Throttle position sensor fault?

[FlatheadFordV8]

Hi Folks,

Facelift 1.9CDTI 150.

I've got a problem with a missfire / judder at part throttle. If you drive at part throttle at normal sorts of speeds, there is an occasional missfire or momentary loss of power, sometimes when you just go to move the accelerator pedal slightly. If you drive hard, there are no apparent problems.

I did about 300 miles yesterday and tried different things to pin it down. It appears that it does not do it when the cruise control is engaged, and I am not pressing the accelerator pedal, so suspect it is the TPS that has a worn bit on the track.

I could change speed OK on the Cruise control buttons, and on the M62 the car was changing power for the hills etc and there were no problems.

Is it possible to clean the sensor or is it impossible to open up.

No lights come on and there are no faults stored, so I think the ECU thinks it is just me backing of the throttle rather than something being wrong.

[jamie1991]

I have this problem , every now and again i feel a slight judder / misfire like you say and again only when driving steady , ive ignored it so far but i would be interested to no what the issue is

[FlatheadFordV8]

Well I decided to have a look at the sensor and see if there was anything wrong.

I removed the sensor from the car. You have to remove quite a bit to get to it, so if this is the fault I will probably do a complete How2.

The sensor has a panel on the side with 5 screws. The panel can be rotated slightly to make some sort of adjustment to it. This is set at the factory, and the top right screw with the black paint on it sets it in place. If you mark the cover you will just be able to put it back as it was if you make sure the screw goes in exactly the same place.

tps2.jpg

When the screws are removed the panel just lifts off to reveal the carbon tracks and brushes. The rest of the assembly is just the pedal and spring mechanism so you do not have to touch that.

tps01.jpg

The photo shows that there was some carbon dust in there but what you cannot see is that the two centre tracks were quite worn with quite a significant dip in them towards the throttle closed end. It also seemed that the two brushes, which are made up of about a dozen tiny wires had a couple of the wires misaligned as if they had been digging into the track at some point and distorting.

tps3.jpg

I wiped the tracks with a clean cloth and tried to straighten up the tiny wires, but could not get them perfect.

Once the sensor was refitted, I went out for a drive, of 5 to 6 miles, and it did not judder at all.

Now I am not saying that it is cured, as I will drive it for a while to see if it has actually gone, but the sensor was not in pefect condition when I opened it up. I have just ordered a good secondhand sensor to try as well so I will keep you posted.

I have 100 mile trip to do tomorrow so that should be a good test.

[ThatAudioBloke]

Intriguing, mine has a pretty annoying misfire at very small throttle openings so the results of your test will determine if I open mine up or not!

[jamie1991]

I have just removed mine and opened it up it was really easy , there was nothing that really stood out to me such as a build up of dust etc it was clean , i wiped the tracks over anyway but i have a feeling my issue may be something else , out of interest how many miles has your car covered ?

[FlatheadFordV8]

It's done 135000. Time will tell if it was the problem, because as we all know intermitant problems are a pain to eliminate. When the secondhand one arrives I will open that one up before I fit it to see how it compares. Hopefully it will not have the worn tracks, as it is supposed to be a low milage unit, but then they all are when they are for sale arn't they!

[jamie1991]

It's done 135000. Time will tell if it was the problem, because as we all know intermitant problems are a pain to eliminate. When the secondhand one arrives I will open that one up before I fit it to see how it compares. Hopefully it will not have the worn tracks, as it is supposed to be a low milage unit, but then they all are when they are for sale arn't they!

Lol yes some peoples idea of low mileage are different to others but that was sort of what I was getting at, my car has covered 69000 and the sensor showed no real signs of wear so if it is a genuine love mileage unit it should be fine

[FlatheadFordV8]

Well I did the 100mls yesterday, and all was fine for the first 30mls, then it started to judder again. Initially it was just when you moved the pedal very slightly, and then it got worse and was doing it at random. I will report back when I have fitted the replacement sensor, as I know mine still has the fault with the little brushes.

[Tyler Durden]

Well I did the 100mls yesterday, and all was fine for the first 30mls, then it started to judder again. Initially it was just when you moved the pedal very slightly, and then it got worse and was doing it at random. I will report back when I have fitted the replacement sensor, as I know mine still has the fault with the little brushes.

Well?