Slow throttle return when rolling along.

[J44EAG]

OK. All is still not lost, Duncan.

If you take off the air induction trunking to the throttle body, you will find there is the throttle plate sitting inside the throttle body. The plate angle varies in the same way as the butterfly plate in a carburetor when the throttle pedal is pushed. The difference between a carb and this electronic throttle body is that a stepper motor controls opening and closing via the Power Train Control module (ECU). You may well find both the throttle plate and the throat caked in black crank case breather sludge. Choking can get so bad that little or no air can slip around the plate and throat and idle gets compromised.

If that is the case, then don a pair of inspection gloves, some lint free rag and a spray can of carb cleaner, switch cleaner or some acetone. Carefully remove all the gunge on the plate and the throttle throat. Throttle body cleaning though is often best done by removing the throttle body from the car. Before you begin, obtain a new gasket from a dealer. Go very easy on the throat. It is covered in a coating which can easily be worn away. So use plenty of cleaner to soften any grunge up. It can be a filthy job so have plenty of clean lint free rags to hand.

Restoring the air gap between the throttle plate and throat can work wonders. Sludged up, the car can be a very poor performer.

See how you get on with that.

Mike K

[duncanwoolgar]

Thanks Mike for your last post and my apologies for only just replying. I have only just noticed your reply as I have logged on to post my next part to this saga.
The inside of my throttle body and indeed the whole inlet manifold is very clean as I took the whole lot off when changing plugs gaskets breather hoses etc etc. I have even completley stripped a spare throttle body to pieces to understand how they work. It has been an educational and interesting exercise, inside they are very well made with metal gearing from the motor to the butterfly plate.
Last night I changed the big rubber air ducting that goes from the filter box to the inlet manifold complete with air temperature sensor. This seems to have done the job and the car is now a joy to drive, hopefully it will stay that way. Tonight I will inspect the old one very closely to see if it had any holes or cracks in it but I suspect the problem was due to the air temperature sensor which does seem plausable.
Fantastically happy Duncan

[duncanwoolgar]

For anyone who is interested, upoun researching this problem I discovered that there is no stand alone idle valve on these cars. The idle control is all done by the electronically controlled throttle.
A big thanks to everybody who has contributed to this thread with ideas and advice.
Cheers Duncan