Technical Engine revs falling down a hole !

[Road Sailor]

Hi, we have a 2001 Ducato motorhome manual gears. The engine has developed a fault, going up through 1st and 2nd gear is fine, speed is building nicely, however when changing up to 3rd, 4th the engine revs plummet, not good when you have traffic behind you or going up hill. However when the revs increase again the van goes really well in top gear. We have changed the fuel filter, had the turbo checked, had the ECU sent away and checked, had the throttle pedal changed. Annoyingly the Fiat dealership garages do not have the software to plug into the socket so we have no idea what error codes there may be. We feel it must be something really simple . Has anyone experienced this or any ideas of what the problem could be? Thanks
Cathy

 

[Road Sailor]

I know nothing much about your cruise control system , however if fault occurred after battery replaced in cruise control, perhaps try disconnecting that battery. I appreciate you have mentioned that garage has disconnected cruise control from the system , however it could still be affecting things due to a defective wire or something.
On a slightly different note, was the original cruise control battery faulty or disconnected by the previous seller, as from the sound of it you are very honourable people, but not all are.

ok, so he says it was the battery in the key fob remote control for the cruise control that he replaced …. but as we have never actually driven it more than a few miles close to our home in Norfolk, then cruise control never really ever got tested.

 

[bugsymike]

ok, so he says it was the battery in the key fob remote control for the cruise control that he replaced …. but as we have never actually driven it more than a few miles close to our home in Norfolk, then cruise control never really ever got tested.

As I say, I know nothing about your cruise control system, but I can't see the logic of something that affects the speed of a vehicle that has the ability to be controlled from an external remote control, but maybe someone else on Forum knows more on the subject.

 

[varesecrazy]

Thanks Mike, we are right over in Norfolk!

@The Panda Nut is near Dereham

 

[Road Sailor]

@The Panda Nut is near Dereham

Thank you

 

[The Panda Nut]

I have had several cars with cruise control and have looked at after market systems as well. I think the notion of the remote control battery for door locks or alarm being in any way linked to the cruise control is nonsense. I had odd issues with the cruise control on my Bravo not functioning, but turning it of and restarting always reset things.
Which Fiat garaged have you tried. You probably need a Fiat Professional Garage. I couldnt recommend Motorvogue in Norwich from my own experience howeverand their hourly rates are worse than shocking.
I do have MES and would be happy to try and see what it might tell assuming it stops raining for long enough... If you would like to do this please send a message on here and we can sort something out.

 

[Road Sailor]

I have had several cars with cruise control and have looked at after market systems as well. I think the notion of the remote control battery for door locks or alarm being in any way linked to the cruise control is nonsense. I had odd issues with the cruise control on my Bravo not functioning, but turning it of and restarting always reset things.
Which Fiat garaged have you tried. You probably need a Fiat Professional Garage. I couldnt recommend Motorvogue in Norwich from my own experience howeverand their hourly rates are worse than shocking.
I do have MES and would be happy to try and see what it might tell assuming it stops raining for long enough... If you would like to do this please send a message on here and we can sort something out.

Thank you very much. As I explained earlier in the thread, we have sold the motorhome to another Norfolk couple because we don’t have the driving licence to drive 3.8. We have a friend with trade plates who has kindly taken it to two local independent garages and also the Fiat garage in Diss. They did not have any way of reading the codes despite us giving them the adapter plug they say the vehicle is too old (2001), they couldn’t even give us a wiring diagram . We want to do right for the couple that have bought it from us and feel sure that the issue is likely very simple, however we have spent hundreds of pounds getting things tested and different ideas explored. We have got it booked in to Allstarts Diesel garage on Sweet Briar on Wednesday our friend is going to take it there on Tuesday afternoon. Perhaps if we don’t get a solution with them, we can come back to you? My husband Brad says that the cruise control is a red herring . I’m the one that’s obsessing that there is a connection with the CC and the engine RPM. We do plan to go the garage where it is currently stored and check the blue electric connector for corrosion as mentioned in another post.

 

[The Panda Nut]

Ok. I am uncertain if my mes will connect but will certainly try. Fingers crossed for the next garage.

 

[Road Sailor]

I would like to add that it has an aftermarket John Gold cruise control fitted. One of the garages have assured me that they disconnected it, because I thought it may be causing the issue…

Hi guys , well it seems my hunch was right. The diesel specialist ran lots of checks and found that the aftermarket cruise control had not been full removed and it was causing the problem, is cost us a further £600 in labour charges but such a relief, and so pleased for the guy that we sold it to .

 

[Eirediver]

I am having a similar issue as you were having.

What was the issue with the cruise control that was causing this issue? And what did you do to fix it?

Was this only happening when the cruise control was engaged or all times?

 

[Ocwobio]

Given that the problem is associated with gear changing, I have developed a niggling thought that it could be a sticking clutch pedal switch (sensor). However I am not sure whether this would match the symptoms, or go the other way. Unfortunately I do not have time to check on this until this evening.

I have heard of those who are equipped with large 'plates of meat' (feet) brushing the brake pedal when using the clutch. If it is set up such that it needs the merest movement of the pedal to just flick said switch, it can cause a momentary power loss. Maybe I'm dreaming this, but I'm sure it does not recover instantly, there being a programmed time delay of sorts applied to it?