My wife has a 1.4 Focus Mk1.

She mentioned the other day that it was 'ticking over funny'. Sure enough, when it's warm it ticks over about 1200rpm and a bit erratically. I suspected the MAF so unplugged it, but it made no difference whatsoever, the car seems to drive exactly the same. Whenever I've unplugged the MAF on any car previously for diagnostic purposes it's been really noticeable.

I'm therefore guessing it's the MAF and the car is reverting to a cold start map (?). Before I fork out on a MAF has anyone else got any other suggestions?

I can't see that it's just developed an air leak, and there are no fault codes.

 

It could be a faulty lambda too. But then again surely you would have fault codes stored.

 

Vehicle speed sensor I predict. Revs jumping between 800 and 1200?

 

In between sparkplugs 2/3 there is a wire going down through a gromet, usually covered in a brown protective coating. Ontop of the head there is a head temp sensor. More than likley at fault
You can see the sensor in the picture below to the left of sparkplug number 3.

 

I replaced the VSS about a year ago (what a twat of a job that was)

Would the head temp sensor not flag up a fault code?

 

Shouldn't do, just make the engine think it was cold.
I'm not quite sure if it controls the temp gauge though.

 

Temp gauge, and everything else is 'normal'. Just seems odd that unplugging the MAF made no difference.

 

Could be the temp sensor, my last one was fucked, got no fault code. Also, lambda might not throw up a code either, my old one was also faulty and it didn't. Although I think it was due to being covered in shite, as the car was burning more oil than petrol. (brilliant car I bought )

 

Does it run @ fast idle when you're driving? Or is it running @ fast idle when stationary?

If when moving try disconnecting VSS and try it.

If when stationary, wondering if ISCV is sticking , not returning to fully closed position (give it a clean)

Lambda wouldn't make it run fast.

CHT sensor 'could do' but I would expect a DTC and having worked on Focus pretty much all the time it's been in production I have never replaced a CHT sensor on a Zetec for being faulty. (first time for everything tho,eh) I would get it data-logged on IDS to check though.

Check the PCV piping and stuff under the inlet, have had them suck flat and cause running issues.

Worth spraying round the inlet with WD40/whatever to check for air leaks .

Oh, worth having a look in the throttle body to see if it's gunked up as well.

 

if its doing funny things and not putting up any fault codes... and you have already ruled out the MAF
then i'd say, as GVK says above, Idle control valve.. (if its 'sticky' it will be working, just slower than it should, hence the wandering of revs)

these were terrible on the first Zetecs, but not sure how much better they were on the black tops in focus'..

 

IACV would be my first port of call..

Ginge

 

Thanks for that, plenty to go off. It's only when stationary, so the ISCV does look like the prime candidate. Especially as it's behaving normally in every other respect - not using any more fuel, no hesitation or flat spots, no loss of performance.

Will whip it off over Christmas and give it a good clean.

 

common for split breather pipes from pcv valve

 

My money would be on these too

(i've replaced a few sets)

 

Same problem when I originally had the black top 1.4 in my first Focus, turned out to be the ISCV. Then threw shit load of nitrous through it

 

Took the ISCV off, and it was disappointingly clean inside. I gave it a good blast with carb cleaner just in case, but it's not made any difference.

It's a 70K car that never been messed with, so if the ISCV is anything to go by I doubt the inlet will be gunked up.

Went for a drive to warm it up and it's odd as it drives perfectly, but when you stop the revs 'hang' at just under 1500rpm for about 3 seconds before dropping down to just under 1000 (still feels 100rpm or so too many). It's more annoying than anything else.

Does that still sound like it could be PCV related before I get it up in the air?

 

what about the TPS?

 

Wouldn't the TPS flag up a fault code?

 

its suposed to.
I have had various faulty sensors in the past that haven't shown up on certain fault code readers.
what code reader afre you using?

 

Disconnect the VSS and try it, and make sure the clutch pedal switch works.

 

has the car got a throttle cable? if it has are you sure its not sticking or fraid anywhere?

 

Found it! There's a thin rubber vac pipe that goes from one side of the front of the block under the inlet manifold to the other side of the front of the block, and tees off vertically to a small cylindrical sensor thing. There's a 2in split in it!!

 

i was gonna say a vac leak! lol

lad at work has a 2.0l 306 cab and that was revving all over the place. tried 2x iscvs on it, as the first one he got was wrong lol.
that made no difference and was a bit of a head scratcher.

we rear somewhere on the net to unplug the batt for 30 seconds, its been fine since on the original iscv!

cars do odd things somethings...!

at least you found it tho!

 

Taped up the split temporarily - and the issue's gone... although it does seem to want to stall instead now I'm hoping the ECU just needs to get used to it!

 

Damm it, was going to mention that pipe. Mine was split to hell and had no symptoms other than a loud intake!

 

if you have the radio code, disconnect the batt for a minute

 

That's exactly where this one was split! Does the whole section come from Ford? Or do you have to order the hoses individually? It's a bit of a pig to get back on because of the manifold!

 

I won't lie, pig of a job! Easy, but an absolute pig without removing the inlet.

Part number from ford is FMU 1337254 and I paid Ł12.15 for it.
The hope just pulls off, I removed the idle speed control valve (and if you have it) the wiring going to the MAP sensor.

A little bit of oil on each end of the hose to push it on and some patients. Will go on eventually.

This is a picture I took showing everything I removed

Think I've named it all.

Have fun

 

Nice one Dan, glad you have found the problem

 

Nice. Thanks for that. The pipes are quite perished so it only took about 10mins of fiddling to get the old ones off, taped up, and on again, but I suspect that new pipes will be a bit trickier!

 

Dan, drop me a pm if you need radio code with your M number off the set.

If not see if there's a 3 amp fuse in the fuse box (poss under bonnet) this for KAM

Keep-alive-memory - pull the fuse out for a minute or two, re-fit and let car idle for a couple of minutes to re-learn the idle values.

 

It's got an aftermarket stereo, but thanks all the same. Will have a look for the KAM fuse tomorrow when it's light!

 

the same issue plagues the dohc sierra's, but it's a metal pipe that runs behind the head for the crank case breather

 

The 1.4 doesn't have a MAF sensor. So I don't know what you unplugged initally in your OP. That PCV hose is usually the culprit and in this case. Glad you sorted it. Happy Christmas .

 

Some do, some dont! It's usually luck of the draw.
You either have a MAF or a MAP.

 

Oh ok! I did wonder why it made no difference to the car when I unplugged it. I wasn't 100% it was the MAF, but after googling I got the impression they did have one. It must have been a MAP sensor I unplugged - the one at the engine end of the inlet hose.

Either way, I found the fault. Just as well I didn't try and order a new MAF!!!

 

Some have them according to this...

http://www.ebay.co.uk/itm/190492009039?redirect=mobile

Much oddness!

 

As said, some do but some don't and have a TMAP on the intake, the MAF is next to the airbox if fitted. Guess it when they changed to the turn signals in the headlamp whenever that was.

 

If you disconect the MAP sensor the car will hunt for idle.
Also the engine has a little feature where it holds the revs for a split second while you change gears to make it smoother. Disconect the map sensor and you loose this feature, you WILL notice it. You will be kangarooing everywhere if you have gotten used to it too

 

At least you found it.