Fuel economy falling- solved

[carrots 1]

try unipart additives there a lot cheaper than wurth

[Pat_McCrotch 0]

try unipart additives there a lot cheaper than wurth

 

And for a reason too! :)

[4eyes2wheels 0]

Scanned with VAG COM and I find

 

VCDS-Lite Version: Release 1.1

Thursday, 01 September 2011, 20:49:13.

 

Chassis Type: 50 - VW Corrado

Scan: 01,02,03,15,25

 

-------------------------------------------------------------------------------

Address 01: Engine Labels: 021-906-258.LBL

Controller: 021 906 258 AG

Component: MOTOR PMC 1

Coding: 0261203109

Shop #: 1267357531

VCID: 59C50E67D017

3 Faults Found:

00525 - Oxygen (Lambda) Sensor (G39)

29-10 - Short to Ground - Intermittent

00537 - Shareware Version. To Decode all DTCs

08-00 - Please Register/Activate

00553 - Shareware Version. To Decode all DTCs

29-10 - Please Register/Activate - Intermittent

Readiness: N/A

-------------------------------------------------------------------------------

Address 03: ABS Brakes Labels: 021-906-258.LBL

Controller: 1H0 907 379 C

VCID: 2F1190BFFE13

Note: Excessive Comm Errors

 

So looks like the Lambda Sensor is suspect. 00537 also a lambda code I think but 00553 is MAF perhaps?

 

Is it the sort of thing an idiot (like me) can unplug and replace?

Edited September 1, 2011 by 4eyes2wheels

[davidwort 0]

Follow the lambda wiring back from the sensor to make sure there's no damage, but yes they just unscrew and plug in, access can be a pita though and old sensors can be tight in the exhaust/cat. You can cut the old lambda wiring to get a socket or ring spanner on, but you might struggle getting leverage especially if the car is just on axle stands.

[swiftkid 1]

I've seen this quite a few times, mine has done it in fact. Basically the MAF fails, sends the fuel a bit crazy, lambda then picks up the fault and struggles to control the fuelling so pops up a fault code making you think its the lambda at fault.

There are loads of threads about checking the MAF, might be worth getting the engine up to temp, unplugging the MAF and see if the engine starts to stutter. If there is no difference I would say MAF in which case firstly I would try resetting the ECU, running it for another week or 2, if no change replace the MAF.

 

A little trick I picked up on vcds-lite is that if you go to full scan you can't clear error codes, but if you go into each individual module you can :thumbleft:

[4eyes2wheels 0]

I've seen this quite a few times, mine has done it in fact. Basically the MAF fails, sends the fuel a bit crazy, lambda then picks up the fault and struggles to control the fuelling so pops up a fault code making you think its the lambda at fault.

There are loads of threads about checking the MAF, might be worth getting the engine up to temp, unplugging the MAF and see if the engine starts to stutter. If there is no difference I would say MAF in which case firstly I would try resetting the ECU, running it for another week or 2, if no change replace the MAF.

 

A little trick I picked up on vcds-lite is that if you go to full scan you can't clear error codes, but if you go into each individual module you can :thumbleft:

 

Thanks swiftkid - it's running pretty rough at the moment. Will have a go over the weekend. Good tip on the VCDS-LITE.

 

"Resetting the ECU" - what does that entail? I have a DG map but assume it's just a sort of reboot rather than a reset to factory default rest?

[swiftkid 1]

Yea, check the wiki guide but it basically makes the ECU forget all its lambda learn't values and obviously if your maf isn't working it will force it to try use it again, so might be worth cleaning it first (with electrical cleaner but be careful!).

 

Before you do go resetting anything just unplug your MAF and see if it starts to struggle, if it just changes tone a slight bit then goes back to normal chances are its MAF playing silly buggers. If you have the later type MAF you can easily get hold of a cheap replacement, I bought one for £6 off ebay the other day.

[RW1 0]

"Resetting the ECU" - what does that entail?

Post up your Engine ECU group 6 field readings (4 readings). You may not need to reset if the readings are resaonable. Just Basic Settings on the throttle may suffice after you have fixed the Lambda/MAF.

 

.

[4eyes2wheels 0]

might be worth getting the engine up to temp, unplugging the MAF and see if the engine starts to stutter. If there is no difference I would say MAF in which case firstly I would try resetting the ECU

 

Got up to temperature this morning then parked up and unplugged the connector to the MAF and the engine carried on running the same - just a slight change in engine note when plugging in / unplugging.

