://web.archive.org/web/200902080...odes/main.html . Shows how to make one for a couple of bucks.

 

Okay so I warmed it up. Back probed off the TPS.. No voltage readings.. So I put the act probe on negative of my battery. And Back probed again. All three terminals are at 5 volts on idle. I Rev it up and it stays the same.. Coukd this be my issue?

 

Yes.

There should be ground, +5v signal (varies), +5v reference (always 5v)

+5v on all 3 says dead short across the TPS.

The TPS is just a simple pentintiometer .

 

Ahh that's what I thought.. It's just odd that it's sporadic.. Like I can drive the car around for 20 mins and it's fine. And then randomly it will act up. But u suppose replacing my tps will at least help the problem. Thanks for your help!!

Also. When I was checking for resistance across the female end of connector. I wasn't getting anything across ground.. Unless I put one lead on negative of battery.. Possible that I have a grounding issue as well?

 

Not suprising, a little bit of heat can expand things just enough to make contact again.

The male end should have the ground, as far as I can recall. The TPS doesn't ground directly, it grounds all the way back at/near the ECU.

 

ahh yeah that makes sense then. thanks so much!

 

If you were to unplug the TPS and measure the ground wire of the emission harness (plug on the opposite side of the TPS plug). Ground wire on an 86 is Brown/stripe but it is not the Br/W wire as that is the voltage reference wire. So you have G/R, Br/W and the ground wire.

Another thing to check to make sure your problem is limited to only your TPS would be to check the 4 wires at the pressure sensor w/key to on and sensor plugged in. B/W will have 12 volts, Br/W has 5 volts, Br/R has between 3 to 4 volts and the last wire is the ground.

 

ill go ahead and check that out now.

 

Measure the ground (TPS)w/key to on.

 

Yup. All those voltages seem to check out.

 

Ground to which pin?

 

The negative battery terminal. The key is to sense voltage on the ground wire which should not be there, but since the ground at the pressure sensor tested properly then the ground at the TPS should measure the same since it shares the same ground.

 

Okay. Yeah 5V on the power and 0.1 on the other two. With tps D/C and key forward

 

Now it's time for you to make a new TPS appear.

 

joyyy.. part source, $420
im thinking rock auto. their on there for like $200

my friend has a T2 motor.. could i pull it off that? im thinking not..

 

Take a multimeter with you to a u-pull-it type junkyard and test the resistance of any you find. There's thousands of S4 NA's in yards right now.

 

Right? I just got a spindle and it was off a junker but the spindle is in great condition

 

Well I got one from a mod off the forums. But I was recently at the largest yard in my area and no rx7s of any kind but thank you!

 

Well... i got a new TPS, and the idle is no doubt smoother,

however i will still occasionally get a huge hesitation while driving, and then it starts to run rough (like the video) but is not as bad and does not last as long.

So my thoughts are it was the TPS along with something else?

any more suggestions? thanks again everyone