Detbyron

PLEASE HELP!!!

The Problem -
TPS is reading 0V for both 3F and 3G (Narrow Range and Full Range). Actually, I am reading this from the PFC, so it is VTA1 and VTA2.

The History -
1) Before engine is warm the car would stall. After warmup the idle was about 1,600rpm.
2) Tried adjusting the screw on the front of the throttle body. Even with the screw all the way out (not making contact) the idle would stay at 1,600rpm.
3) Allowed engine to warm up (idle cam sepperates). Checked TPS VTA1 and VTA2 on PFC. Readings were "way off" for both fully closed and fully open.
4) Tried to adjust TPS. Could not get VTA1 and VTA2 within spec for both fully closed and fully open.
5) Bought a new TPS.

Replacement Procedure -
1) Did not warm up engine.
2) Removed old TPS.
3) Installed new TPS and adjusted to what visibly appeared to be the "middle".
4) Realized there was a black wire with a loop terminal unconnected and sitting by the battery. The wire went to my MSD6a ignition ampilifier. (Note - this probably got disconnected when I got my clutch re-built a couple weeks ago)
5) Connected ignition amp's ground wire to battery ground (removed all connections to battery ground for a split second).
6) Turned ignition to on. (Noticed that time on stereo was correct i.e. breaking ground did not re-set).
7) VTA1 and VTA2 from the PFC read 0.0V.
8) Pressed accerlerator to the floor; still 0.0V.
9) Checked TPS connector. It was in fully.
10) Started engine. Idled at 4,000rpm. Turned off engine immediatly!
11) Removed TPS connector. VTA1 and VTA2 read abot 4.9 ~ 5V.
12) Removed new TPS. Inspected for damage or anomolies. It looks ok.
13) Installed old TPS and adjusted to approximatly "middle". VTA1 and VTA2 read 0.0V when fully closed and fully open.
14) Removed connector from old TPS. VTA1 and VTA2 read 4.9 ~ 5V.
15) Decided to only do 1 thing at a time. Removed ignition amp's ground wire from battery ground.
16) Old TPS still reads 0V when connected and 4.9 ~ 5V when connected.
17) Removed all connections from battery ground for minimum 20sec and depressed brake pedal. This was to clear any error-codes.
18) Re-connected to battery ground (except for ignition amp). Still reading 0V.

Questions -
1) What should VTA1 and VTA2 (3F and 3G) be when engine is cold?

PLEASE HELP!!!

Notes - I have a shop manual and am aware of this procedure http://www.scuderiaciriani.com/rx7/TPS_adjustment.html

Zyon13B

I wouldn't read off the PFC, check the voltage at the TB connector. And check that you spliced the right wires.

Detbyron

Why not?
Are you implying that the readings that the PFC are displaying are not reliable?
Are you implying that the readings that the PFC are displaying are different than what it thinks it is reading from the sensor?
Even if I don't rely on the PFC's readings, it doesn't change the fact that my idle is at 4,000rpm (probably due to the 0V reading)

I plan on it, thanks. But I figure that it will probably be the same as on the PFC.

What wires? I never spliced any wires. Are you refering to splicing wires during installation of the PFC (which I did not do myself)? This would not account for why it used to work and has just recently gone bad.
Or do you mean tapping into wires (to read the voltage at the TPS connector). I have not done this yet, but plan on it.

Zyon13B

I'm not sure how the PFC is supposed to read in correlation with the actual readings. They might be the same, but I think its best to to the test the way it is in the manual. Yea, sorry, I mean't make sure you tap the right wires when checking. Also, I think the manual says to warm up the car till the AWS stops.

J.S.J

better to test from the source (tps) Each wire at the tps has a testable value. Doing that will provide you the health of the support wiring and the ECU one step later.

BlueRex

I too am experiencing the same situation.

I unknowingly displaced the tps while i was trying to remove that damn grey connector and threw the whole thing out of whack.

I get 0-.01 voltage readings when the car is off (not through the pfc but a multimeter).

