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Gallagher99
Gallagher99, Senior Vehicle Technician
Category: Ford
Satisfied Customers: 3206
Experience:  SVQ LEVEL 3, QAULIFIED FORD SENIOR TECHNICIAN , ATA REGISTERD ,12 YEARS EXPERIENCE
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engine runs erratically when in neutral, revs go up and down

Customer Question

engine runs erratically when in neutral, revs go up and down on their own,AA and garage agree that air getting into carburettor , cant find any leak?
Submitted: 2 years ago.
Category: Ford
Expert:  Gallagher99 replied 2 years ago.
Hi there ,good afternoon to you
Ok is the the last of the old shape mk3 Mondeo
Is this a 1.8or 2.0 petrol Varient
If you Rev the engine hard from stationary does it take a while to come back to idle /rest
Regards Brian
Customer: replied 2 years ago.

1.8

when it first happen the car cut out battery light on,had to accelerate to keep engine going,if you rev the engine while stationary the revs come back to idle, then will continue to

rev up then down on its own,on the aa report it stated that the mixture was entering to rich

Expert:  Gallagher99 replied 2 years ago.
Hi there thanks
Ok your fault lies with a split /collapsed L shaped breather hose between the PCV (positive crankcase ventilation ) valve and the inlet manifold
These were probe for splitting and causing infected air to be drawn into the engine thus causing hunting idle and slow return to idle
You can sometimes hear the hissing noise from the lower area of the inlet manifold this is the manifold sucking in the undetected air
To resolve the issue you need to replace this L shaped hose which is located behind the inlet manifold
The inlet manifold needs to be removed to replace this hose
The mixture will be too lean due to the air leak being undetected
If you need anymore help or advice on this issue please let me know
If you are Completely satisfied with my answer /advice
PLEASE RATE MY ANSWER
Kind regards ***** ***** and have a nice day
Brian
Gallagher99 and other Ford Specialists are ready to help you
Customer: replied 2 years ago.

thks one of the area garage is looking

Expert:  Gallagher99 replied 2 years ago.
Hi there no worries
If you need If you need anymore help or advice on this issue please let me know
If you are Completely satisfied with my answer /advice
PLEASE RATE MY ANSWER
Kind regards ***** ***** and have a nice day
Brian
Customer: replied 2 years ago.

brian re ford mondeo

the manifold has been removed and the hose checked ok, any

other idea,s to the cause of the erratic running of the engine

Expert:  Gallagher99 replied 2 years ago.
Hi there sorry for the delay
Ok if this L shaped hose is ok then check there isn't blanking plug missing as some of these manifolds have small rubber bungs covering ports used on earlier vehicles
From your description it definitely sounds as if the engine is drawing air thsst is undetected by the mass air flow sensor
Also closely inspect the manifold for any signs of splitting at the plastic welds of the manifd as these can swell open causing air ingress
Regards ***** *****
Brian
Customer: replied 2 years ago.

thks be back in touch

Expert:  Gallagher99 replied 2 years ago.
No worries
Regards Brian

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