Fast Idle & White Smoke

**seancook1983** · 05-06-2020,05:55 PM

Hi all hope everyone is doing well in the current situation? I just want to pick someones brains lol

Ok so I have a mk6 Golf TDI 110bhp CBDC engine and it started giving me issues about 4 months ago and I have since been trying my hardest to figure out what is causing it. The issue is the car starts perfect and idles perfect in drive the drive way, as soon as I drive lets say over 25mph or 2500rpm and then stop come to a halt the idle sits at 1000rpm and if I the drive I'm getting white / light grey smoke bellowing out the back if I sit in any gear at around 2000rpm, if I increase speed to 3000rpm the smoke stops it only seem to smoke at a specific RPM in 2nd 3rd & 4th not so much in 5th. if I unplug the MAF sensors the car does not do it at all its drives perfect but obviously a MIL light on the dash and loss of MPG. before I go and spend £140 on a new Bosch MAF sensor what are the chances of the MAF sensor causing fast idle and white smoke? its not head gasket as coolant has not been topped up in over a year and is still between min & max, I've rules out turbo oil seals as its not use hardly any oil in past 4 months since smoke started.

VCDS does not return any codes at all so its really bugging me as to what it can be, so any suggestions or help would be much appreciated thank you. before I take a blow torch to it lol

**Crasher** · 05-06-2020,07:46 PM

Only fit a genuine VAG Air Mass Meter bought from a VW dealer or TPS, 03G 906 461 C which is £149.77 retail including VAT.

**seancook1983** · 05-06-2020,07:49 PM

Is it poss that a faulty MAF would cause white smoke? and fast idle tho. as don't want to but a new MAF if its not the issue. as they said electrical parts can not be returned. thank you

**Crasher** · 05-06-2020,09:39 PM

In my experience the most likely cause is blocked injectors caused by high pressure fuel pump failure.

**seancook1983** · 05-06-2020,10:19 PM

I have thought maybe injector issue but the fact unplugging MAF sensor makes the white smoke stop I'm not sure how the 2 can be connected.

**Roverfan** · 06-06-2020,12:11 AM

Out of interest is the idle still at 1000rpm with MAF disconnected and when it is idling fast is it stable?
Any remaps?

**seancook1983** · 06-06-2020,09:13 AM

Originally Posted by Roverfan

Out of interest is the idle still at 1000rpm with MAF disconnected and when it is idling fast is it stable?
Any remaps?

No if I unplug the MAF and drive around the car idles perfect around 780rpm and I get no white smoke at all, if I switch the car off, plug MAF back in and take car up the road as soon as I go over 25mph or 2500rpm the car will then idle at 1000rpm and chuck out white smoke when I reach 2000/2500rpm in 2nd,3rd & 4th gear. The smoke is constant if I stay at a set Rev range for example if I cruise as 2000rpm in let’s say 3rd gear the smoke will continue to come out the back and it’s very dangerous for drivers behind me, if I then put my foot down to say 3500rpm the smoke stops, as it’s only at a certain rpm the smoke happens

**Crasher** · 06-06-2020,11:14 AM

I would say it is likely to be one or more injectors so personally I would spend some time studying the measuring block data looking for clues and use the test tools provided by VCDS to check the Air Mass Meter plausibility but I have never replaced one on a CR engine, the modern ones seem to be extremely reliable but I have lost count of the number of CR injectors I have replaced. Unplugging the AMM will send the ECU into a lower fuelling default mode which can mask faulty injectors.

**philipharmes** · 06-06-2020,11:27 AM

When you mention the speed & revs it sounds as though the car is trying to do a regen of the DPF.

My wife's 2l 140 CBAB Passat sometimes smokes like this if trying to do a regen around town, it gets a lot of town use.

Once a regen starts the revs rise to 1000.
Also unplugging the MAF would stop a regen taking place.

Does the car ever get a good run of at least 10 miles of 40+ MPH running with a hot engine ?

**seancook1983** · 06-06-2020,07:38 PM

So I took car for a long drive today for 50 miles as I have only done short journeys the past month or so so wanted to give it a good run. Soon as I got back I thought I would check the injector values and they seem ok to me but I did notice the fuel temp seems low to me after a hour drive up the motorway. Fuel temp is reading at 40c is this about right for a long journey? Or should it be higher?