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Mondeo Engine Fault


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Hi Everyone,


I am after some advice on my Mondeo, (Not the kit car, I know, but thought I would put this past you very clever people).


If you own a Mondeo, (mk3), Then you are probably familiar with the splitting PCV pipe, just behind the inlet plenum.


Well, after replacing this on my Mondeo, I seem to have run into a very weird problem and presents itself like this:


When I start the car from cold, the idle is much higher than it used to be (Now about 1400-1500rpm) and drops to 1100 after a short period of warming up. Normal idle when warmed up would be 750rpm. If I leave the engine running or just drive off the revs will never drop to the norm, UNLESS I turn the engine off, wait a few seconds and then start it again.


However, it gets weirder....


When started from cold (apart from the idle being high) everything seems normal. Until it has warmed up! Then if I am in say 2nd gear (2000 rpm) and accelerate to change up into 3rd, (foot off the accelerator drop the clutch), the revs will now shoot up to 3000rpm and stay there until I engage the clutch again. If I accelerate hard the revs could go as high as 4000rpm!!.


Once again If I pull over turn off the engine wait 30 seconds, start her up, she's all back to normal between gear changes.


At first I thought air leak but this would be the same regardless of stopping and starting engine.

Engine Diagnostics show no faults and nor does using the elm327 analyser...


But I have now replaced all the following:


Throttle Position Sensor

Engine Coolant Sender

Manifold Absolute Pressure Sensor/temperature (all in one)

O2 Sensors Pre and Post Cat

PCV Valve


Clutch switches are working and so is EGR.


So I am left with the ECU, which seems to have a problem switching out of choke/reading mappings until its briefly reset.


But before I go down that route does anyone have any other ideas? (apart from scrapping it :))








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Can you read throttle pot values with the elm? I would check the values through the range and when you have the revving fault when changing gear. I don't know if the mk3 was throttle cable or fly by wire but it sounds like it's getting the wrong values or sticking.... you don't have to recalibrate the throttle pot settings when changing it perhaps?


I doubt the IACV as it regulates a small amount of air, I doubt it could supply enough air to get the engine to rev to 4000 on its own. Also the ecu would not be seeing throttle input so the mixture would be overlean and the engine would cut out.


As I said I would look at the throttle cable/ position sensor with the elm tool and look at the Max and min values...

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