When I had the Throttle off i placed the tps in the middle as to get a good starting point for adjustment and started the car and got 4k rpms. I found that if you leave the tps in a relaxed position (not forcing it towards the middle) the idle atleast dropped to 3k rpms. I let the car warm up a little and did some voltage checks and got some readings way off spec. Before this my car ran perfectly fine. While I had the manifold off I eliminated my aws, but I doubt this had anything to do with it.

Im going to try and figure this whole thing out tomorrow. I'll let you know if I find out anything useful.

J.S.J

Guys,
The harness/connector needs more than just a 5V reference at the Tps, I'm sure you guys know that but lets look at the wiring now I don't have my manual in front of me but this is the general idea of how the sensor should work. Yes it takes the 5 volts in from the ECU and it enters the tps, then there "must" be a ground wire on the sensor that leads back to the ECU. So one of the wires at the connector has to go to the ECU and ground internally there. That means theres a couple of things that could be skewed in that circuit which could cause the readings to be absent. 1. If the wire leaving the tps is broken or one of the grounds in on the ECU is damaged or disconnected. 2. The wires are fine but the terminals which look fine are in fact spread to wide and tho they connect there's no contact. Check this stuff with a volt meter or ohm. A volt meter could be used with the ignition on and the tps sensor connector disconnected. Set the meter on a scale over 12 volts maybe the 20 volt scale. Connect one volt meter lead to the 5 Volt reference wire and one to each other wire in the sensor connector one at a time. The one which reads about 5 volts or 4.9 or so is the ground. There must be a wire in the connector which has the job of sending the actual sensor reading back to the ECU. This normally when connected to the 5 volt reference terminal on the tps will read about 1/2 or so surely not 5 volts. Guys this stuff is not hard you just need to check the quality of the wiring. I am assuming you guys dont have the stock ECU in there and are using a Power FC system with that in mind and I am a bit new to the rx7 and don't have a PFC I do understand how the computer controls work. If you simply jumper with a hard wire the 5 volt reference at the connector to all the connectors terminals at the tps one at a time and look at the reading of the PFC it should register a reading. If you hold it on/jumper-ed for a second or two thats plenty of time to see if the system is wired correctly if no change is seen its likely the wiring is skewed between the connector and the PFC. One step more is to jumper the terminals at the PFC if the voltage reading reacts then you know there a skewed wire up stream in the direction of the tps. If nothing or no reading changes its likely the Pfc is skewed. The 5 volt reference is in the milliamp category and in my judgment wont damage anything. I have never seen an ecm/ecu damaged doing this. Have fun and good luck

Zyon13B

Guys, the car must be warm before you adjust. If you don't like the high idle till it warms, There's some things you could try. Disable the AWS some how, plugging the hose from the intake elbow is one way. You could also mess with the air bleeder screw when the elbow is off( which I recommend taking off when adjusting anyway) and you have the hose plugged. It's real simple, the engine can't idle high if you cut it's air supply. Then, when its finally warm, stop the engine, turn the key back to on, then measure. The way I tapped the wires, I used two staples, bent them straight, then inserted them into the wire boots to touch the metal connectors while the connector was plugged in to the TPS.

BlueRex

Well I figured this problem out.

It just wasn't sitting with me right that there was absolutely no voltage while the car was cold plus I was getting the CEL saying there was no reading from the sensor period. I at first attributed this to the loose position I had the TPS in. But there still should have been some voltage even though the fast idle cam was affecting the voltage. I removed my throttle body and TPS. I turned the throttle body and watched how the metal piece inside where the TPS attaches turned (clockwise). I then realized I had put the TPS on wrong

The two plastic pieces that make contact on the TPS side were making contact on the wrong side. I had mine making contact like this:

= is the metal piece that rotates inside the TPS connection point as the throttle body turns.

[ is the plastic connection piece on the TPS making the contact with the metal piece.

wrong way: [= when throttle opens goes to this [ =

When it should have been making contact like this:

right way: =[ when throttle opens still makes contact and winds the wire on the TPS tighter thus increasing the voltage

Thus when the throttle opened there was absolutely no contact being made as the metal piece rotated away from the TPS and therefore explaining the no voltage. Just take off your throttle body and take a good look at the TPS and how it works as the throttle opens. I did this and the TPS works great now. No check engine lights no 4k rpm idle. I let the car warm up completely and tested the voltages and they are all within spec.

