... using the 2 LED light method; I understand that part just fine. I now have a one LED light TPS. What I'm not clear on is the resistance test with the Ohm meter. Should I be measuring resistance at the TPS test connector (where you plug the lights in), or at the TPS itself up on the Throttle Body?

I know this subject has been beaten to death. I apologize. I'm a 4-month rotary owner and I have searched and searched (FSM, this site, FCS3.org, etc. ad nauseum). I thought I had it figured out buy I guess not. Also, if the resistance is found to be "out of spec" closed and wide open throttle, what do I do? Replace it? Thanks for the help in advance.

Josh

 

I don't know what car you have but this is what I did on mine.

Hope it helps.

http://img.photobucket.com/albums/v2...her/junk21.jpg

 

Sorry. 87 NA.

 

Warm up engine.
Located TPS and unplug it from the rest of the harness.
Use DMM probes on BLACK and GREEN wires.
Adjust to 1.0k-ohms - slighter lower is better than over.
Open throttle gradually, and make sure it sweeps smoothly up to 5.0k-ohms.
If WOT is over 5.5k-ohms, the TPS needs to be replaced.


-Ted

 

So I'm still working on this this crazy TPS ... the tester light method works fine. I can turn the adjust screw and get a one light reading (as well as a two light and a no light reading). It's set to one light now -- engine was completely warm and off; no accessories were running.

Then, my Waterloo evidently now, I go to check the resistance with the DMM. I unplug the TPS from the harness... and insert the DMM probes in the BACK of the TPS connector (the part that connects to the harness) and I get a good .99~ reading in the idle position.

Then, I attempt to move the throttle to WOT. My DMM will do one of two things depending on how fast I move the throttle. 1) It will go DOWN to about .45~.50 K if I move it very slow. Or, 2) it will just read .0L if I go a little faster. I thought it was supposed to go UP to approximately 4-5K.

Is the TPS bad or am I dumb and can't use a DMM???

Josh

 

Is it set to resistance of the little omega symbol?


-Ted

 

This is the multimeter I have... Radio Shack DMM . The dial is set to "OHM 20K"

 

Okay, the DMM is set right.
If the resistance is indeed dropping when you check travel, I'm afraid the TPS is not good.


-Ted

 

That's what I figured... I'm having some other problems as well that might indicate this TPS needs to go. rough idle, particularly during warm up, bouncing idle. I set it with the lights... then jumper the intial set coupler and set the idle... never fixes the problem.

So, if I'm setting the TPS with the tester lights and the TPS is indeed bad, then my current setting probably isn't correct.

Okay, enough of this. I'll replace it. Anybody have a "good" TPS they would like to sell? Test it before I buy it.

Josh

On a completely different note... I did notice jumpering the initial set coupler today eliminated the bouncing idle. Just seems overly complex. haha

 

i have no clue whats happening here, could someone please tell me what the TPS does, where it is, and what the advantage of adjusting it is please?

 

It tells the ECU the throttle position.

For example if you lift your foot off the throttle, the TPS tells the ECU that the throttle is closed, so then the ECU cuts the fuel so that the motor doesn't get an overly rich mixture.

A mis-adjusted TPS will lead to stalling at lift throttle, or poor idle, or surging idle, etc.

 

damn, i do have bouncy idle, when my engine is cold, my idle jump up and down constantly until fully warmed up. I guess i need to to this then!

 

The TPS has two primary responsibilities.

1) transient throttle - mashing on the gas pedal will automatically cause the TPS to signal 100%
The stock ECU adds more fuel to compensate for this sudden transient.

2) fuel-cut on throttle lift - by cutting the fuel when you lift off the throttle, this allows the engine to "wind down" faster, and to prevent fuel burning (popping) in the exhaust


-Ted

 

Before you run out and spend some big bucks on a new TPS, try measuring the resistance with the DMM's dial set to 2K instead of 20K. This will give you actual readings instead of decimal readings. I also have a 87 N/A and I'm struggling with my TPS too. If I set the TPS to "one light on", the resistance measures somewhere around 1600! If I set the resistance to 1000, there are two lights lit. Go figure....

 

Not necessarily...
I believe the DMM settings are maximum ranges, so the readout should still be "1.000 k" even if it's set to 2K-ohm or 20k-ohm settings.


-Ted

 

Chuck -> Yea, same here. Using the lights (DMM says 1.3~ ohms), the car runs well. But if I use the DMM to try to get a 1 ohm idle setting, I end up cranking the screw clockwise about 2.5 turns (approx.) and the car stumbles, bounces, and gives me a two light setting... overall, sounds like crap.

Ted -> I get the same readings on 2k as 20k. Think you're right.

 

is there a good writeup + pics to doo this 2light method? thx

 

Of course.

Factory Service Manual - pg. 4a-50

And,

RacingRotary.com/TPS.htm

 

I read a while ago, possibly back in July/August about a guy who was having problems with his TPS, from memory he just disconnected it, he believed that his ran ok without it, apart from backfiring and running roughish when cold. I serached for the write up he did but couldn't find it, anybody remember?

 

On the US spec models on everyone I have seen that it will run for a while with the TPS unplugged, but eventually have run and power problems.

 

Well, tried it again today... persistent Good news I guess... well, almost. I disconnected the TPS connector from the harness. Tested at the back with the GREEN and BLACK wires. My Idle resistance was around 1.3 ohms (out of spec by .3 ohms right?). This was after I had set the TPS with the tester lights. So, I adjusted it down to exactly 1 ohm. 2 turns (approx) of the TPS screw I believe.

The progress today came when Dad was pressing the accelerator. Instead of going bonkers today, the DMM went smoothly up to 5 ohms. Yay. WOT is within spec. I think I just may have not been getting a good connection with the DMM contacts.

Now, I guess the real issue is: If you set the TPS with the tester lights and then get a reading of 1.3 ohms, is the TPS bad? And ultimately, is this contributing to my surging/hunting/bouncing/ idle during warmup?

My guess is yes, but I don't think it's the only culprit. When I jumper the intial set coupler to adjust on top of the throttle body, the bouncing goes away -- completely. This leads me to think it's the BAC as well. I will clean it and test it tomorrow.

Also, could dirty grounds be causing my 1.3 ohm TPS resistance reading at idle?

Thanks for the help everybody... this is a good learning experience!

Josh

 

ok so i have a question for u guys. my car idles fine i can rev it up til whatever fin when i put it in gear and rev its fine but when i actually accelerate the car hesitates/bucks cuts off then turns back on...is this, could it be related to tps?

 

sorry to ask dumb questions, but once the tps harness(es?) are disconnected, you measure the resistances from the TPS side or the harness side? either way, why would it matter whether or not the car was on if you've disconnected the tps? unless there are two plugs and you only unplug one.. (cant remember)

 

You measure from the back of the TPS side of the connector... not harness.

 

figured as much.