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D3 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again

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  #1  
Old 5th April 2018, 12:21 PM
ulfilias ulfilias is offline
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Default MOT Fail - Emissions - Probably Cats

Hi There,

4.2 V8 Petrol ~162,000M


Just had an MOT.....Failed Emissions on CO on Idle, 2nd fast Idle, Fast idle and HC/Lamda on the fast Idle.

The Co points to the cats. I've had the Check Engine lights on for quite a while on both banks which I thought was odd (16814 & 16804)....I did try a few cleaners when I got the car, but since it's passed the two years previous MOTs I haven't been worried.

I've got some toluene so I may give that a go and see if it gets better, but I'm guessing it's a pair of new cats ???




Any help, pointers etc

Lee
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Current :
2005 A8 Sport 4.2 V8 D3 - LPG mostly working!

Previous :
1998 S8 PF 4.2 V8 D2 - Gearbox died ~120k
2002 S8 FL 4.2 40v V8 D2 Prins LPG - Engine valves met pistons ~230K

Also :
1996 Jeep Grand Cherokee 4.0l (not worth selling!)
2003 Brabus Smart FourTwo (for sale)
2003 Mazda Rx8 2.3 (should sell)

Last edited by ulfilias; 5th April 2018 at 12:26 PM.
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  #2  
Old 5th April 2018, 01:16 PM
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snapdragon snapdragon is offline
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If the lambda probes are not too expensive I would just replace those as it failed on fast idle lambda value / mixture.
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Old 5th April 2018, 02:34 PM
ulfilias ulfilias is offline
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Just had a play with VCDS

I'd cleared the error code before the MOT, but i just did a readiness test and it passed everything apart from the Cats, so 0000 0001

It seemed to think the sensors with the aging test was ok

Blocks 46 and 47 read Cat 0.13 and 0.19

I've got some Toluene and half a tank of gas, so i'll go for a drive and see if I get any real change.

I had a cat issue with an Rx8 I have and on swapping, found the housing empty....Am wondering with an inspection camera if you could feed it down the exhaust or maybe break the pipe and do a visual inspection???
__________________
Current :
2005 A8 Sport 4.2 V8 D3 - LPG mostly working!

Previous :
1998 S8 PF 4.2 V8 D2 - Gearbox died ~120k
2002 S8 FL 4.2 40v V8 D2 Prins LPG - Engine valves met pistons ~230K

Also :
1996 Jeep Grand Cherokee 4.0l (not worth selling!)
2003 Brabus Smart FourTwo (for sale)
2003 Mazda Rx8 2.3 (should sell)
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Old 5th April 2018, 02:40 PM
ainarssems ainarssems is offline
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I agree as it failed lambda as well it's more likely to be first lambda sensors or possibly air leak. Have a look at values for lambda voltage in measuring blocks with VCDS. They should be changing quite sharply between approximately 0.2-0.7V about once per second. If there is no activity, smaller range or slow to respond then it/they are faulty. But if you keep driving with faulty lambdas for long time that will eventually damage cats.
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Last edited by ainarssems; 5th April 2018 at 03:11 PM.
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Old 10th April 2018, 04:23 PM
ulfilias ulfilias is offline
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Looking at the MOT they'd tested it on Petrol. Retest on LPG and that's the MOT sorted.
However the LPG runs rough and having been through the system, plugs and coil packs, I have a feeling the sensors may be having an effect there, so i'm going to have to do some investigation there, but at least it's not the CATs. Workshop guide for the garage was say 12.5hrs for a cat and 13hrs for them both!!!
__________________
Current :
2005 A8 Sport 4.2 V8 D3 - LPG mostly working!

Previous :
1998 S8 PF 4.2 V8 D2 - Gearbox died ~120k
2002 S8 FL 4.2 40v V8 D2 Prins LPG - Engine valves met pistons ~230K

Also :
1996 Jeep Grand Cherokee 4.0l (not worth selling!)
2003 Brabus Smart FourTwo (for sale)
2003 Mazda Rx8 2.3 (should sell)
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Old 10th April 2018, 08:49 PM
Mechcanico Lee Mechcanico Lee is offline
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Can you post all gas readings off print out

Are pre cat Lamdas 5 wire wide band ?

