A4 1999 failed emisson test and running rough

Honest · 04-27-2012, 10:18 AM

Hi guys,

My car failed emission test and is running really rough, no power in any gears, very diffcult to go up hills.

I am getting the following codes:

00520 - Air Mass / Air Flow Sensor (G70)/(G19)
31-10 - Open or Short to Ground - Intermittent
00523 - Intake Air Temp Sensor (G42)
30-10 - Open or Short to B+ - Intermittent
00537 - Lambda (Oxygen Sensor) Regulation
19-10 - Lower Limit - Intermittent

So far I have changed the CAT and Lambda sensor before the CAT.

I also installed a secondhand MAF a few months ago and changed the plug's about 4 weeks before the problem started.

Please help.

turbo510 · 04-28-2012, 06:36 AM

Have you tried running with the MAF sensor disconnected?

Honest · 04-30-2012, 07:05 AM

Thanks for your help turbo.

I have cleaned the MAF and the first 3 codes have now gone. Car is still running rough and I think it will still fail emission.

I now get this code

00525 - Oxygen (Lambda) Sensor (G39): Signal too Low

Could it be that my new Lamdba sensor is faulty?

This guy has the same problem as me, but no one has posted a solution.

http://forums.vwvortex.com/showthrea...ensor-problems

mime651752 · 05-05-2012, 12:17 PM

have you tested the O2 sensor yet? If its not bouncing below 200mv and above 800mv the sensor could be "lazy"=bad. Also obvious stuff like fouled plugs could cause a rough idle.

Honest · 07-23-2012, 05:59 AM

My Lambda sensor is an aftermarket part from Euro Parts, I have tried two replacement parts from there but still have same problem.

It is defiantly not a bosch, Ngk or Denso part. Can’t remember the name.

Should I buy a genuine one from Audi.

Please help my car has been sat on my drive for months and I do not want to have to scrap my car, if it is just because of Lambda sensor or a minor part.

I have had the car for 7 years now and before the MOT it was very reliable.

4Driver4 · 07-23-2012, 06:52 AM

Clear the codes, drive car, post new codes.

04-28-2012, 06:36 AM	#2
turbo510 AudiWorld Senior Member 2007 Volkswagen Touareg My Garage Join Date: Jun 2008 Location: Yorba Linda CA Posts: 1,443	Have you tried running with the MAF sensor disconnected? __________________ 1996 Audi A4 2.8 1972 Datsun 510

04-30-2012, 07:05 AM	#3
Honest AudiWorld Newcomer Garage is empty, add now Join Date: Jan 2012 Posts: 5	MAF Cleaned Thanks for your help turbo. I have cleaned the MAF and the first 3 codes have now gone. Car is still running rough and I think it will still fail emission. I now get this code 00525 - Oxygen (Lambda) Sensor (G39): Signal too Low Could it be that my new Lamdba sensor is faulty? This guy has the same problem as me, but no one has posted a solution. http://forums.vwvortex.com/showthrea...ensor-problems

07-23-2012, 05:59 AM	#5
Honest AudiWorld Newcomer Garage is empty, add now Join Date: Jan 2012 Posts: 5	Does anyone have any ideas yet for my problem above? My Lambda sensor is an aftermarket part from Euro Parts, I have tried two replacement parts from there but still have same problem. It is defiantly not a bosch, Ngk or Denso part. Can’t remember the name. Should I buy a genuine one from Audi. Please help my car has been sat on my drive for months and I do not want to have to scrap my car, if it is just because of Lambda sensor or a minor part. I have had the car for 7 years now and before the MOT it was very reliable.

07-23-2012, 06:52 AM	#6
4Driver4 Tech Guru Garage is empty, add now Join Date: Oct 2002 Posts: 32,306	Clear the codes, drive car, post new codes. __________________ 4Driver4 "Never give up the throttle until the bitter end." -RC 2005 A6 Sedan Q 3.2 (wife's whip) 2000 A4 Avant Q 2.8 (daily driver) 2003 Mini Cooper S (Fun!) 1995 Mazda Miata: the anti-Audi 1999 Mazda Miata SSB: track beotch 2003 GMC Yukon Denali XL: the anti-earth 2004 Dodge Dakota: hey, at least it's stick and 4x4

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05-05-2012, 12:17 PM	#4
mime651752 AudiWorld Newcomer Garage is empty, add now Join Date: May 2012 Location: Santa Barbara Ca Posts: 4	have you tested the O2 sensor yet? If its not bouncing below 200mv and above 800mv the sensor could be "lazy"=bad. Also obvious stuff like fouled plugs could cause a rough idle.