Fault code P0638

[tidewatcher]

Management light came on after a very minor misfire that lasted seconds. Got the code read and it is the butterfly regulator, it only happpened after rain and when going over a bumpy part of the road. I fiddled about to see if anything was loose and sprayed with WD40 then started the engine few times. Next morning the light was out for a good few miles, stopped and went for a walk. When I restarted the light was on again but the motor running fine.

So in the camper van in France at the moment, tempted to drive it until either it remains the same and the engine runs fine or it gets worse and there is a definite fault to fix.

Having a bit of a dither as to how serious the problem may develop or just carry on with care. Is this a common problem?

Any experience in this problem would be appreciated.

 

[gus-lopez]

That sounds like the "rusty throttle body" caused by rain(any) water running down & entering the throttle body. Plenty of threads on here about it. If you can dr it out/keep dry should be ok until you get home .Also needs the rain cover to prevent it happening fitted

 

[jerryz]

Its the Throttle valve actuator mine my 2009 fiat did it for 6 months I just reset it ,but eventually it will die and strand you so change it soon the Part is £234 from Coastal Motorhomes,, I did it myself ,its only held in by 4 bolts but they rust into the block i had to drill 2 of them out and re tap the threads ,, job time if no busted bolts 1 hour , with busted bolts 4 hours , but my van now runs sweetly ,
, A fiat dealer will charge you £1200, and independent about £700 plus Vat

 

[tidewatcher]

Its the Throttle valve actuator mine my 2009 fiat did it for 6 months I just reset it ,but eventually it will die and strand you so change it soon the Part is £234 from Coastal Motorhomes,, I did it myself ,its only held in by 4 bolts but they rust into the block i had to drill 2 of them out and re tap the threads ,, job time if no busted bolts 1 hour , with busted bolts 4 hours , but my van now runs sweetly ,
, A fiat dealer will charge you £1200, and independent about £700 plus Vat

Thanks. Just came on for the first time so fingers crossed as in France for four weeks more. Restricting mileage which is no real problem along the dordogne and Gironde area as plenty to see. Does take the edge of the enjoyment though.

 

[tidewatcher]

OK so hobsons choice really. Drive it and keep mileage down to a sensible level ( Pyrenees binned for this trip) and if it does get worse bite the bullet and find a local repairer. Have breakdown cover if it does gasp it’s last to get us to a repairer. Luckily in the wine region….

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[gus-lopez]

Or spray all around it with wd40 regularly, then spray the 4 bolts daily with penetrating oil to ensure they will come out when you want

 

[Landy Andy]

Just keep doing what ever you want, and deal with it, when or if t happens.

 

[tidewatcher]

did some wire wiggling the a good dose of WD40 around the area and light didn’t come on this morning. First start of engine after turning off with light on. Didn’t do the five or so restarts. I think it’s little electronic brain is messing with me.

 

[tidewatcher]

And the latest is… got the van home from France though it was not a relaxing journey. Light came on again and some misfiring. Have now removed the throttle body, the butterfly is free and no signs of sticking. There does not seem to be any water ingress into the actuator area, however there is a big build up of soot in the body itself and also the inlet manifold below it. So, how to test the actuator, why is there such a build up of sooty deposits?

 

[Jimbohorlicks]

Some info here if it helps

https://www.aulro.com/afvb/the-verandah/276914-what-causes-inlet-manifold-deposits-how-do-you-avoid-them.html

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[Landy Andy]

And the latest is… got the van home from France though it was not a relaxing journey. Light came on again and some misfiring. Have now removed the throttle body, the butterfly is free and no signs of sticking. There does not seem to be any water ingress into the actuator area, however there is a big build up of soot in the body itself and also the inlet manifold below it. So, how to test the actuator, why is there such a build up of sooty deposits?

The reason you have all that soot in there is to save the world apparently. You have a connection between the very dirty exhaust to the “clean air” intake of the engine. The great design/idea of an EGR valve.

