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Model specific boards => Golf mk3 => Topic started by: Mboy on 14 March 2007, 19:53

Title: Over fuelling
Post by: Mboy on 14 March 2007, 19:53

Hi, I've got a 98 Mk 3 GTI which seems to be drinking to much juice, looked into it and signs are pointing towards the lambda sensor, if anyone else has any more answers could they please let me know,   thanks

Title: Re: Over fuelling
Post by: irmscher on 14 March 2007, 20:13

Can u not run diagnostics on it from the OBD?  I did with my dad's Primera, and it reported the front o2 sensor as being at fault.. The MIL was also on.  Not sure if the MK3's have an MIL? (Malfunction Indicator Lamp - orange light with the engine symbol)..

Have you been filling up with the dodgy Tesco/Morrisons fuel?

Title: Re: Over fuelling
Post by: EvilScotsman on 14 March 2007, 23:19

if you know anyone near you with vag-com, lambda should always read 1.00 at idle and cruise - and varies between 0.90 and 1.1 during acceleration and deceleration respectively.

If the lambda readings are low (weak mixture detected) then the sensor is calling for fuel it doesnt need. You can clean them but be gentle cos theyre fragile once unscrewed from the downpipe.

On some engines the Lambda probe is heated to speed up proper operation during cold running, maybe the heater suply is open circuit at the probe, broken wire etc.

Title: Re: Over fuelling
Post by: rubjonny on 15 March 2007, 09:56

the first thing you should replace if the car is over-fueling is the ECU temp sender, then the lambda :)
Don't buy cheap no-name lambdas either, I got one off ebay and it lasted 2 weeks.  Then bought a bosch universal one for £50 and its been fine ever since :)

Title: Re: Over fuelling
Post by: Mboy on 16 March 2007, 09:50

I've ordered a vag com of ebay so hopefully that should tell me a few answers, are lambda sensors easy to replace, they look just like a spark plug ?

Title: Re: Over fuelling
Post by: EvilScotsman on 17 March 2007, 11:39

They unscrew, prob tight too. Looks like a spark plug or lightbulb but they are fragile once removed. use wd40.

Title: Re: Over fuelling
Post by: mk3-ralf on 17 March 2007, 16:38

mate ive had the same problem...but mine has been fixed after i changed the spark plugs only did it yesterday so still keeping an eye on my petrol consumption...i was only getting 80miles out of £20 of petrol..so if you havent already done so i would say try that...before you start replacing unecessary parts.

Title: Re: Over fuelling
Post by: Mboy on 22 March 2007, 21:00

Hi, recieved vag com few days ago but not sure how to work it !! whats the latest software for it ??

Title: Re: Over fuelling
Post by: EvilScotsman on 22 March 2007, 22:54

use the version for your cable or it wont work. 702 beta is the latest but it wrecks copy cables from china etc by wiping the eprom trying to update the firmware.

ver 409 or 607 probably depending on if its a hex usb or hex com.

Title: Re: Over fuelling
Post by: Mboy on 23 March 2007, 09:03

how do i i find out if its a hex usb or a hex com ? all i know is it fits onto the 16 pin port in car using pins 2,4,5,7,10,15, and 16 ? does anyone have procedure on what to follow using vag com ?

Title: Re: Over fuelling
Post by: EvilScotsman on 23 March 2007, 16:48

if its got a 9 pin serial plug on the other end its a vag com, if its a usb on the other end its a vag usb. Theres a manual for download on ross-tech.com and info on what cable works with what program  :cool:

The mk3 only uses 4 pins on the obd as its only obd1 but some very late vr6's are obd2.

Most important stuff works but the system is limited.

Title: Re: Over fuelling
Post by: Mboy on 23 March 2007, 17:32

Cannot start to run vag com because on the port setup i get error message  port status:ok, interface:not found  , any ideas ?

Title: Re: Over fuelling
Post by: EvilScotsman on 25 March 2007, 00:11

is it usb? and what OS are you using?

The drivers have to be installed manually for usb. Instructions are on ross-tech's site