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MG MGF Technical - How to test Throttle Position Sensor?

My 1996 VVC has high idle revs ~1500rpm

Also there is no engine braking whilst driving - when I remove foot from accelerator the revs remain constant (no-I haven't got cruise control).

It's not the throttle cable sticking - tiny amount of slack when idling.

I've also sprayed the innards of the TB and the butterfly valve with carb cleaner.

I've looked thru the archives and THINK it could be the Throttle Position Sensor. HOW DO I TEST IT?
When I disconnect TPS whilst the engine is running the revs increase.

Any other possible causes to my dilema?

Mike Coward
Michael Coward

Queue Dieter :-)

I suspect you will need a mutimeter to test the TPS, Dieter has some readings IIRC that you may be able to use as a benchmark.

Good luck

Scarlet Fever

> >Any other possible causes to my dilema?

This can be caused by the temperature cooling sensor. Try cleaning the contacts, as apparently this can be as good a cure as a replacement part, although that will set you back not much more than a tenner.

There's more in the archives and on (ignore the stuff about overheating, just look at cleaning the contacts and potentially replacing the part.)

Rob also has info on his site about the TPS - see

Mike - have you tried re-setting the MEMS/TPS?

To do this, turn ignition to position II, and floor the throttle 5 times within 10 seconds, and kill the ignition. Then restart the engine.

The TPS has a resistance range (see Dieter's web page - which you can use to interogate the TPS with a multimeter, but problems can also occur with the plug and wiring harness (see Paul Nothard's experiences).

However, the commonest cause of this problem is distortion of the plastic throttle body - particularly where cheap jubilee clips have been used to retain the filter in place (clamping forces are notoriously uneven).

Best option under these circumstances is to go for an alloy replacement (readily available from a number of sources).

let us know how you get on Mike :o)
Rob Bell

My money is with Dave, get some contact cleaner from Maplin or alike.

Incidently Rob do you have a spare temp sendor, I apper to have cooked mine with a welder.
Will Munns

If you are after a GTR206, then as it happens, yes I do... :o)
Rob Bell

Isn't that a Peugeot Rob?


Scarlet Fever

Erm, the brown one ( I have a spare black one if anyone else has a need)
Will Munns

Now now, don't swear on a public forum Andy! ;o) ;o) ;o)

Will - yup, that's the brown one! Drop me a mail with your mailing details. Did you get much further over the weekend? Okay okay, I'll stop bugging you and wait for the next exciting instalment of "project 16"... :o)
Rob Bell

Had to go to the worst wedding using wedding cars tunbridge wells in history, so did get a little done on Sunday, things have been going slowly since I went back to work!

It may breath tonight though!
Will Munns

Sent to your hotmail account
Will Munns

Got it Will. I shall sort one out for you this evening. :o)
Rob Bell


got it and replied to Mike's email.
Apology for the *under construction* site ;)
Though I think the easiest way to measure the function of the TPS is connecting a voltage meter with range 10 V to the middle contact of the TPS and to ground.
- ignition on
- turn throttle butterfly *by hand*
- see the reading between 0 ... 5V.

Yellow-Pink is Ve+
Pink-Blue wire feeds to the power supply ground.
Yellow-Green is the wire which leads the output (0...5V) to the ECU (Should be possible to be located at the ECU connector as well)

However, the inlet air temp or coolant temp sensor could cause similar trouble (IMO)

Dieter K.

This thread was discussed on 01/09/2003

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