Technical Fiat Ducato 3.0 jtd 160 multijet throttle/EGR error

[sheridantony]

Reviewing the various threads I understand this is a common issue?

I have a 2007 Burstner i685 Elegance motorhome with the 3.0 litre turbo diesel engine. The engine has started 'hunting', mainly once the engine has warmed up. Have had a carbon clean, service, new fuel and air filters, as well as a fuel additive used by garages themselves. Nothing worked.

Put it on an OBD Reader and diagnosed with the attached faults i.e:
PO638 - Throttle valve control, short circuit to ground, intermittent.
PO401 - Exhaust Gas Recirculation (EGR) valve, Closed, locked, intermittent.

I am being quoted £430.00+VAT for a replacement throttle valve/unit + labour. This is an original Fiat part.

This seems a little excessive? Has anyone sourced this part themselves for cheaper? If so can you let me know where you got the part from please? Also whether a replacement throttle body will resolve both faults.

Many thanks for any advice and guidance you can provide.

 

[bugsymike]

Maybe others can advise better , but my thoughts would be directed towards the EGR side, especially as fault happens more when warmed up.
Some diagnostic tools can power up individual units to test things like the EGR valve and given age / mileage ? possibly choked up, so testing it at least may be a cheaper option to start with.

 

[taffybloke]

As bugsymike said it sounds as though the problem is EGR related, the vacuum control valve for the EGR is usually situated under the scuttle on Fiat Cabs and it often fails causing the symptoms you give. The throttle body and inlet manifold can get chocked up with the deposits the EGR sends back to it so it's worth cleaning if you can. A member (techno) on the Motorhome fun forum posted about the throttle body and EGR issues a few years ago along with the water ingress problems. It's worth a search on there for his posts.

The Throttle body in the earlier 3.0 was a Wahle unit then replaced with a better Pierburg unit.

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It may need an adapter cable.

https://www.ebay.co.uk/itm/Fiat-Duc...le504388738-/272836500860?hash=item3f86529d7c

if ordering these make sure they fit your engine.

 

[sheridantony]

As bugsymike said it sounds as though the problem is EGR related, the vacuum control valve for the EGR is usually situated under the scuttle on Fiat Cabs and it often fails causing the symptoms you give. The throttle body and inlet manifold can get chocked up with the deposits the EGR sends back to it so it's worth cleaning if you can. A member (techno) on the Motorhome fun forum posted about the throttle body and EGR issues a few years ago along with the water ingress problems. It's worth a search on there for his posts.

The Throttle body in the earlier 3.0 was a Wahle unit then replaced with a better Pierburg unit.

7.01754.10.0 PIERBURG for sale | eBay

Find great deals on eBay for 7.01754.10.0 PIERBURG. Shop with confidence.

www.ebay.co.uk

It may need an adapter cable.

https://www.ebay.co.uk/itm/Fiat-Duc...le504388738-/272836500860?hash=item3f86529d7c

if ordering these make sure they fit your engine.

Hi, many thanks. Actually just back from the garage having had the throttle body replaced. Sourced a new body from Coastal Motorhomes, the upgraded one with the adapter cable. Just ran her back home for 35 mins and no sign of the hunting at idle, nor any error codes in system. Won't be convinced until after she's had a proper run though, and already spoken to the garage about EGR replacement if this hasn't sorted it. Got the whole job done for over half the price originally quoted by Fiat, and have kept the old throttle body in case that wasn't the issue. Fingers crossed no more problems.

 

[sheridantony]

Hi. So just back from a month long trip and over 1000 miles and seeking further advice on next steps. Should I replace the EGR valve next?

To summarise.

2007 Fiat/Ivenco 3.0L Multijet 160 diesel engine with 51000 miles. Had engine management light and engine 'hunting' once warmed up. Technician decoked engine, and OBD reader diagnosed faulty electrical circuit on throttle body. Replaced throttle body with new (apparently upgraded) part. Garage added fuel cleaner and I have followed up with Redex each time I've added fuel since the part was replaced. Engine runs quite smooth now, but still 'hunts' once warm and going over 65mph. Idle when warm still a bit hit and miss. Doesn't misbehave when cold or below 65mph (only get to that speed when overtaking lorries).

Obviously try not to go over 65mph now if I can help it.

Any idea what the root cause continues to be?

 

[bugsymike]

Hi. So just back from a month long trip and over 1000 miles and seeking further advice on next steps. Should I replace the EGR valve next?

To summarise.

2007 Fiat/Ivenco 3.0L Multijet 160 diesel engine with 51000 miles. Had engine management light and engine 'hunting' once warmed up. Technician decoked engine, and OBD reader diagnosed faulty electrical circuit on throttle body. Replaced throttle body with new (apparently upgraded) part. Garage added fuel cleaner and I have followed up with Redex each time I've added fuel since the part was replaced. Engine runs quite smooth now, but still 'hunts' once warm and going over 65mph. Idle when warm still a bit hit and miss. Doesn't misbehave when cold or below 65mph (only get to that speed when overtaking lorries).

Obviously try not to go over 65mph now if I can help it.

Any idea what the root cause continues to be?

Just to throw another "curve ball" recently talking to a retired Fiat Motor Home mechanic and he mentioned one of the most common faults he has had is faulty/unreliable DPF pressure sensors at the end of the pipes from the DPF, to the point that they are one of the first things they replace.

 

[sheridantony]

Just to throw another "curve ball" recently talking to a retired Fiat Motor Home mechanic and he mentioned one of the most common faults he has had is faulty/unreliable DPF pressure sensors at the end of the pipes from the DPF, to the point that they are one of the first things they replace.

Soooooo, EGF and DPF pressure sensors, got it. So which to replace first? Or do I try decoking her again as it's cheaper?

 

[bugsymike]

Soooooo, EGF and DPF pressure sensors, got it. So which to replace first? Or do I try decoking her again as it's cheaper?

See what your garage advises, I always liked to justify what I spent on my customers behalf.

 

[Kimpa]

Soooooo, EGF and DPF pressure sensors, got it. So which to replace first? Or do I try decoking her again as it's cheaper?

How did this end?
I have exactly the same problem and the same engine 3.0 mjt.
I have done the same steps, trottlevalve changed and then the hunting started.
Since then i have change the Egr valve.
I have had it to 2 diffrent garages but both of then could not find the problem.

 

[MillieTheMotorhome]

I had the same problem 2 years ago when P0638 fault surfaced. I replaced the throttle body with one from an eBay seller that looked identical and cleared the fautl code but the engine hunted quite a lot. Cleaned the EGR valve, it's mechanical and unlikely to fail in my opinion, with no inprovement. Changed the solenoid valve that controls the EGR, again with no improvement. Had it looked at by 2 garages, one I really trust and another that was recomended, but nobody could find the cause of the hunting. Finally forked out a kings ransome for a genuine Fiat replacement from a Fiat Dealer, fitted it and hey presto, problem solved. BUT, just under 2 years later and the dreaded P0638 code has just popped up again so I've just taken the throttle body off and will take it to the Fiat Dealer and see what they have to say. Probably "Give us some more money and we'll give you another one".
One thing I did notice, as mentioned above, is that where the cable socket enters the body there looks to be some corrosion and I think water drips down onto it from a guard plate above it. The connector itself looks fine but I suspect water has found its way inside the throttle body electronics and caused it to fail.