Hello,

Just hoping someone has had the same and knows what I should be replacing to get an easy/cheap fix without going through everything trying to guess and eliminate unnecessary parts and wasting money at the moment.

The past couple of weeks my Focus has been revving up and down when waiting at traffic lights or junctions, it only does it once the engine is warm, seems as though it will stall but hasn't yet. It's not had a full service for about 18 months now with the oil and filter being changed about 14 months ago, it has roughly 45,000 miles on the clock. 

I've read issues about moisture getting to the plugs, leaks in hoses, problems with the PCV valve (there's a bit of oil in the air filter box, is this related?), faulty connector on the coil pack? There's no fault codes coming up. 

Anyone had the same problem and knows/thinks what it is most likely to be?

Thanks in advance, any input and help is welcome. 

Sounds like an ISCV (Idle Speed Control Valve) or MAF issue to me.

Unplug the MAF and see if it runs any better, if not then either clean or replace the ISCV.

On my mk1 it was the idle control valve take it of and clean through with carb cleaner in a spray can worked for me 

Thanks for your replies, I've not had much chance to have a look today but forgive me if I'm wrong but there's no MAF sensor on this model, I can't see anything obvious around the air filter box. Having read about that I found that some models have a MAP sensor instead, is that worth getting off to clean? 

I'm no professional but I've taken a couple of pictures (below). Am I right in thinking the connector with a red pullout clip is the MAP sensor? It looks tricky to get to, would the inlet manifold need to come off? Theres also another connector to the side of the EGR valve which I would assume is the throttle body sensor. Am I mixing one of those for the idle speed control valve as I didn't manage to see that so if someone could point me in the right direction to find it that would be great.

No pictures/videos online seem to be for the same engine as mine so difficult to find exactly what I'm looking for.

 

 

I forgot to mention that I tried the fault code reader again today and it gave a fault code for misfire in cylinder 4, I took all the plugs out and they seem fine, afterwards the fault code had gone but still idle problems I pulled off each ignition lead whilst running which caused an actual misfire so not sure what to make of that.

Is it the car in your profile? and not a different car?

The anti stall would cause the revs to rise, until you put your foot on the brake for a few seconds, but beyond that, it should not idle eratically, that would suggest you have a dirty sensor.