Disconnecting TPS Sensor

[TouringMatt]

It works and is set correct so any reason why an engine should idle/rev better with it disconnected?

Cheers
Matt

[Morat]

which wire are you talking about? The one that runs from one of the HT leads to the diagnostic plug? If so, then mine did run better without that lead connected, although its having all sorts of problems right now

[TouringMatt]

Nope, its the one that comes off the sensor on the underside of the throttle body.

I'd love to understand what does what and how it all works, but i dont!

Cant understand why disconnecting the sensor makes the idle speed increase, which in turn makes throttle pick up better, in theory it should make things worse?

Wanted: stable idle and correct fuelling!

Ditto, mines terrible when cold

Matt

[TouringMatt]

Bollox to that theory, started but coughed like bitch this morning. Being under the bonnet at 5.30 in the am aint good!

Back to ze drawing board meine Freunde!

Matt

[Ant]

the TPS has three functions.

when the throttle is closed it tells the ECU that the engine is required to idle, so the AFM signal is ignored and the car fuels from its base map settings, these kick the ICV into life and should ensure the idle is smooth and stable @ 680 rpms, more if cold of course, injector duty is fixed @ this point unless the rpms change, thats why you can alter the idle CO% setting with the AFM bypass screw, it lets in more/less air as required.


When the throttle is wide open ( WOT) the TPS send a signal to the ECU again, this time telling it to use the WOT fuel and Ignition maps only, and again to ignore the AFM signal.

The AFM only "works" for the 70% of midrange and light load, all other settings are run from the TPS.


if the rpms are above the setpoint ( 1200rpms iirc ) and you shut the throttle from say 5K rpms, the TPS will tell the ECU to cut the fuel flow to the injectors until the setpoint is reached, this is fuel cut and aids in economy and engine braking too.

now you can see why a failed or badly setup TPS can cause lots of grief with running( hopefully ).


HTH

really should do a write up on this...

[TouringMatt]

Thanks for the reply Ant

when the throttle is closed it tells the ECU that the engine is required to idle, so the AFM signal is ignored and the car fuels from its base map settings, these kick the ICV into life and should ensure the idle is smooth and stable @ 680 rpms

if the rpms are above the setpoint ( 1200rpms iirc ) and you shut the throttle from say 5K rpms, the TPS will tell the ECU to cut the fuel flow to the injectors until the setpoint is reached, this is fuel cut and aids in economy and engine braking too.

From stone cold, if i kill the revs from say 5k, they drop rapidly and dip to about 500rpm, and rise/fall around 5-700rpm.
However once warm they drop quickly to around 1200rpm then to about 900rpm, nice steady idle

Does it sound to you like there is some suspect wiring in there? The ICV should control the idle but until everything has warmed up it doesnt. I have noticed in the past that disconnecting the ICV, regardless of engine temp, does nowt......

I have tried 2 other ICV's, all with the same result

In my hunt for problem elimination i have a spare TB that im going to try, AFAIK its never been tampered with.....

Cheers
Matt