cherrybeard Posted August 27, 2007 Share Posted August 27, 2007 Hi there, been testing the tps using a multimeter and think i have found a problem. I used the middle and one of the end pins to obtain readings. The resistance starts at about 570 (setting on 2000ohms) and from rest to halfway it sweeps up to about a 1900 reading before dropping to a zero (defaulted) value and making no reading whatsoever from halfway till the end. Does this co-incide with the problem im having whereby it feels like it doesnt make a difference if you push the accelarator past further than halfwayish? Or is this normal behaviour. Still cant tell whether im testing it right although me and my girlfriend both observed this trend in the reading. As you return the sensor from fully on, it doesnt pick up a reading until halfway down (about the 1900 mark again) and then falls as normal to about 570. Link to comment Share on other sites More sharing options...
Stu Posted August 27, 2007 Share Posted August 27, 2007 Yes it's fucked. You should get a linear sweep throughout the mechanical operating range of the sensor. Link to comment Share on other sites More sharing options...
cherrybeard Posted August 27, 2007 Author Share Posted August 27, 2007 Yes it's fucked. You should get a linear sweep throughout the mechanical operating range of the sensor. excellent, never have i been so happy to hear that something is 'fucked'. Means that replacing it will definately make an improvement to the running and wont be a waste of money, so long as nothing else is fudged. Best place to get one? Ford, motor factors? Could get one from scrappy i suppose now that i know how to test em first. in this case, do you know what the proper parameters should be? Link to comment Share on other sites More sharing options...
Stu Posted August 27, 2007 Share Posted August 27, 2007 I only recommend buying new, genuine Ford parts. Link to comment Share on other sites More sharing options...
cherrybeard Posted August 27, 2007 Author Share Posted August 27, 2007 Ok mate cheers stu. Done a few more test on all combinations of pins and have presented them below if anyone is interested. The pins are labelled A, B and C. If you cant see these numbers then you lay the tps flat with the spindle facing upwards and the pins towards you. From left to right is A - C. First test was done on the 20k ohm setting.Pins A and C Reading was 4.11 no change in reading throughout the sweep.Pins A and B 0.55 at rest to 3.96 fully wound.Pins B and C 3.78 at rest to 0.28 fully wound. This time the meter managed to obtain readings right till the end of the sweep although the last 30-40% of the sweep showed the same reading. Second test was done on the 200k ohm setting.Pins A and C Reading was 4.3 no change whatever the setting on the tps.Pins A and B 0.5 - 4.1Pins B and C 3.8 - 0.02 Similar set of results as well as the last 30-40% of the sweep not changing the reading at all although the graduant did seem smooth up until this point, maybe a little hesitant right at the start. Would be interesting to see if anyone else can perform the test and report back. Does anyone know how i would go about finding out what the proper values should be for each test? Apart from testing a brand new one which, knowing my luck, would be faulty. Link to comment Share on other sites More sharing options...
Stu Posted August 27, 2007 Share Posted August 27, 2007 You have to appreciate that TPS is just a potentiometer. The two outer pins join to each end of the track (and as you found will be a fixed value).. and the middle pin is the arm which sweeps across this track (carbon/resistive track).. In the car one end of the track is connected to 5v, the other to ground, and the wiper output will vary from say 0-5v (not quite, more like 0.25-4.75v). Link to comment Share on other sites More sharing options...
cherrybeard Posted August 27, 2007 Author Share Posted August 27, 2007 You have to appreciate that TPS is just a potentiometer. The two outer pins join to each end of the track (and as you found will be a fixed value).. and the middle pin is the arm which sweeps across this track (carbon/resistive track).. In the car one end of the track is connected to 5v, the other to ground, and the wiper output will vary from say 0-5v (not quite, more like 0.25-4.75v). very helpful, thankyou.Do you mean that it is a variable resistor? That would explain why the scale is reversed when using each end and the middle. Although not sure why one of the scales is offset slightly. How comes i have 'lost' the last part of the sweep? I take it i can only measure the output voltage once it is connected to the tb again. Can i do the test with the key in ignition mode and engine off, dont want to be pissing off the neighbours. Its not like the sliding contact gave way to wear and tear since it is at the throttle fully open and 3/4 open section. Unless the previous owner only drove foot flat to the floor and nothing else! Link to comment Share on other sites More sharing options...
Stu Posted August 27, 2007 Share Posted August 27, 2007 Just ignition on is fine, that supplies power to all the sensors. Link to comment Share on other sites More sharing options...
rstyrone Posted August 27, 2007 Share Posted August 27, 2007 I was just about to put up a post about the same thing.I foun this on a website that tells you the volts and how to test;http://www1.autozone.com/servlet/UiBroker?...23d8011f08f.jspThis is for engines up to 1990, Mines is 92 but think it should be the same. I went out and tested the wires, they were reading 5 volts, which was fine, but when i tested the wires while accelerating through the revs the volts dident move, i take it the tps is fooked? Link to comment Share on other sites More sharing options...
Stu Posted August 27, 2007 Share Posted August 27, 2007 One of the wires will always read 5 volts.... (with the ignition on/car running). Link to comment Share on other sites More sharing options...
rstyrone Posted August 28, 2007 Share Posted August 28, 2007 What about the volts not doing anything when i rev up? Am i doing it right Or will the tps be knakered? Link to comment Share on other sites More sharing options...
Stu Posted August 28, 2007 Share Posted August 28, 2007 As I said, one of the pins will always read 5v. One will always read 0v (ground) and the remaining one will vary with throttle angle. Link to comment Share on other sites More sharing options...
rstyrone Posted August 28, 2007 Share Posted August 28, 2007 I know, what im saying is the throttle angle wire should should be at 0v when throttle is closed and 5v when it is opened? When i tested mine the volts dident change when i reved it. So is the sensor knaked? Link to comment Share on other sites More sharing options...
Stu Posted August 28, 2007 Share Posted August 28, 2007 Quite possibly... or you were testing it wrong. 0v and 5v are fail values actually, realistic travel is 0.25-4.75v Link to comment Share on other sites More sharing options...
rstyrone Posted August 28, 2007 Share Posted August 28, 2007 Was just out at car, when i tested it and built the revs up slowly ot max the voltage stayed the same, but when i pressed the throttle hard in quick sucsessions the volts were jumping up to 5-6v. Is this right? Link to comment Share on other sites More sharing options...
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