What is short term fuel trim doing at idle and at say 2500 rpms
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Old 11th April 2018, 01:10 PM
ulfilias ulfilias is offline
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Mechcanico Lee

Bit confused on what you want, but happy to play!

I can hook up VCDS this afternoon and look the fuel trims, LPG or Petrol?

CO is fine on LPG, though HC is high, but just within the *MUCH* wider limits than on petrol and only until the LPG drops cylinder 8 though it also mentions 10??? It's only a V8

I think what is happening is that the post cat sensors being out is meaning that it's either under or over fueling causing the emissions issues and the LPG is trying to trim to such an extent the miss fires are happening!
__________________
Current :
2005 A8 Sport 4.2 V8 D3 - LPG mostly working!

Previous :
1998 S8 PF 4.2 V8 D2 - Gearbox died ~120k
2002 S8 FL 4.2 40v V8 D2 Prins LPG - Engine valves met pistons ~230K

Also :
1996 Jeep Grand Cherokee 4.0l (not worth selling!)
2003 Brabus Smart FourTwo (for sale)
2003 Mazda Rx8 2.3 (should sell)
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Old 11th April 2018, 01:39 PM
ainarssems ainarssems is offline
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Post cat lambdas is only there to monitor cats, they do not affect fuelling.
All lambdas are narrow band on D2.
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  #9  
Old 11th April 2018, 02:41 PM
ulfilias ulfilias is offline
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ainarssems - It's a D3!
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Current :
2005 A8 Sport 4.2 V8 D3 - LPG mostly working!

Previous :
1998 S8 PF 4.2 V8 D2 - Gearbox died ~120k
2002 S8 FL 4.2 40v V8 D2 Prins LPG - Engine valves met pistons ~230K

Also :
1996 Jeep Grand Cherokee 4.0l (not worth selling!)
2003 Brabus Smart FourTwo (for sale)
2003 Mazda Rx8 2.3 (should sell)
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  #10  
Old 11th April 2018, 04:42 PM
ulfilias ulfilias is offline
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Hi There,

Just had a play with VCDS.

I ran the Readiness check (http://www.ross-tech.com/vcds/tour/readiness.php) Which checks various engine bits. The other day it passed all but the cats. Today it passed everything when going through, but the Evap showed fail too!
This checks the secondary air (vac??) and a few other bits. It seems to think the lamda sensor aging is fine though?

I cleared the engine faults so it clears the trims on block 032.

I ran it for a while checking through all the engine blocks and then checked again and ran 2520rpm

Block 01 - 2520rpm, temp 99c, Lamda1 -3.9%, Lamda2 2.3%
Block 02 - 2520rpm, Load 15%, Inj Time 2.46ms, MAF 18.36%

Block 032 -Idle (+) Partial (X) - B1 - Idle (+) Partial (X) - B2
1.3% -1.6% 0.4% -0.8%


I then thought i'd give the LPG a go and see what that did

Block 01 - 1120rpm, temp 102c, Lamda1 -18.8%, Lamda2 0%
Block 02 - 1120rpm, Load 15%, Inj Time 2.87ms, MAF 7.68%

Block 032 -Idle (+) Partial (X) - B1 - Idle (+) Partial (X) - B2
1.3% -18.8% 0.4% -0.8%

Also got

16684 Random Misfire P0300
16692 - Cylinder 8 P0308Misfire
17718 - Cyl 10 Ignition circuit - P1310 short to ground
17536 - P1128 System too lean


BTW - I got the 5/8 coils swapped by audi under warranty, I then swapped the last 3 so it had new coils. I've also tried two complete set of spark plugs.

I took it to an LPG guy and he played and swapped LPG injectors - I do also have the Zenit LPG software and can do some things in there, however the conclusion of the process that it seemed to be the car shutting things down and I just never got it to the point it would do anything but the above style faults. IIRC the cylinder that shuts down varies too!
__________________
Current :
2005 A8 Sport 4.2 V8 D3 - LPG mostly working!

Previous :
1998 S8 PF 4.2 V8 D2 - Gearbox died ~120k
2002 S8 FL 4.2 40v V8 D2 Prins LPG - Engine valves met pistons ~230K

Also :
1996 Jeep Grand Cherokee 4.0l (not worth selling!)
2003 Brabus Smart FourTwo (for sale)
2003 Mazda Rx8 2.3 (should sell)
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