Mondeo revs up and down when coasting

[paul r w]

Hi,

I have a 2006 2.0L petrol Duratec HE, when I lift off the accelerator and coast the revs jump up and down around the 2000rpm mark, it's especially noticeable when driving at higher speeds. Eventually the revs start decreasing and stabilize. I have cleaned the throttle body etc. and changed the T-map for a replacement used one. The car does seem a bit more responsive with the replacement T-map but I'm still having the same issue (with the old T-map it also used to rev highly around 3000rpm when putting it into park before stabilizing but that problem seems to have gone). Does anyone have an idea what the issue is? Could be that I need to replace T-Map with a new one or it may be something else altogether?

Thanks Paul.

[rondeo]

Fault codes?


Accelerator pedal, is it mechanical or electronic as in 2007 + ?




What's T map?

[cobrin]

Behaviour like that reminds me of a vacuum leak, best time to use a smoke machine lol. You could dot spray brakekleen around the intake system and see if the rpm changes, or use an obd scanner and look at intake map readings or exhaust O2 readings.


Or take it to a workshop to diagnose.

[Metdevil]

Sounds like what mine was doing when it had a split PCV hose.
The hose is very hard to see, situated between the intake manifold and the engine block, so it's quite difficult to confirm.
If you can look between the gap at the right angle you might be able to see it.

[Crazy Dazz]

when you say "coast" do you mean no throttle at all? ie engine-braking?
or are you using the cruise-control?

if you are actually coasting, the car will slow down, the transmission will change up, and revs will drop.

Also, what type of tranny does your model have?
Older conventional trannies with lock-up toque-convertors often do funny things like that, as they keep flicking the clutch in and out.
On the other hand if it has a powershart, then anything is possible

If your transmission has a "sports" mode, try engaging that as it will usually turn off any lockup function.

[Metdevil]

Originally Posted by Crazy Dazz

when you say "coast" do you mean no throttle at all? ie engine-braking?
or are you using the cruise-control?

if you are actually coasting, the car will slow down, the transmission will change up, and revs will drop.

I think mine had the same problem. If you were 'coasting' at 50km/h, the revs were so high that you would actually pick up speed. Driving around town, we would have to ride the brake to maintain 50km/h.

It wasn't so drastic at highway speeds, you'd lose speed as you should if you took your foot off the pedal, though the revs were still higher than they should be.

[paul r w]

Hi, thanks for the responses, here's some answers to the questions:
it's a mechanical accelerator
the t-map is the equivalent of a MAF mass airflow sensor
it's an automatic gearbox
by coasting I mean taking my foot off the accelerator while still in D drive
auto gearbox has an overdrive option which is similar to sports mode (stays in lower gears longer), using this doesn't make any difference.
symptom's are - in drive, take foot off accelerator, revs start bouncing up and down and eventually settle.

[Crazy Dazz]

Originally Posted by paul r w

Hi, thanks for the responses, here's some answers to the questions:
it's a mechanical accelerator
the t-map is the equivalent of a MAF mass airflow sensor
it's an automatic gearbox
by coasting I mean taking my foot off the accelerator while still in D drive
auto gearbox has an overdrive option which is similar to sports mode (stays in lower gears longer), using this doesn't make any difference.
symptom's are - in drive, take foot off accelerator, revs start bouncing up and down and eventually settle.

Is it a conventional auto or a DSG?
If you shift into neutral, is the problem better or worse?
can you replicate it when stationary in neutral or park? eg rev it up to the problem range, back off, and see what happens.

I'm far from being expert on the Mondeo, although I believe I have a very similar engine in my XR4 (2L Duratec)
So check this for yourself, but I think that by 2006 Ford had mostly fixed the Swirl-Flaps, but they were still being used.
So I'd try to check that they are working, and not too noisy. Thoroughly check all your vacuum lines and gaskets for leaks. Give your throttle body and sensors a good clean.
Sorry I can't really offer anything specific.
You could cheek out this guy, he has some good videos on his Mondeo

[paul r w]

Originally Posted by Crazy Dazz

Is it a conventional auto or a DSG?
If you shift into neutral, is the problem better or worse?
can you replicate it when stationary in neutral or park? eg rev it up to the problem range, back off, and see what happens.

I'm far from being expert on the Mondeo, although I believe I have a very similar engine in my XR4 (2L Duratec)
So check this for yourself, but I think that by 2006 Ford had mostly fixed the Swirl-Flaps, but they were still being used.
So I'd try to check that they are working, and not too noisy. Thoroughly check all your vacuum lines and gaskets for leaks. Give your throttle body and sensors a good clean.
Sorry I can't really offer anything specific.
You could cheek out this guy, he has some good videos on his Mondeo

It's a conventional auto
additional to the rev problem described is that the revs are erratic, sometimes when cruising at a stable speed they bounce up and down,
revs can also stick at a high rev level for a few seconds before dropping down & when I stop and put in park it idles around 1000
but when I put my foot on the accelerator and take it off the revs stick at 3000 for about 5 seconds before dropping.
I used the videos for throttle body and T Map cleaning and did this a couple of weeks ago and it made no difference,
changed the T Map after that, car is more responsive but revs problem still persists. At this stage from the info provided
it looks like I need to check the swirl flaps aren't sticking and see if I can detect any splits in the hoses?

[Crazy Dazz]

Originally Posted by paul r w

but when I put my foot on the accelerator and take it off the revs stick at 3000 for about 5 seconds before dropping.

Have you observed the operation of the throttle when this happens?
(In an otherwise perfect engine, a sticking throttle cable could cause something like this)
If the throttle is closing, but revs take a while to drop, that strongly suggests that you have a vacuum leak somewhere, so the engine is still sucking in too much air.
With a modern EFI engine that can cause the instability you describe, as the computer struggles to adjust the mixture.

Those swirl flaps add another layer of complexity, and they are also controlled by a vacuum actuator.

[paul r w]

Sorry for the delay in responding, I've only just got it fixed.
The cause of the problems were:

PVC Hose split at intake manifold, intake manifold needed to be removed to access the pipe and replace (note: pipe difficult to see behind the manifold).
Idle stepper motor was faulty as well due to being overworked through the excess air issue. When the pipe was replaced it wouldn't return to normal speed settings & was stuck at high speed.
Manifold seals also renewed at time of repair as these had signs of wear.

Regards Paul

[Fast Eddie]

Hi Paul, I too own a EuroFord (MKI Focus) and have similar symptoms. When you say Idle Stepper Motor would this be the same as the Idle Control Valve?

[paul r w]

Hi, they seem to have the same name, its this part in the attachment: