Do you want the Road Tax system to change? Do you have thoughts on the potential changes to the Road Tax system? | No thanks

What is causing my daughter's Ford Ka to over-rev when idling?

My daughter has a 2004 Ford Ka. It has developed an intermittent fault whereby it will often over-rev when idling or rev in "pulses" as if someone is fanning the throttle. It has now also started running off at lights/junctions etc. I have taken it to two local garages who hooked it up to a computer but could find nothing wrong. They also checked for air leaks and drew a blank there too. They both suggested I took it to a Ford main dealer. Would this be a sensible option for such an old car and are they likely to have any more success diagnosing the fault than an independent garage?

Asked on 16 March 2013 by SR, Farnham

Answered by Honest John
First, pour a can of engine fuel system cleaner into the petrol tank and fill up with Shell V-Power petrol. If dirt or hydrocarbon varnishes are causing the problem, that may help. No joy, then might be the mass airflow sensor, the throttle position sensor, or the idle control valve - all garage jobs.

Update: SR later wrote back to tell us this had worked.
Similar questions
My daughter has a 2004 Ford Ka. It has developed an intermittent fault whereby it will often over-rev when idling or rev in "pulses", as if someone is fanning the throttle. It has now also started running...
I have had problems with misfiring, loss of power, and red engine management lights coming on on two cars which where filled with unleaded petrol at a supermarket. One of the vehicles has needed to have...
I have just bought a 2008 Mazda MX-5 2.0 Sport RC from a franchised dealer, the car was serviced in April by the dealer and has 45,000 on the clock. After running it for a few days, and filling the tank...
Related models
Excellent drive. Strikes a fine balance between handling fun and ride comfort. Plenty of used ones around. Peanuts to run if you find a good one.
 

Ask Honest John Right column

Value my car