Fault codes 16804, 17560, 17912

the_IT_bloke

the_IT_bloke

Past Member
Have had the following issues over the last few weeks, each time reset and another fault code appears;

16804 - P0420 Catalyst System: Bank 1: Efficiency Below Threshold
17560 - P1152 Long Term Fuel Trim Additive Air Bank 1: Range 2: System too Lean
17912 - P1504 Intake Air System: Leak Detected

Monitored using VAG-COM at idle with engine warm
Temp 72'C
Lambda hunting from -5.5 to 0
Engine idle 680 - 720 rpm
Ign timing hunting 6-11' TDC
Load 13%
Group 3 load 0.8%?
Group 2 Time 1.02ms
MAF hunting 1.44-1.56 gls
Absolute pressure 270mBar

Any thoughts?
I have looked for air leaks - nothing obvious - nothing perished etc.
No obvious electrical connection problems.
I have read up all the descriptions on Ross / internet - which dont pinpoint to much specifically.

Anyone had any real life experiences? The hunting lambda seems significant.
Is this likely to be the MAF, does it need cleaning?

Any sugestions appreciated.

Thanks in advance
 
Is an absolute pressure reading of 270mbar normal for this engine at idle? i have no idea by the way it just sounds low (i.e. a lot of vacuum if true).

What is it reading with engine not running, I would expect this to equal atmostpheric around 1013 mbar of course depending on your height about sea level..

Gary
 
garywoods said:
Is an absolute pressure reading of 270mbar normal for this engine at idle? i have no idea by the way it just sounds low (i.e. a lot of vacuum if true).

Gary
Click to expand...

It's normal for a petrol car to run a partial vacuum at idle. The throttle butterfly valve virtually closes off the air intake, allowing a lot less air into the engine compared to the ammount the piston wants to draw in on the induction stroke

Cheers Spike
 
I think all these faults indicate an air leak on the intake side - certainly worth having a really good check. Someone once told me that an unlit blow torch round the suspect area will cause the revs to rise as the gas is sucked in. I have never had the guts to try it as sounds a bit hairy!

listen for hissing an get finger in there - but watch for hot / moving bits Ouch!
 
Spike,

Yes i agree with you 100% on the vacuum and the mechanism by which it is created, would be interested though as to whether 270mbar was normal? Just sounds like a lot of vacuum.

Gary
 
Is there any chance some kind soul with diagnostics (and ideally a 1.6FSI engine if it makes a difference) could monitor your Sort Term fuel trim on idle and let me know what the reading looks like???

I understand this would ideally be 0%
After the first minute or two where the management system doesnt read anything, my readings start bouncing continuously around anything from -2 to +8% at idle but I have no idea if this is correct or not. Should the reading sit happily at 0%???

My Long Term Fuel Trim is +21% (Rich) which is obviously what has tripped the Engine Warning Light

Might be a useful set of posts to have some real readings of someones working engines to give and idea of what the readings should be ... anyone interested?? Might help with everyones diagnostics???

Many thanks in advance for any assistance.

Regards

Paul
 
garywoods said:
Spike,

Yes i agree with you 100% on the vacuum and the mechanism by which it is created, would be interested though as to whether 270mbar was normal? Just sounds like a lot of vacuum.

Gary
Click to expand...

Gary
When vacuum gauges were popular for troubleshooting engine problems, 22" Hg was considered a very good reading at idle. As you know 30" hg is a total vacuum so this reading equates to a 73% vacuum. (22/30)
270mbar absolute pressure is the same as a 730mbar (or 73%) vacuum.

The 22" hg figure came from this web site - http://moodle.student.cnwl.ac.uk/moodledata_shared/CDX eTextbook/dswmedia/PDF/ws/vacgauge_WS.pdf


Cheers Spike
 
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Spike,

Yes I agree with your numbers. The 22" in. Hg was the bit i was interested i.e. what is considered a normal vacuum in these engines.

I have read of much lower vacuum values in other engines (albeit older probably more worn engines) which would clearly suggest IT_blokes engine is a good 'un ;-)

I dont have any further input into the troubleshooting by the way, was just curious as to the accepted values.

I think IT_Blokes call for some typical values for certain parameters for engines without issues could be useful in terms of trouble shooting. Unfortunately i have a TDI as you know therefore cant help out in this instance.

Gary
 
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Let me know what channel and measuring blocks you are looking at and i'll pull the data of the mrs's 1.6fsi so you can compare.

cheers
 
bdub
Many thanks for the assistance - sorry for delay in reply
Could really do with understanding;
Group 32 - 1st and 2nd Lambda readings
mine short term -3.5 and long term 21

Group 3 - Mass airflow reading and Ignition timing
At tickover what does the MAF read and what is the BTDC reading - also is it constant or does it hunt?

