Auto Choke ??

[M@H]

Has it got one.. and if so how does it work ??

..could it explain why my revs slowly rise then stick as 2200rpm when I start the car up..?? (and for the next many miles) but drop back down and start again when I switch off and re-start the car..

I've already been through the relays and fuses in the passenger footwell and found no problems.. the next thought is the throttle pot..

Cheers
Matt

[shpub]

There is a choke but not as we know it...

Choking is done by extending the fuel pulses to the injectors on the 2.9. On the 2.8's it is done by an extra injector thingy that comes on when cold that increases the mixture.

Steve

[M@H]

Cheers Steve... its the 2.9.. I'm stumped as to what's wrong with it... I think I'm gonna have to hand it over to the "experts" who can then lighten my wallet... ..unless you've got any good page numbers for me ..I've read all the sensor pages and can't find anything to match my problem...

Cheers
Matt

[johno]

If the car is idling up to 2200rpm when cold it could be all sorts of things. But I would look at .......

1 - Throttle Pot (always going wrong)

2 - Engine Temp Sensor. If it thinks its really cold it will over compensate.

3 - Dodgy earths causing false readings

4 - The small and peculiar 'S' gremlin that is making mine do a similar thing but not when the experts have it in their garage. Possible loom problem.

5 - Aux Air Valve is sticking open. Can check be connecting and disconnecting the power supply to it to see if you can hear it click. Or a sharp 'rap' with a screwdriver to hear whether it closes shut or not. Sometimes they stick open due to carbon build up....

Cheers

Mark

[M@H]

Cheers Mark...

...one thing on the Throttle pot... If my engines Idling (at whatever speed ie 1000 or 2200rpm) what happens if I disconnect the connector to the pot... or what should happen..?

I don't really want to go and get a new one without proving to myself that the existing one's Knackered..

Cheers,
Matt.

[johno]

If you disconnect the Pot the ECU then sits in 'limp home'.

This doesn't essentially tell you that the Pot is knackered but I find it is a good marker. Very good marker.

For example PaulV's engine started running rough at idle the other weekend and did not want to start when cold. So we disconnected the Pot and the can ran fine. Reconnect the Pot and its all over the show again.

Bought a new Pot and fitted that and the car is on song again. Proof of the pudding.

Beware though.... it is possible that this is masking another issue with the engine though. A fault code reader will tell you if the Pot is knackered, and the only way to accurately test a Pot is with an oscilloscope.

My engine has been running really rough and far too rich. First thoughts were Pot again !! So diconnected it and it didn't run properly without it.

Car is now at Tower after trying a couple of other things and they have tried all the sensors and checked the loom. The car is now running fine but they do not know what they have done to get it right !!! So they are trying to get it to run rough again to see if they can solve what it was that caused it.

Having had similar problems previously I have solved them myself, but this one is a bugger and I'm increasingly keen on handing it over to people with the Diag kit to be able to look into these things properly.

Cheers

Mark

[M@H]

Cheers again Mark, I'll have a fiddle when I get home.. perhaps I should try my local ford garage, see if they've got the relevant Diagnostics stuff...

See ya,
Matt