Good Evening.  

I have a Mk2 2005 1.6 Petrol Ghia Estate Auto.

Recently the car is idling unevenly and once warm the revs drop off nearly stalling before recovering.  This happens cyclically every 5 seconds or so in neutral or park.  If I turn the engine off and restart it starts okay and then cuts out unless I maintain some revs, or put on the aircon, which I assume tells the ECU to up the revs as extra load is being put on the alternator.

I have had new plugs and filters put on since it started with no change.  I was thinking MAF sensor but for the life of me cannot find one on the car.

I have changed the MAP sensor too with no effect.

1) Anyone have any ideas what’s causing it.

2) Should I have a MAF sensor and if so where is it?  

When looking online the location of other Focus MAF sensors is obvious and description of faulty one seems to fit.

Any help would be gratefully received

Thanks in advance. 

 

 

Further to my last.  When I stick my reg through numerous online spares shops it gives a replacement MAF sensor OEM part number of 3L3A-12B579-BA.    The question is, where is this located??

The MAF, if you have one, will be located on the air intake tube, between the air filter box and the throttle body. However instead of a MAF you may perhaps have a MAP/TMAP like mine which might be why you're having trouble locating it. My TMAP is located on the throttle body. Part-matching systems aren't always accurate.

Sounds to me like you have a vacuum leak, I believe there is a pipe under the back of the inlet manifold, that splits, allowing non metered air, might be worth getting a smoke test done. 

7 hours ago, rd457 said:

The MAF, if you have one, will be located on the air intake tube, between the air filter box and the throttle body. However instead of a MAF you may perhaps have a MAP/TMAP like mine which might be why you're having trouble locating it. My TMAP is located on the throttle body. Part-matching systems aren't always accurate.

Hi.  Thanks for you reply.  I have replaced the MAP sensor which has had no effect.  Forgive my ignorance is a TMAP the same as a MAP, I wouldn’t have both? 

4 hours ago, sttwoton said:

Sounds to me like you have a vacuum leak, I believe there is a pipe under the back of the inlet manifold, that splits, allowing non metered air, might be worth getting a smoke test done. 

Do you mean this pipe?  Found a split on the back of it where it kinks round.  👍

16 hours ago, rd457 said:

The MAF, if you have one, will be located on the air intake tube, between the air filter box and the throttle body. However instead of a MAF you may perhaps have a MAP/TMAP like mine which might be why you're having trouble locating it. My TMAP is located on the throttle body. Part-matching systems aren't always accurate.

Hi.  Thanks for you reply.  I have replaced the MAP sensor which has had no effect.  Forgive my ignorance is a TMAP the same as a MAP, I wouldn’t have both? 

MAF = Mass Air Flow

MAP = Manifold Absolute Pressure

TMAP = Temperature and Manifold Absolute Pressure (just a combined temperature and MAP sensor)

You'd only have one of these three.

35 minutes ago, rd457 said:

MAF = Mass Air Flow

MAP = Manifold Absolute Pressure

TMAP = Temperature and Manifold Absolute Pressure (just a combined temperature and MAP sensor)

You'd only have one of these three.

Many thanks.  It will be the MAP then.  

So the crankcase breather hose as suggested was spilt. Changed it and 🤞 it does the trick.  It is certainly idling more evenly.  Revs weren’t dropping off.

Only place I could get the part today was from Ford’s themselves.  Chap in there said that it was a common replacement part a few years ago.   

Thanks for all your help.  

Yeah it’s pretty common on the petrol four pots found in that era of cars, especially on the 1.8 and 2.0, although on them engines, it makes the idle higher.