2006 Mondeo help needed.

[Triple D]

My 2006 Mondeo 1.8 idles at about 1500rpm and randomly revs itself to about 3k revs before dropping back down.

A friend who is usually very good with cars admits even he is stumped. I googled it and found a list as long as my arm of things that "could" be wrong. These range from a buttetfly on the throttle to a pipe in the crank case.

I am not very mechanically minded so thought I would ask you guys before I go throw any money at it. I have asked the same thing I ford section but got no response

Thanks in advance. Cheers

[catman]

Idle control valve faulty.


Tim

[SV8Predator]

Throttle position sensor.

[Billy_rfc]

Plug in a fault code reader and it will hopefully point you in the right direction.

[ShaunTheSheep]

To get to 3k rpm, there's unmetered air getting in somehow. Surely it's tripping a check engine light if it gets as high as 3k rpm?

I said unmetered air - i got there because If it was something to do with spark, then it wouldn't be able to rev to 1500 just with a spark fault and correct air / fuel, no change to timing could promote that condition without an increase in air volume into the cylinders.

If it was something to do with fuel, there wouldn't be enough air to combust it, all that would happen is it'd judder and stumble due to running rich.

So it's excess air causing this, but how? You could use a scan tool to observe measured air mass & o2 while it's doing it but you said you're not that way inclined so you could try:

• Unplug MAF (google it - dead easy and safe to do), this will cause it to run open loop. You should see no difference with it plugged in or out, ruling out a faulty MAF
• Ideally get something combustable - i use carb cleaner spray but you could use a propane torch (unlit!!) if you have one. Assuming you don't, get a skooshy bottle with water and mist it over all the intake trunking between the MAF sensor up to and including the intake manifold. Work along slowly and methodically, don't drench it, just a medium mist all round it and listen for revs dropping off, you may be able to find a place where you can consistently squirt and it'll cause the idle sound to change, if so, bingo there's your leak, you might be able to hear it sucking if you put your ear near.
• If that doesn't find it, you could check anything that uses vacuum (such as the brake booster) by blocking off one ancilliary at a time and see if there's any change

[Pommygranite]

Has the gaffer tape on your bumper come loose? Put a bit more on and she'll be right.