Glad this nightmare is over.

Detbyron

You gotta be f'ing kidding me! I will check this tonight!
I thought that I had looked at this. And besides, [= seems intuitively correct as opposed to =[
Still does not make sense though that when the sensor is fully relaxed that the reading would be 0V.

BlueRex

That's exactly why I had it backwards, because when you look at it it just seems like common sense that the sensor be put on where the contact would go like this: [=. But like I said if you remove the throttle body and watch how it works as you open it you will see what I mean.

This explains the 0 volts because the throttle isn't winding the wire tighter like it should be and thus the there is no voltage. This also explains the high idle since the metal piece on the inside is rotating away and with no increase in voltage the throttle just opens wider and wider to try and compensate. Trust me if you just take your time and look at it you'll see what I mean.

Jason

Detbyron

Yup.

I checked it last night, and I had it backwards (instead of taking off the throttle body or elbow, I took off the TPS to watch the "tongs" rotate).

I still can't get it adjusted properly, though, so now I'm thinking that my original TPS was ok (oops, $130).

Yesterday after installing the TPS correctly, I set it to approximatly the center and went for a drive to warm up the engine. It felt great (all of my "drivability" issues were gone, like backfiring, slight bucking, quick rev drop when clutch disengaged, and lack of power). So I thought to myself "wow, it's gonna drive AWSOME after I adjust the TPS properly!!! So I tried to adjust it, but no matter what I can't get it in range.
Oh well, at least it's running again! I guess I go some more work to do.

THANKS BLUEREX!!!

BlueRex

No problem.

And what I did to make sure that the TPS doesn't get too far out of adjustment again was mark the new hex nuts I put on and the throttle with a permanant marker so that way if the TPS ever gets moved again I just line it up and all the voltages will be within spec.

BTW you may not be able to get all the voltages within spec because you are using the PFC commander to read the voltages. I read that there can be up to a .2 voltage difference between the commander and a multimeter that is tapped in directly to the wiring.

Jason

J.S.J

Good Idea. See we screw up something (innocently) and learn a Sh*t load of things about how things really work. There is a big up side to screwing up now and then. I should know! Good going

Detbyron

Yeah, you know, I'm not really surprised I guess. I would assume that the voltage drop would be due to the wire length (and then possibly voltage drop within the ECU). I believe the service manual, which we are refering to for the voltage values, says to measure (using the SST of course) at the ECU, not at the sensor itself. So, there MIGHT be a slight difference between reading from a multimeter at the sensor and using the SST.

BlueRex

Haha, so true...

That's also true. But I decided to follow Chuck Westbrooks write up and measure directly at the sensor and since the values I got from the multimeter were almost in the middle for all of them I'm not too worried.

Good luck fine tuning that TPS and thanks to J.S.J and Zyon13b for attempting to help us.

Detbyron

Since I couldn't adjust the TPS within range when I was reading off of the PFC, I decided to do what ya'll were recomending, and I used a multimeter to measure at the sensor.

This was my results -

WITH MULTIMETER
Wire Closed Open
3F 1.085v 5.02v
3G 0.491v 4.35v

Woo-hoo, close enough, even though 3F aka narrow range aka 2nd from top aka VTA1 was out of spec when fully open.

After I got this adjustment, I read from the PFC.

WITH PFC
Wire Closed Open
VTA1 0.47v 4.34v
VTA2 1.06v 4.97v

SPECIFICATION
Wire Closed Open
3F 0.75-1.25v 4.8-5.0v
3G 0.1-0.7v 4.2-4.6v

I think I'm going to post these results in the PFC section. I had done a quick search and never heard of people getting readings this far off.

Anyway, thanks again to BlueRex, J.S.J., and Zyon13B.

Zyon13B

Good work guys. I have a PFC, when I get time I'll check what mine says. I just adjusted mine by the connector not to long ago so I know thats right, I'll see if my PFC is off too.

gracer7-rx7

iTrader: (16)

Thank you very much Blue Rex for posting this!