Golf mk4 2.0 gti running rich

[VW NORTON]

My golf 2.0 gti mk4 has gradually been using more fuel.i am currently getting approx 18mpg.there is excessive black smoke and petrol fumes from exhaust.the idle is also not good.when the car is ticking over the fuel computer displays 15mpg when it used to be at zero.should i start with the lambda sensor? Any suggestions will be helpful.
Thanks

[Crasher]

No you should start with a fault code read. The three most common cause of this problem on your engine are the lambda sensor, the Air Mass Meter or the coolant temperature sensor but you will have no idea where to start without a code read.

[VW NORTON]

O.K ,will get check.Should I be getting any fault light on?

[Crasher]

It depends on the year and engine type code.

[vw_craig]

I didn't have the smoke issue but when I bought my 2.0 gti I first changed the fuel filter and air filter and cleaned the MAF sensor with contact cleaner from maplin. Got an instant jump in MPG. crusing on the motorway 60/70 was giving me 35ish and local journeys mid 20's to 30. Then with the cold recently I have have sludge build up in the oil breather. Due to the icy weather and short journeys not burning off the condensation in the engine its dropped again. So as I replace gaskets 1 by 1 to try and solve the air gap I keep cleaning out the breather pipes coming from the rocker and to air filter pipe and cleaning the MAF sensor at the same time. My car bubbles at just under 800 rpm on iddle...not sure if that's right. Also check your spark plugs, they may give you a good indication of oil buring / rich fuel so on.....

[VW NORTON]

sounds as though we have same problems.my car also does short journeys and i also get a bit of the old sludge.i replaced the lambda sensor yesterday and it seems to have cured fault.the thing that bothers me though is if something else is wrong.my fuel computer showed better mpg straight away but it wont zero.does yours zero when u let off throttle?mine reads 5mpg at idle but when stopping just stays at last reading.i was thinking of cleaning maf,is it straight forward?

[Sam]

What was the result of the fault code scan?

[vw_craig]

sounds as though we have same problems.my car also does short journeys and i also get a bit of the old sludge.i replaced the lambda sensor yesterday and it seems to have cured fault.the thing that bothers me though is if something else is wrong.my fuel computer showed better mpg straight away but it wont zero.does yours zero when u let off throttle?mine reads 5mpg at idle but when stopping just stays at last reading.i was thinking of cleaning maf,is it straight forward?

I was thinking about doing the lamda as well, seemed awkward to change form above, did you jack it up and go underneath?? Is it fairly straight forward and how much is a replacement?

Since replacing my oil breather assembley attached to the rocker and cleaninf all pipes and MAF again. Car runs great but the trip is saying poor MPG, even though the state of the issue is alot better! another check of pipes and so on tom I think. :(

The trip says random MPG numbers everytime I stop. But the average drops like a bomb now when I am at a standstill, its like countdown!

The MAF is very simple to clean and take out. You don't take it out itself but in the housing its in which connects to the air filter and air pipe. Solid plastic, just take it out, clip one side and 2 phillips screws the other, unplug the connector first. Hold it and spray lightly both ends from distance the sensor is side and let it dry before replacing. I use SERVISOL super 10 - switch cleaning lubricant, from maplin. Its less than £6.

[VW NORTON]

Cleaned maf a couple of days ago,it didnt look dirty but was well worth it.I can not believe how much more power the car has now,i cant remember it ever running as well! Anyway,had fault read on it today and looks like the other 02 sensor needs doing now,this is the one that is after the cat.Cost me £40,gonna fit it on monday.I would definitly recommend fitting the sensor yourself if your half decent with your hands.I did buy the pucker tool for getting it out,it cost me £9 and was worth every penny cos it loosened it easily.Its a bit tight but only seems possible to attack it from above but get some ramps cos the sensor plug is located underneath car in line with the cat.

[vw_craig]

Glad the MAF sensor clean went well! and successfull. After another full clean and positive running results. Car is struggling to climb over 20mpg without really touching the pedal! Very fustrating. I don't have the money to changet the Lambda sensor unless it's defo the problem so I guess my next plan of action is to find a nice person somewhere in Surrey with a VAG com to help me out to see what's going wrong. Or a cheap VW specialist close to Gatwick area.........

Wondering if the MAF has gone now possibly as well.....Love the car but too many sleepless nights since buying it from a cheeky garage who stiched me right up with too many problems!

[VW NORTON]

Hello Craig,I paid £20 for reading,its got to be worth it cos your gonna be doing that in extra petrol in a couple of days.The way i understand it is that your car is using excess fuel cos your ecu is allowing too much through.This is probably caused by a faulty sensor.Is your car smoking more than usual/running rich?

[vw_craig]

It is running very rich! may as well be driving a v6 with my foot to the floor! ha

It does seem to be leaning towards a faulty lambda or MAF but I can't afford to change something which isn't faulty, hense the VAG com check. But my local garage who I trust don't do anything like that and I have been quoted £60 in the past by vw specialists....so I am trying to find a kind fellow owner with one or some friendly garage that would charge about £20 just for a plug in! But no good so far :(

Have noticed today a smell around the car and fuely type but clear exhuast fumes as well

[markf497]

I just got myself a 2000 mk4 gti 2.0 8v (APK engine code) 70k on the clock and i'm getting poor mpg probably about 20mpg thats driving easy, 160 miles to £40 I have vag-com and have the following errors
17536 Fuel Trim: Bank 1 (Mult): system too lean P1128 35-00
I also have 17987 Throttle Actuator (J338) Adaptation not started P1579 35-00.
I can clear the fuel trim code but it comes back but can't clear the Throttle code. When i got the car its idle was ok at cold but dropped when warm I removed the throttle body and gave it a good clean now the idle is ok but I stillcant clear the code. My main thing is the mpg I took out my MAF sensor and soaked it in IPA overnight dried it out but mpg still about the same would my throttle body allignment be causing poor mpg I also get some black smoke when putting accelerator hard. Any help appreciated is there a way to check my MAF sensor and O2 sensor with vag-com.

Thanks in Advance for any info.