Throttle pot?

[jned2]

My S3 starts fine and accelerates hard with no issues, it's the bit in between is the problem. If I gently accelerate the engine misses or "coughs" and kangaroos for a split second and then goes. Trawling through a few earlier posts similar problems seem to have been caused by a problem throttle potentiometer or position sensor,I'm presuming they're the same? A few questions a) Do you think my diagnosis correct? b) I've read it can be solved by "unplugging"? c) Where is it, I don't find the picture in the bible particularly useful? Thanks in advance.

[GreenV8S]

Might well be that, although there are plenty of other potential causes of those symptoms. You can test the pot by connecting an analog resistance meter between the wiper and an end terminal and looking for the resistance to vary smoothly as you move the throttle. It might also be a wiring fault in the throttle pot circuit, or various other faults causing the engine to run out of tune under those particular conditions. It could even be a fault in the distributor, or the vacuum advance plumbing to it.

[MisterTee]

The throttle pot is located towards the front of the plenum chamber (drivers side) just underneath the idle speed control valve.

Hopefully this pic might help - the picture is taken from the front of the car facing the engine with the air pipes removed

http://www.andrewc.org.uk/tvrgit/IMG_8855.jpg

In this picture it is arrow number 5

Andy

[blues3]

Some info here...

http://tvrs3.net/Car%20Pages/Engine/The%20TPS%20(T...

[glenrobbo]

I had a throttle position sensor or TPS ( same thing as throttle potentiometer or 'pot' for short ) fault on my S3C on the Eurotour. Idle speed suddenly increased to 2400rpm, a bit of a problem in heavy stop/start start traffic on a hot and very wet day! Disconnecting & reconnecting made no difference. The sensor is a sealed unit with a nylon D-shaped driven socket that fits on the throttle spindle which drives the 'wiper', presumably a rheostat type of variable resistor or a magnetic reluctor and with a two pin connector for the output wiring to the ecu.
Thankfully RayTVR had a couple of brand new spares, swapping out the old for new only took a couple of minutes, two screws and the engine then idled perfectly.
Obviously there a few possible failure modes for the TPS, because the signal to the ecu then causes incorrect air/fuel metering.

Thanks Ray for your generosity, I shall make a further contribution to this year's chosen S-Club charity, MacMillan Cancer Support as you suggested. However it will be after my return from a family holiday.

[jned2]

Thanks for all the replies. I've just disconnected the lead from the throttle pot and gone for a short spin, it seems to have sorted the problem. Two questions a) is it ok to drive far with it disconnected? b)on an S3 is it ford part no.6854780? Thanks again.

[mk1fan]

Opportune timing this thread

[BillC99]

I bought one from LSM off ebay. works fine

[jned2]

BillC99 said:

I bought one from LSM off ebay. works fine

Thanks, was it part number Ford 6854780 / intermotor 19935 by any chance? Still wondering if I can run the car for any length of time with the sensor disconnected, anyone help?

[RayTVR]

My understanding is that without the Throttle pot connected the ECU will go into 'limp home' mode so will start and run, but probably will be well down on power. Without the TPS connected it wont have a signal to set the correct fuelling so will presumably under or over fuel, so probably not a good thing for long runs..

[RayTVR]

This is the one I have fitted also from LSM

clicky

[jned2]

Thanks again to everyone, I've ordered one from LSM.