Any assistance would be appreciated! Thanx
 
ok just plugged up the mrs car here are the results

From start up - group 32 , rpm 960, 1st lambda is -1.5, second is 3.1 but after a minute rpm drops to 760 and lambdas are -1.5 and 2.3.

looking at group 3, MAF is hunting around a bit but generally 3., load shows 3% and timing is hunting between 4.5 and 9.

hope this helps

my readiness shows all passes ie all 11111111 and there are no faults logged.

Shout up if you want any more data for comparision

cheers, Brendan.
 
Mate, that's really kind of you and helpful. My figures are definately out and hunting compared to your.

Logic, your figures and most of the internet says change the MAF.
Only problem is the lack of issues with power, flat spots, hunting idle etc. infers if the MIL had not come on I wouldnt even have noticed....

With my ignition timing hunting wildly I was kinda hoping it would be a timing component / sensor issue but I cant identify anything on the internet to confirm this.

Oh well, loks like its going to be expensive (again).

Can anyone recomend somewhere to buy a cheap MAF? or sugest anything else?

Thanks again for your support!!

Paul
 
Paul,

i did try cheap ( £40) maf from gsf once but only lasted a few months. gnuine bosch ones are def worth it ( £80 ). Could it be related to the lambda sensor as your second reading at 21 long term is massively different to mine?

I think if you unplug the maf the car runns better without a maf than with a knackered one connected - default lookup table in the ecu then kicks in.

might help prove a point.

HTH,
Bren
 
Issue is it could be so many things...:confused:

From my research, if it's a inlet leak the short term trim would be over -3, however it jumps around all over the place. If I rev the engine and let it drop it can settle on +5 then bounce to 0 and all over the place, to +/- 3...

I have read that the high long term trim could be the O2 or the MAF ... too many options.

Its the jumping figures along with the stable idle revs and no loss of power.
I did dissconnect the MAF early on and I 'think' it was the same, but can't remember now, too much research. I may go for the O2 on the exhaust manafold anyway as its cheaper and as likely to be faulty...

Thanks again for support...
 
the_IT_bloke said:
Issue is it could be so many things...:confused:

From my research, if it's a inlet leak the short term trim would be over -3, however it jumps around all over the place. If I rev the engine and let it drop it can settle on +5 then bounce to 0 and all over the place, to +/- 3...

I have read that the high long term trim could be the O2 or the MAF ... too many options.

Its the jumping figures along with the stable idle revs and no loss of power.
I did dissconnect the MAF early on and I 'think' it was the same, but can't remember now, too much research. I may go for the O2 on the exhaust manafold anyway as its cheaper and as likely to be faulty...

Thanks again for support...
Click to expand...

I have had much of the same problems. Only mine says "Long Term Fuel Trim Additive Air Bank 1: Range 1: System too Lean". Yours is "range 2".

I have changed the MAP sensor with no results. However I´m getting a bit confused; Is there a MAF sensor as well? I have 2000 1,4 petrol and was thinking the early models had a MAP, and the later ones MAF. Am I wrong?

Waiting to see how you manage to solve the problem:)

Cheers,

-P-
 
you and me both :) No idea how I will fix it other than with determination :D

No idea on the MAP. I assume that is a Manifold Absolute Pressure sensor, which I guess does the same thing as a Manifold AirFlow sensor but using a very different technique. I would also assume the sensing technology would be much more reliable.

No idea which is installed in what, but I do believe the 1.6Fsi as a MAF, otherwise I am in big trouble :rolleyes:

Keep you posted.

Regards

Paul
 
MAP is usually fitted to turbo engine so the ecu can monitor boost preesure in the intake and adjust turbo according to what the ecu requires. The MAF ( Fitted to 1.6fsi ) measure the mass air flow(this is different to pressure ) to allow correct fuel mixture to be applied.

This is how I understand it, don't think i am far out - sure someone will jump in if it's miles out.
 
bdub said:
MAP is usually fitted to turbo engine so the ecu can monitor boost preesure in the intake and adjust turbo according to what the ecu requires. The MAF ( Fitted to 1.6fsi ) measure the mass air flow(this is different to pressure ) to allow correct fuel mixture to be applied.

This is how I understand it, don't think i am far out - sure someone will jump in if it's miles out.
Click to expand...

Okey, so you either have a MAP or a MAF, but not both...

-P-
 
you could have both, my A4 tdi has both, but i think non turbo cars generally only have a MAF.

cheers
 
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