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Discussion Starter #1
I know, I know its never gonna win any economy trials but she is now drinking so much that petrol is coming from the exhaust.

I recently had to replace 4 injectors and in the process discovered that the air box and intake pipework was broken in several places and beyond repair.
Original parts are a tad pricey, none on ebay and needing the bus back on the road I botched together a custom intake with a cone filter, flexi and steel pipes. I made sure all the vacuum connections & sensors are connected in the same places.
It ran silky smooth for a couple of weeks then one morning she started belching out blue/grey smoke and running rough.

I have taken her to the local VW specialist who cannot find anything wrong as such, no fault codes etc.
Driving as lean as I could on the way home still used 1/8th tank in 15 miles.
Placing hand over the tail pipe results in petrol on my hand.
Specialist says that it is due to the custom intake & the volume of air feeding false information to the ECU and confusing it.
I am not convinced because it ran well to begin with and logically thinking the MAF should tell the ECU the correct volume as it senses and the mixture adjusted accordingly.

Has anybody fitted a similar intake and kept things working correctly or have any ideas as to what could be the cause?

Thanks
 

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Okay, first thing first.. to get the best out of the VR6 you really need to be at the top of your game and I MEAN top of your game..

They are a tricky engine at the best of, so I'd suggest checking your MAF to see if its working, it would result on heavy fuel consumption.

Other possibility whilst I type is the Lamba probe.. they were notorious for eating them..

Lets get a look at the cobbled air intake - did you use larger pipe or what? even then as an engineer I can't see how that would trick the engine to over fuel. Over fueling may be caused by a cold start sensor not functioning correctly and from memory I believe there to be two, not that expensive either...the MAF ain't bad either so I'd look there..

I state "Top of your game" as in everything needs to be spot on as it a fussy bugger that needs to be loved, Magnicore leads are a great starting point to relive any misfires, a new coil pack is also beneficial again relives the cold start stumble until the morning.. but in short a really good tune up and correct plugs and you should be fine...

I used to be on the VR6 Forum and was the only person that could achieve text book mileage and I'm no slouch either - but was always tinkering.. these days I'm a diesel tinkerer now.. :(
 

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I would have thought:-

If your new air intake is leaky (after the MAF), as in letting air in, then the ECU wont get the right info but it ought to result in low fueling as a lower volume of air is measured passing the MAF

Presumably the MAF figures passed to the ECU are dependent upon it measuring air-flow in a pipe of known cross section, if you have fitted the MAF into something with smaller cross-section then it may give results suggesting more air is passing through and hence deliver more fuel.
 

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When you fitted the cone filter, I assume it's K&N type that needs oiling.
Did you follow the instructions and leave it 24 hours before using?
A fine film of oil on the MAF can ruin them (don't ask how I know!).
I ran OK for about 1000 miles before my MAF caused problems.
It's a sensor which is heated, and the air flow cools it to get a "number" to pass to the ECU.
A film of oil on the hot part confuses everything.
 

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Have you checked the condition of the vacuum hose from the ECU if there is one?
 

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Do these suffer from the same coolant temp sensor issues as the other petrols? That can cause over fueling if the sensor is telling the ECU that it's a lot colder than it actually is.

That said I would have thought that a dodgy coolant sensor would log an error code.
 

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Yes, and not always..

A temp sensor doesn't always log a fault as its deemed to menial.. only the one that says "I'm overheating" is registered...
 

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Get it on vagcom, after parking overnight all temp sensors should show the same temps.
Let it warm up at idle check for logical warm up.
Should be able to check lambda through Vagcom.
 

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Discussion Starter #9
Hi

Thank you all for your comments, I have finally been able to get out today and take a look.

I have replaced the MAF with one that was previously working. This has improved things (I think). It is still pumping out white smoke and running very rich, but the exhaust is dry.
I have also just replaced the intake temp sensor.
Lets get a look at the cobbled air intake - did you use larger pipe or what? even then as an engineer I can't see how that would trick the engine to over fuel. Over fueling may be caused by a cold start sensor not functioning correctly and from memory I believe there to be two, not that expensive either...the MAF ain't bad either so I'd look there..
The pipe is approx the same diameter as standard the same as the MAF diameter. Maybe a mm or two out.
I have replaced the COIL pack and leads with High Energy 10mm Race quality, so these should be ok.

When you fitted the cone filter, I assume it's K&N type that needs oiling.
Did you follow the instructions and leave it 24 hours before using?
The filter is unbranded cone, It has been left out in the workshop for a while before fitting.

I will check the coolant sensor next.

I did find that the secondary air system intake that as standard came of the air box down round the bottom of the engine to the secondary air pump has got a layer of oil or petrol inside.

I haven't been able to check the lambda yet but will do.
Thanks all for your suggestions, I will update with progress.
 

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Discussion Starter #11
Hi

Well after a busy month or so I managed to get back to sorting the bus.
Lambda sensor fixed the issue. Was still smoking for a while, but took for a drive and cleared within a mile, and now running fine.
I did find a thick film of oil on inside the intake which seemed to be coming from the secondary air pipe.
Being a little nervous and not wanting to blow another MAF i have now separated the secondary air inlet from the main intake and given it a filter all to itself.
Just done a 100 mile or so weekend away and ran faultlessly.

Is oil in the secondary air intake anything to worry about or could this just be down to the other issues?
 
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