The soot also will have covered your MAP sensor which you can now get to as you’ve got the TB off.

Whilst the TB is off put a tight sealed pipe up the EGR cooler exit, and see if you can blow through it. This will let you know if it is stuck open, then by fiddling with the EGR valve, test if it opens. You may well find it stuck open. Hence your problems.

 

[jerryz]

did you have any problems getting the 4,,,,,,, 8m bolts out ???without any shearing off

 

[tidewatcher]

Bolts came out reasonably ok but had been soaking in wd40 regularly. Having said that I did need a cranked ring spanner and some swearing to do it. Thanks

 

[tidewatcher]

The reason you have all that soot in there is to save the world apparently. You have a connection between the very dirty exhaust to the “clean air” intake of the engine. The great design/idea of an EGR valve.

The soot also will have covered your MAP sensor which you can now get to as you’ve got the TB off.

Whilst the TB is off put a tight sealed pipe up the EGR cooler exit, and see if you can blow through it. This will let you know if it is stuck open, then by fiddling with the EGR valve, test if it opens. You may well find it stuck open. Hence your problems.

View attachment 965618

Thanks for that will give it a go. I still have the quandary of replacing the TB in case the electrics which are sealed are failing. I will let you know how I get on with the egr valve.

 

[Landy Andy]

Thanks for that will give it a go. I still have the quandary of replacing the TB in case the electrics which are sealed are failing. I will let you know how I get on with the egr valve.

I assume you are still on the old version, and wiring. Reason I ask is I’m surprised you gat all the bolts out.

I physically blanked my stuck open EGR, and then had it remapped out. Now no EGR and no warning lights so flies through the MOT.

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[tidewatcher]

OK for anyone on the edge of their seats here is an update. Decided to replace the throttle body with the Pier? One and the converter connector. It’s a bit tight but does go in, all in place and tightened up. Have replaced the map sensor and checked the egr valve on a vacuum gauge as operating. Now wondering about any re learning needed by the management unit. Do I just fire her up after cancelling the fault code? While familiar with both aircraft and vehicle engines I come from a time when all you needed was a good ear and a set of spanner’s….

 

[Landy Andy]

OK for anyone on the edge of their seats here is an update. Decided to replace the throttle body with the Pier? One and the converter connector. It’s a bit tight but does go in, all in place and tightened up. Have replaced the map sensor and checked the egr valve on a vacuum gauge as operating. Now wondering about any re learning needed by the management unit. Do I just fire her up after cancelling the fault code? While familiar with both aircraft and vehicle engines I come from a time when all you needed was a good ear and a set of spanner’s…

Just drive it. It will learn what you have and adjust accordingly. The TB isn’t a critical part of the engine.

 

[tidewatcher]

Thanks for that, just needed a bit of reassurance. Thanks to one and all who have metaphorically held my hand through this rather testing disturbance. Every day is a school day…….

 

[L' Hobo]

Thanks for that, just needed a bit of reassurance. Thanks to one and all who have metaphorically held my hand through this rather testing disturbance. Every day is a school day…….

I'm presuming that the new TB was supplied with the new electric cable?
This is needed as the connections are slightly different.

 

[tidewatcher]

I'm presuming that the new TB was supplied with the new electric cable?
This is needed as the connections are slightly different.

Yup specified the converter cable needed. Like I said it’s a bit of a tight squeeze but overall seems to be a better build quality than the original. We will see…

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[jerryz]

When i replaced my TB i noticed soot i n the manifolds tried scraping and hoovering some out but inneffective ,, will just keep using REDEX in the fuel .

 

[jerryz]

I will have go at giving the EGR a service and clean but its a pain to get at on a Ducato ,,,, my van is running nicely now since the TB was changed

 

[tidewatcher]

Just when I thought it was all over…. Reassembled and started her up. Tick over not smooth, lumpy, a sort of hunting. Tried a drive and not happy with one backfire which took the pipe off the throttle body inlet, albeit it was held on with a flimsy clamp. Took her back and had a think. Got proper jubilee clip and then poured a dose of dpf cleaner into the tank which is less than half full. Started her up and as she got warm the tickover would be smooth then after revving lumpy. Couldn’t road test her again as the entrance to my garage was blocked. So…. Is it learning about the stuff just fitted? Has some of the soot and coke found its way to the dpf valve? Hey Ho. No management light comes on though!

