Mk4 Fiesta 1.3 revs when starting

[andyj941]

Hi the wife has a W-reg 1.3 Fiesta which over the last few months has developed a rather irritating starting problem. Quite often it will rev when the engine is started up and then down, sometimes then stalling unless the ignition key is kept turned. It cycles up and down up to five or six times before it either stalls or recovers.

I have in the last 6 months changed the idle air control valve for a cheapo ebay one. In the last few weeks to try to fix the problem I have also changed the air, pollen and fuel filters, the spark plugs, ht leads and coil pack to no avail.

Is it possible the IACV I put on is actually causing this? Can I tell without sticking another one on? Anyone know what the problem is?

Thanks

 

[Mursal]

I'd look for air getting into the manifold after the air volume control, or failed coolant temperature sensor?

Had you considered getting the fault codes read by your local garage?

 

[greasedmonkey]

Cheapy air control valves from eBay are more trouble than they are worth. Same for air flow meters, MAP sensors and throttle position sensors. Get a decent one from a motor factors, or even a second hand one from a scrappy if funds are tight.

If you know anyone with an ultrasonic cleaner, you could try cleaning the original air control valve, but at best this will only postpone the inevitable.

 

[Belle427]

Id start by cleaning the throttle body as it could be sending a dodgy signal to the ecu via the throttle position sensor, this can have an effect on the icv position.

 

[andyj941]

Hi thanks for the replies. I cleaned the throttle body and the IACV with carb cleaner but no difference. I did however replace the throttle position sensor with a new one from a motor factors and there is a big improvement - the car now does one long powerful rev when it starts up rather than one after another. Going to replace the pipes as well to see if that makes a difference and will let you know how it goes.

 

[feynman]

Hi thanks for the replies. I cleaned the throttle body and the IACV with carb cleaner but no difference. I did however replace the throttle position sensor with a new one from a motor factors and there is a big improvement - the car now does one long powerful rev when it starts up rather than one after another. Going to replace the pipes as well to see if that makes a difference and will let you know how it goes.

This does have an airleak "feel" to it, but by the sound of the symptoms, it could be the multiconnector into the throttle position sensor.

Something well worth trying is to disconnect and clean all the multi connectors involved with the engine.

With the car and engine switched off, use a switch cleaner spray and then disconnect, spray into, and reconnect each multi connector 5 times or so to clean the contacts. Do each one in turn before moving on to the next so you don't leave one unconnected. Some might be a bit inaccessible, but you might be lucky and find a duff/dirty connection somewhere.

I don't know about Fords, but the connectors might have plastic catches to stop them coming undone. These can be fiddly to release, so be careful you don't break them.