Cpu says TPS is bad, DMM test says its good. Car gurgles.. Hmm...
 

So what do you do when the cpu says code 6(TPS), and you test and adjust the tps and everything is just the way it should be. But I am still having this problem where the car backfires on decel and causes some surging. On rare occasion the car bucks on accel and it'll go into what acts like limp mode even though it's an S4 turbo. And I read that the s4's dont have a limp mode. I really want it to run smooth! PLease help!

Go to pin 2G and with a fully warmed up car look at the input to 2G. It should be approx 1vdc. Then with the engine off, step on the pedal slowly while watching the meter rise and fall. Look for *opens*.

THE CAR HAS TO BE HOT WHEN YOU SET THE TPS (There's ways around that, I know). But do it with the engine hot.

If you ohm'd the tps out, you should have been looking for open or dirty spots when you go full open to full shut. THAT is why the manual has you test the TPS using a ohm meter. Your looking for bad spots. And if you set the tps using the ohms method, the engine should have been fully HOT (I know there's a way around that).

Backfiring when letting off the throttle is an indication that the tps isn't seeing full off IMHO.

Hmmm, okay... the fc3spro site is what I used to tell me how to test the TPS. I am not sure what pin 2G is. And, I did do Ohms when I checked it. I hate to noob you Hailers, I know you have better things to do but, I am new to using the DMM. The FC3s site said nothing of VDC. it says 1k ohms at rest up to 4-6k ohms on WOT. I had no blow opens. And it does not identify the wires except by color.
I haven't found the TPS adjusment section in the FSM, perhaps there it will identify 2G for me.
So you think this may be it?

Thanx.

Hmmm, I can't find wire 2G.. I assume thats in the TPS? I checked the FSM, nothing there...

it's 2g at the ECU I believe....

Is the ECU under the passenger floor plate?

yes

Giggle, thx... I'll go diggin there...

Jeese, where in the FSM, or how can I identify wire 2g in that mess?

Well I think I found it, bottom row, 9th one over from the left, its green, and I have no Idea what to do with it... I set my DMM for 20 VDC and tested all ways that I could imagine and got no response from anything... sigh...

Anyway, I am postive that the TPS is perfectly fine. But I keep getting code 6 (TPS), so what does this mean? I used to use the lamp method to adjust the TPS. Did I perhaps fry something when I did that?

Middle plug on the ECU. You count the sockets with the plug connected to the ECU and you count from the far right top...and the next the far right bottom....then the next far right top ....and the next far right bottom and on and on and on in a up/down method until you have run out of pins/socket.

So 2G is on the top row, fourth one on the top row from the far right. It's the same color as the other end of that wire connected to the TPS.....Green/Red.

Put the meter on Volts DC. Put the negative lead on a ground like one of the studs that hold the ECU in place. Put the positive lead of the meter up the backside of pin 2G. Use a sewing needle or paper clip to gain access to the backside of the pin 2G.

Idle the engine. The meter should read approx 1vdc if the engine is hot. Something like .95 vdc or 1.05 falls in the approx area or the word approx. Hot engine please.

Download the FUEL section of the FSM. The plugs are shown there as well as the wiring diagrams in the Wiring Schematic area.

You'll get a tps code on a series four if the wiring is not intact. Like a open wire b/t the ECu and the tps.

So, if there is a break in the wiring, I'll get something other than 1vdc. And then what, follow the wire up into the engine to determine the break?

Attached is a jpg. At the bottom should show the three plugs on the ECU. Your looking for the middle plug, fourth wire from the top right. Pin 2G.

With the key to ON it should show apporx 1volt dc. If it's off a bit then just adjust the screw on the tps til it gets close to 1 vdc. Engine hot.

Then with the engine off, and the key to ON, slowly push the pedal and watch the meter voltage rise as you depress the pedal and the voltage go down as you slowly release the pedal. It's hard to see on some digital meters but there should not be any OPENS as you go fulll open to close and vise versa. And say your depressing the pedal, the voltage should rise but never fall as you depress the pedal. And vice verso as you slowly let the pedal up.