 

[L' Hobo]

Just when I thought it was all over…. Reassembled and started her up. Tick over not smooth, lumpy, a sort of hunting. Tried a drive and not happy with one backfire which took the pipe off the throttle body inlet, albeit it was held on with a flimsy clamp. Took her back and had a think. Got proper jubilee clip and then poured a dose of dpf cleaner into the tank which is less than half full. Started her up and as she got warm the tickover would be smooth then after revving lumpy. Couldn’t road test her again as the entrance to my garage was blocked. So…. Is it learning about the stuff just fitted? Has some of the soot and coke found its way to the dpf valve? Hey Ho. No management light comes on though!

Probably have to change the valve behind the centre plate when you open the bonnet,that has the 2 pipes going to it as it has been working hard to compensate for the iffy TB.

 

[Landy Andy]

The TB is unlikely to cause any running problems on its own. It is only used for two things. It closes the air in when it wants to suck exhaust fumes via EGR, and when you turn your engine off to smooth out shut down. The rest of the time it isn’t doing anything. Throttle body is not really the correct term for it in my opinion. A true throttle body is on an a petrol engine not a diesel.

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[L' Hobo]

The TB is unlikely to cause any running problems on its own. It is only used for two things. It closes the air in when it wants to suck exhaust fumes via EGR, and when you turn your engine off to smooth out shut down. The rest of the time it isn’t doing anything. Throttle body is not really the correct term for it in my opinion. A true throttle body is on an a petrol engine not a diesel.

The old X250's TB's had the butterfly control mechanism at the BOTTOM and this allowed the water coming through the split in the scuttle to accumulate there and rust and sieze the mechanism.
The new TB has it positioned differently so this cannot happen but requires a different electrical connection wire.

 

[Landy Andy]

The old X250's TB's had the butterfly control mechanism at the BOTTOM and this allowed the water coming through the split in the scuttle to accumulate there and rust and sieze the mechanism.
The new TB has it positioned differently so this cannot happen but requires a different electrical connection wire.

Yes I know and have swapped between new and old before.

 

[Landy Andy]

Just when I thought it was all over…. Reassembled and started her up. Tick over not smooth, lumpy, a sort of hunting. Tried a drive and not happy with one backfire which took the pipe off the throttle body inlet, albeit it was held on with a flimsy clamp. Took her back and had a think. Got proper jubilee clip and then poured a dose of dpf cleaner into the tank which is less than half full. Started her up and as she got warm the tickover would be smooth then after revving lumpy. Couldn’t road test her again as the entrance to my garage was blocked. So…. Is it learning about the stuff just fitted? Has some of the soot and coke found its way to the dpf valve? Hey Ho. No management light comes on though!

When did the misfire happen? Under heavy acceleration?

Have you physically seen the TB flap shut/move?

 

[tidewatcher]

Ok will do a visual n the butterfly tomorrow and also order up the electro pneumatic valve as it’s an easy change. Thanks.

 

[tidewatcher]

OK ran the motor which was clean tickover until warm then the hunting again. Took the inlet pipe off the TB and when the engine was revved it opened and closed perfectly. Took the van for a run and a big improvement on yesterday, clean acceleration, no black smoke and it felt sharper but that may be because a lot of “touring weight” has been removed. Still hunts a little on tick over so will change the electro vacuum component, it’s an easy change and as has been said it has been working hard recently. Video of the odd tick over you can hear it with the sound turned up.

Could it be that the new unit and the management system have had to have a little chat to get to know each other? Anyway will see if changing controller for the dpf makes a difference. Nearly there…

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