I am having major issues in relation to the idle speed when my 1996 Ford Escort 1.8 16V Si is in motion.
Whilst in a stationary position, the idle speed is in the correct position of about 750 rpm. When you are driving the vehicle and put the clutch down to change gear the rev counter needle should drop to the 750 rpm mark. However this isn’t the case and the needle is only dropping to about 1100 rpm.
If you keep the clutch down or take the car out of gear and coast, the needle remains in the 1100 rpm position. As soon as the car comes to a complete standstill and remains in the stationary position, the needle drops to the 750 rpm position.
The position of the needle when the vehicle is in motion occasionally drops to about 900 rpm and sometimes only drops down to about 1300 rpm.
I replaced the spark plugs, idle air control vale, throttle position sensor and mass air flow sensor but none of these altered the fault.
The vehicle was then tested for fault codes and the garage changed the HEGO switch crankcase, charged £175.00.
This didn’t correct the fault at all and the vehicle was inspected by Ford.
The only fault code given should that the complete HEGO switch was faulty, this was replaced and I was billed £205.00.
I took the car for a road test to discover that the fault still existed and one of the Ford technicians came along to see what I was talking about.
He then tried to fob me off with the fact that this was a normal function of the car and that the rpm will be high whilst the wheels are in motion and will only drop to 750 rpm when stationary.
It didn’t do this before and has only been doing so for two months and none of the other cars I drive do it.
The two garages will not accept that they don’t know what the fault is and I am stuck with it.
Can you help? What could the fault be if there are no codes showing following tests by Ford and the other garage?

how about something as simply as cleaning of the intake either by spray or by actually taking it off the car? Just because ford looked at it dont mean anything I personally have a bad taste for FORD techs right now for my car was looked at (was told nothings wrong) and the very next morning I had the same exact problem. When I called them the next day they told me they'd recheck the car but I'd have to repay the 89.00 to have them look at it.

I have previously removed the intake to check for blockages and it is totally clear so no obstructions, there isn't anything preventing air from flowing into the air filter section.
I originally thought that it must be something to do with the airflow as the fault only occurs whilst the vehicle is moving.
Thanks for your thought anyway.

1.8 dohc high idle can be idle validation switch sticking. it's located at the throttle stop on the throttle body.can you lube it?