[Pat_McCrotch 0]

You'll definately have an earlier MAF on a 1993 car. Now obselete at VW but Euro Car Parts still do the Bosch one for £125.

 

If it's never been changed in the 17 years on the road I would get one anyway. My car felt flat and stalled occasionally when coming to junctions. When I changed the MAF car felt more alive and IIRC fuel consumption did increase slightly.

 

It's a weigh up of cost vs hassle. MAF is £125 and a doddle to change (and could probably do with a change anyway). A £125 or so Lambda in a 17 year old catalyst will ideally need a ramp and allot of swearing.

Edited September 3, 2011 by Pat_McCrotch

[buttles 0]

If it had been an 'Adaptation limit exceeded code on the Lambda then I would go for another cause but a short to ground does point towards a wireing problem in the Lambda circuit. Worth fully checking before spending money. I have a lambda socket here if need be

[4eyes2wheels 0]

You'll definately have an earlier MAF on a 1993 car. Now obselete at VW but Euro Car Parts still do the Bosch one for £125.

 

As my existing one looks like it's been there ages I have just ordered one of these http://www.eurocarparts.com/ecp/c/Volkswagen_Corrado_2.9_1993/p/car-parts/engine-parts/fuel-and-engine-management/engine-management-sensor/?434440481&1&ab85357232d8374c54fe55678ed46cac043da194&000009 . £80 with discount code PCP25 !!

---------- Post added at 10:54 AM ---------- Previous post was at 10:53 AM ----------

 

If it had been an 'Adaptation limit exceeded code on the Lambda then I would go for another cause but a short to ground does point towards a wireing problem in the Lambda circuit. Worth fully checking before spending money. I have a lambda socket here if need be

 

I will bear this offer in mind - thanks!

Edited September 5, 2011 by 4eyes2wheels

[4eyes2wheels 0]

Cleared the codes at the weekend.

Went for a spin round the block (half a mile)

Rescan - no codes. Guess it takes a while for them to register

------------------------------------------------------------

Wednesday night

Fit new MAF (hooray perhaps I CAN make a career as a mechanic?)

And the car actually runs after I've finished.

Ran the engine for a few mins - couldn't be bothered to move the cars around as it's been a hell of a day at work - grabbed the cables and did a quick scan.

Now I'm getting

533 and 513 - Idle speed regulation (intermittent) and Engine speed sensor.

 

Am I right in saying I actually need to take it for a decent run to generate the codes for any real faults?

Edited September 8, 2011 by 4eyes2wheels

[buttles 0]

I find Lambda codes come and go at their leisure. Leave it for a few days and scan again. Idle speed regulation may have been triggered by unplugging the MAF when engine running. Assume the engine speed sensor code came up with engine stopped so ignore.

[4eyes2wheels 0]

I find Lambda codes come and go at their leisure. Leave it for a few days and scan again. Idle speed regulation may have been triggered by unplugging the MAF when engine running. Assume the engine speed sensor code came up with engine stopped so ignore.

 

Cheers! I work in London so car tends to only get driven at weekends. I'll go for a decent spin and see how things shake down.

[4eyes2wheels 0]

Just back from Tuning Werkes in Croydon. They tested the lambda probe and basically it was a cheap piece of cr4p that has been replaced with a proper one and all sorted. Fuel economy is up. So in the last two weeks the VR6 has had a MAF, Lambda sensor AND a new Jetex exhaust.

[budhilton 10]

Good to see you sorted your problem. Is it still ok ? Is changing the MAF a plug and play type swap over or more complicated ? Mine is a 95 2L 16v and I am getting 22 mpg

 

Andy

[dr_mat 0]

I gained 3-5 mpg over the whole range when I replaced my MAF sensor about three years ago. And there was nothing really wrong with the old one, the car ran absolutely fine.

[4eyes2wheels 0]

I am a complete numbskull mechanically but I was able to swap the MAF over in 10 mins. undo a couple of jubilee clips and remove old one, replace, re-tighten jubilee clips. Job done.

 

My economy is in the low 30s now, but I have also had a new lambda sensor which should have helped too!

[Kevin Bacon 5]

Just back from Tuning Werkes in Croydon. They tested the lambda probe and basically it was a cheap piece of cr4p that has been replaced with a proper one and all sorted.

 

Yep. The VW ECU will have been 'harmonised' to a particular lambda probe, so a cheap pattern won't work as well.