2004 Touareg 4.2 V8 - tune out cats?

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Topic: 2004 Touareg 4.2 V8 - tune out cats? (Read 1462 times)

vtraudt

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	2004 Touareg 4.2 V8 - tune out cats? « on: July 15, 2022, 06:35:07 AM »

Car is running fine. Just terrible gas consumption (12 mpg, was 16+ prior).
Codes for bad pre cats and running lean (not sure what gas mileage would be if running FAT ;-)

Debating if I should leave alone and continue to suffer, or if it is worth the effort of taking downpipes down, cut out the pre cats and have cats tune out?

Is there even someone out there who can tune out the cats for that ECU (Nefmoto flash)?

Control Module Part Number: 4D0 907 560 DA HW: 8E0 907 560

16805 - Warm Up Catalyst; Bank 1

P0421 - 001 - Efficiency Below Threshold - MIL ON

16815 - Warm Up Catalyst; Bank 2

P0431 - 001 - Efficiency Below Threshold - MIL ON

17538 - Fuel Trim; Bank 2 (Mult)

P1130 - 001 - System too Lean - MIL ON

17536 - Fuel Trim; Bank 1 (Mult)

P1128 - 001 - System too Lean - MIL ON


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2002 Allroad 2.7T 6spd stage 2
1998 A4 1.8T 5spd stage 3
1996 A4 2.8 auto stock

justinvw2646

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	Re: 2004 Touareg 4.2 V8 - tune out cats? « Reply #1 on: July 15, 2022, 08:15:33 PM »

If you haven’t already take a look at the plastic lines and check valves from the brake vacuum pump that makes its way around the engine bay. They tend to split at the check valves. Could be responsible for the efficiency faults as well. If they are split take them off the check valve electrical tape them to make them round again and push them back over the check valves. They will live a long time like that. Grin


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vtraudt

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	Re: 2004 Touareg 4.2 V8 - tune out cats? « Reply #2 on: July 16, 2022, 03:47:27 AM »

Thanks for the tip. Will try that.
I had once found a cracked hard plastic pipe and fixed as described, but haven't found another (obvious) one. Will chec.
I have a 'smoker' (leak detectio) with a small brass cone for small vac lines, and a larger rubber cone. Any tips how/where to connect the smoker?


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2002 Allroad 2.7T 6spd stage 2
1998 A4 1.8T 5spd stage 3
1996 A4 2.8 auto stock

justinvw2646

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	Re: 2004 Touareg 4.2 V8 - tune out cats? « Reply #3 on: July 16, 2022, 10:26:00 AM »

The plastic lines should be obvious with just a visual. Other intake leaks would be easy enough to find if you have vag com. MVB 33 is essentially instantaneous fuel trims, so use carb clean or something similar while monitoring, if it goes far negative while spraying an area there is a leak. Without sounding like a jerk be careful where you spray so as not to start a fire by hitting the exhaust with a flammable liquid.


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vtraudt

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	Re: 2004 Touareg 4.2 V8 - tune out cats? « Reply #4 on: July 16, 2022, 11:26:43 AM »

Thank you.
Will get MVB33 readings (which of the field is 'instant trim', typically 4 fields shown?)
Starter fluid works even better (for leak detection and setting car on fire!).


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2002 Allroad 2.7T 6spd stage 2
1998 A4 1.8T 5spd stage 3
1996 A4 2.8 auto stock

justinvw2646

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	Re: 2004 Touareg 4.2 V8 - tune out cats? « Reply #5 on: July 16, 2022, 06:19:23 PM »

33.1 is a percentage and 33.2 is O2 voltage. Now keep in mind this is instantaneous from the long term adaptation, so if MVB 32.1 is pegged at either +25% or -25% the info won’t be all that useful so you may have to erase DTC’s to reset long term adaptation (MVB 32). I hope that all makes sense. If you have not erased faults yet see what the values are in 32.1 and 32.2. 32.1 is long term idle adaptation and 32.2 is part load/cruising adaptation (fuel trims). Spec is 0% +-10% but in my experience when things are operating properly its more like +-5%. This way we will know if its and idle problem or off idle problem


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vtraudt

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	Re: 2004 Touareg 4.2 V8 - tune out cats? « Reply #6 on: July 17, 2022, 06:02:25 AM »

Thanks. Had codes erased (and therefore LTFT also reset). No driven since.
Will log/check short term block 33 readings when driving next time.


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2002 Allroad 2.7T 6spd stage 2
1998 A4 1.8T 5spd stage 3
1996 A4 2.8 auto stock

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