I Dled it this morning and just found the section you attached. I read in there that it's failsafe is to "maintain constant 100% (approx 18 degrees) command. So I guess that means it would be running rich at all times in case of malfunction. I.e. Idle and decel.
I will check this tomorrow using this method.
Update to be posted. Stay tuned! And thanx Hailers....
again....
:)

Well, I no matter what I do, with my DMM set to 20 DCV all I get is 0.02 reading on wire 2g... No matter what the gas pedal does or whatever I do to the TPS. So does this mean I have a break?
Funny thing though, when I stuck the needle into the back of 2G the idle changed and seemed to smooth out while my fingers were touching the needle... Hmm...
All of this done with a hot engine.
Whatcha think?

It could be a broken wire b/t the tps and the ECU pin 2G. The Green/Red wire, forth pin from the right, top row, middle plug.

The tps has to have its connector connected when you do this.

Meter on DC volts?

Meter negative lead on a good ground?

Try this with the key to ON. Go to the small plug on the ECU. Back probe either pin 3I or 3J. They are the pins on the far left of the small plug on the ECU. They both should have 12vdc when the key is to ON. If you see 12vdc on either, then you know the meter is good and the ground point that your using for the meters negative lead is indeed a good ground.

Sooooo, if you do see 12vdc on either of those and nothing on the 2G, then you do indeed have a open wire b/t the tps and the ECU pin 2G. Hard to imagine since there is no connector b/t the ECU and the TPS plug.

Again, the tps plug has to be connected to the tps when you do that. Try the above and write back today.

Roger that, I am getting on it now...
(A few minutes later)

OKay, confirmed... 12v on the far left pins... still getting just .02 on pin 2g.. Where could the break be? hmmm....

gOOD.

Now go back to the TPS plug. Pull it apart. On the HARNESS side of the plug, put your meter in the socket with a Brown/White wire. Turn the key to ON. You should have approx 5vdc.

If you do then: Put the meter on ohms and the negative lead of the meter on a good ground. Put the positive lead in the socket that has the Brown/Black wire in it (it could be pure black if its a 88 car). You should read something like .1 to .5 ohms.

Tell you what, if you have the 5vdc on the brown/white wire and have a ohms reading of approx .1 to .5 on the brown/black wire then do this: Put the TPS plug back together and turn the key ON. Put the meter negative lead on a good ground. Put the positive lead in the back of the Green/Red wire and see what you read on the meter. It should read approx 1vdc or so.You might do this first before the other things above.

cool, gimme 15 mins...

Ahhh, Hailers... I suppose you understand that when you are in the process of learning things, that from time to time little moments come that remind you of how dumb you really can be... *GULP*...



Here it comes... are you ready?













I wasn't.....














I had the (Green) testor plug connected to the TPS this whole time and not the white plug.
Yes there it is.. I am indeed a moron.... Sigh... I plugged in the white plug and my car stopped giving the code 6.
Learning can be so painful sometimes...
Well regardless, I wouldn't have discovered this if it were not for your help. My god, I made my wife let me buy a new s5 turbocharger because I thought I ported the waste gate on my s4 poorly. I took my intake and exhaust apart 3 times each to try and find this.

I'll tell you what, I think you are over 21... PM me your mailing address so I can send you a bottle of wine. Because this is indeed the dumbest thing I have done in my 6 years of Rx-7 ownership. This deserves a celebration!

Lmao...
sob, sob...

lol...

omg...

sigh...

That's funny. It falls under the heading *Stuff Happens*. Not a biggie. Have fun.

haha.

congrats on the solution of the problem, however!

running alright now?

Well, I just finished putting it all back together... So if you'll excuse me.. I have some much needed spirited driving to do...
An update will be coming...

Well, drives like a bat out of hell.. There is no more backfiring yay! So, I expect that I won't be having those breakdowns that it seemed to cause before. Only thing going on now is the age old surging Idle. I believe I tested the BAC a year or two ago and it came out as being bad. I will check it again tomorrow and look for your stuff (Hailers) on the BAC. I know you are the BAC master and I too prefer to have one regardless of my mods. Interesting thing though, I unplugged the BAC with the car running and nothing happened. It continued to surge just the same. 1200-1500... Then with the BAC unplugged, I turned on the AC and it smoothed out... Vac leak?