>>but if the sensor is just plain shot, does it give 0 V or erratic readings?

dunno, both maybe possible however i think if it reads 0 you will get limp mode or somthing like that.

If it reads zero you are probably not testing it correctly :-)

 

thanks

anyone have experience testing a shot TPS?

 

The TPS is just a variable resister. Based on the electrical diagram and not having torn one apart (yet). It simpley allows different voltage drops depending on the throttle position. Very less to no drop in resistance at wide open / to alot of resistance at idel. IF a winding is worn or open the resistance will have a dead spot ( no resistance) then come back when the dead spot is passed in either direction. Also if resistance is increased by bad contac to the windings, the position (resistance) will read to the ECU a false position. The ECU relies on the TPS to tell it where the throttle is. How this is interpited by the ECU is the unknown. The ECU is designed to cause certain things to change as we all know due to alot of inputs (sensors) at alot of different RPMs. What it does at idle mostly concerns emissions. At wide open its trying to prevent the engine from exploding. So depending on what is wrong with the TPS determines the way the car runs or doesn't run or runs then cuts out and dies.

 

yeah that's why I think it's shot, the resistance is out of spec and adjusting it doesn't help...getting a new one tomorrow (thank you, Fritz, saved me $$)

 

K, guys, I have a PowerFC w/ Commander and have this problem on my FD. Can I adjust the TPS with just the readings on the Commander or do I still need a volt meter?
I did some research and somewhere it said that the VTA1 and VTA2 in the ETC menu mean something, so today after I drove the car to work, I shut it off and got these readings.
Close Throttle: VTA1=.49 VTA2=1.07
WOT: VTA1=4.37 VTA2=4.97

Can you guys tell me anything about my car with these numbers to do I need the volt meter? Also, what are the correct numbers supposed to be? Thanks for everyones help on this!

 

no, the Power FC makes the job much easier, just read straight from the Commander

VTA1 = full range sensor
closed throttle = 0.1 - 0.7 V
WOT = 4.2 - 4.6 V

VTA2 = narrow range sensor
closed throttle = 0.75 - 1.25 V
WOT = 4.8 - 5.0 V

you're good...mine is almost identical (now that I have the new sensor installed and adjusted)

 

The mechanic thinks he has finally traced the intermittant bucking and surging and engine dying going downhill to an intermittant bad fuel pump. Has anyone else had such problems traced traced to the fuel pump?

 

get a fuel presure gauge on it, run some tests, and you will know if its the fuel pump

keep in mind it may be the connections to the fuelpump and not the fuel pump itself, that is why its good to check the coltage its getting at both high and low voltage conditions

 

New plugs, Fuel pump and regulator replaced, voltage regulator replaced, ?dash pots? freeded up, TPS adjusted again, ... and it is STILL bogging down under light acceleration, still some oscillation; and also occasionally dies going downhill (automatic trans), which can be exciting if you don't notice it.

This bird has been a lot of trouble this summer!

 

The bogging, hunting oscillation, hesitation and surging at light to moderate loads is still going on. The mechanic seems to have given up on finding a cause, unless it is sticking injectors. Extra fuel smoke on startup makes him suspect the injectors are leaking into the chamber on shutoff, and maybe when it is running. It might be only noticable under light loading. He poured in some Techron and suggested I do the same for a few tanks.
I don't have great confidence that engine cleaner will fix the problem.
Any other good ideas? Would it be worth it to pull and clean or replace the injectors?

ciao

 

I am assuming that when you test the voltages between the two wires that closed is obviously with the throttle completely closed and that open is where you manually open the butterflies by hand at the throttle linkage as far as you possibly can go and then record that reading. Is that correct?

I'd like to know what would be the effects of doing this adjustment without the car being started and warmed up to normal operating temps.., incorrect readings?

Also my last question is in my case I am only getting the same reading whether I rotate the tps, or open the butterflies simulating WOT. The voltage does not change for either probe no matter what I do to the tps. I get a constant .05v for the second to the top wire, and 2.5v for the bottom wire.

 

>>I am assuming that when you test the voltages between the two wires that closed is obviously with the throttle completely closed and that open is where you manually open the butterflies by hand at the throttle linkage as far as you possibly can go and then record that reading. Is that correct?


yes, or just have a buddy push the gas pedal to get the wot reading :-)

>>I'd like to know what would be the effects of doing this adjustment without the car being started and warmed up to normal operating temps.., incorrect readings?

none...the cars temp or ambient temp have no affect on the voltage reading


>>Also my last question is in my case I am only getting the same reading whether I rotate the tps, or open the butterflies simulating WOT. The voltage does not change for either probe no matter what I do to the tps. I get a constant .05v for the second to the top wire, and 2.5v for the bottom wire.

you are either doing the test wrong or your tps is totally broken :-)

 

The only reason the manual says to heat the car up beforehand is to make sure the thermowax/AWS is not getting in your way and holding the throttle partly open (which would give you a high reading on your fully closed measurement).

 

ohh good point... sorry i took that crap off both my FDs... :-) forgot about that stuff.

 

okay thank you for clearing that up for me guys.

 

Just thought some of you might want to see what actually goes wrong with these things:

 

The construction is actually pretty good, but instead of sealing it Mazda made it "breatheable". This, combined with the lack of any drain hole at the bottom made for a very bad idea in humid climates (like Houston). And yes, those are beads of condensation on top of the circuit board in the above pic.

 

Here's a better shot of the condensation:

 

So anyways, I figured I'd take mine apart just to see what was inside, but after cleaning all the buildup off the circuit boards and re-soldering(sp?) the connections, mine has gone from completely out of spec to working perfectly. So now I'm thinking of reusing it. Of course, I've dremelled the casing up quite a bit, but it's probably re-assemble-able. I'll post pics of the re-assembly in case someone actually wants to rebuild their sensor. FWIW, I could have done it with two cuts if I had known what was inside.

Oh, and as to why someone would want to go through the trouble? Dissection to re-assembly took me about half-an-hour, not having any idea what I was doing. Purchasing a new TPS? $198.

 

Re-assembled with hot glue. Probably not a good idea. I will most likely remove the hot glue on the outside and re-incase the whole thing in high temperature epoxy. On the other hand, it's in and my car is running.
Readings before:
VTA1: 0.83V-2.37V
VTA2: 1.29V-3.92V

Readings now:
VTA1: 0.50V - 4.37V
VTA2: 1.00V - 4.97V

 

good data :-)

 

Does anyone know whether "gcthree" found his gremlin? I'm in exactly the same position with car down, have done the same diagnostics...

 

well i get the perfect volt readings almost at extreme clock wise position. but there the car does nt run good i test drove and adjusted it where i liked it some in the midle position car runs great but voltage there is 1.76 closed and 0.86 closed for the black wire. strange isnt it but car runs here good and on the corect setings with the metter it runs pretty bad with lots of hunting dor idle

 

If you have a powerfc, you need to have it re-learn the correct settings for the idle air control valve after you fix your tps setting.

 

BTW, I also had to tighten my throttle cable before I could get my PFC to read 5V at WOT, i.e. even with the pedal all the way down I wasn't getting WOT before.

Now I am.

The car is scary fast.