My 2000 V6 Viano 'Hunts'

[DaveMargetts]

I have a v6 2.8 litre Japanese import Viano minivan that starts well, but as soon as I press the accelerator pedal, the engine stalls. If I wait for it to warm up, it seems to rev up quite normally but there's a distinct 'hunting' in the revs at idle and at any other rev range. I can't see any leaks in the vacuum hoses (that I can see). A local garage identified the Mass airflow unit as faulty and replaced it but according to them, it's still showing a MAFS fault and possibly a throttle body fault. I've cleaned out the throttle body and it looks OK to me. My diagnostic tool will unfortunately not connect with the van's computer, so I've not been able to interrogate the fault codes any further. Has anyone got any suggestions?
I should add that I've replaced all 6 spark plugs, the air filter and the fuel filter. I also hooked up a strobe to the HT leads and all 6 seem to be firing as they should.

 

[m80]

I would confirm continuity from the ECU to the MAF.
The pins at plugs can flare, sometimes due to others pushing probes in forcefully to test.
Of course for that you need a DVM and to understand which points in the ECU to test from. Star would detail how to test.

 

[DaveMargetts]

I would confirm continuity from the ECU to the MAF.
The pins at plugs can flare, sometimes due to others pushing probes in forcefully to test.
Of course for that you need a DVM and to understand which points in the ECU to test from. Star would detail how to test.

Thanks for the reply - do you know of a reasonably prices diagnostic tool that will talk to my van? I have one of those 'Bluetooth ones' that works via a phone App, and I know it works as it's fine with my Citroen, but when insert it into the van, it just reports back that it cannot see the Van's computer. Also - do you know where I might find the ECU on a 2000 Viano?

 

[DaveMargetts]

I would confirm continuity from the ECU to the MAF.
The pins at plugs can flare, sometimes due to others pushing probes in forcefully to test.
Of course for that you need a DVM and to understand which points in the ECU to test from. Star would detail how to test.

Also - High Peak Derby sounds like a lovely place to live!

 

[BTB 500]

This is a W638 V280 (V Class) and not a Viano - it's based on VW's FWD floorpan and has the original 12 valve version of the Volkswagen VR6 engine. The Viano was the MPV version of the later (and completely different) RWD W639. As an early '90s design W638 diagnostics will likely be a bit more rudimentary (as per my R129 SL I assume). Of course the VR6 was widely used in VW models so it might be worth a quick look for similar issues with those??

 

[m80]

Thanks for the reply - do you know of a reasonably prices diagnostic tool that will talk to my van? I have one of those 'Bluetooth ones' that works via a phone App, and I know it works as it's fine with my Citroen, but when insert it into the van, it just reports back that it cannot see the Van's computer. Also - do you know where I might find the ECU on a 2000 Viano?

That'll be a 638, sorry I've no experience of those. My experience is of the 639.

On the 639 there is an under bonnet enclosure.
That contains fuse rails and relays,
also in there is the SAM, ECU and if applicable the TCU. I don't know if the 638 is similar.

For simple monitoring I use an EML327 BT sender. That communicates with the 'Torque' app on an android.
It isn't comprehensive, but very useful. It does detail faults, and shows live readings for many things, but limited.
Very likely the OBD communications of the 638 would be further limiting.

W.o Star to detail the pin outs it is possible to peel back at the MAF and identify wire colours. You could then attempt to match those at the ECU, but that can be confusing.
Of course you could unplug at both ends and test wire continuity, but some wires will double up to 2 or more sensors, so that's not a guarantee, as you might be testing through a sensor, so wire colours is more reliable.

 

[DaveMargetts]

This is a W638 V280 (V Class) and not a Viano - it's based on VW's FWD floorpan and has the original 12 valve version of the Volkswagen VR6 engine. The Viano was the MPV version of the later (and completely different) RWD W639. As an early '90s design W638 diagnostics will likely be a bit more rudimentary (as per my R129 SL I assume). Of course the VR6 was widely used in VW models so it might be worth a quick look for similar issues with those??

Thanks - You are correct, it's definitely a FWD W638 as the VIN shows that when I put it into the Mercedes service software. Mine was a Japanese minibus before being converted into a campervan (according to the previous owner). I'll certainly look at VW as well

 

[BTB 500]

Mine was a Japanese minibus before being converted into a campervan (according to the previous owner). I'll certainly look at VW as well

The minibus version was the (less plush) Vito Traveliner, but I'm not sure that was available with the petrol V6. W638s were never galvanised so most UK ones have rusted away but hopefully an import will be better! As an aside there will likely be some minor differences in the wiring, but I would guess the engine loom(s) would be the same as UK spec.

Hope you get to the bottom of it - good luck!