4.2 BFM system too lean only on bank 1
 

Hello from Bulgaria.
As this is my first thread on the forum, please be aware my english is not something to write home about :(
In essence, i`m experiencing the following problem: a couple of days ago the chack engine light came on and as i took a look at it using vcds i pulled out the system too lean code but only on bank 1. I did delete the code and thus reset the fuel trims and went for a drive. Surprisingly, observing channel 33 i noticed that the car was running lean but only on bank 1 - adaptation values started reached 13,7% which is a real problem.
What was done on the car befor the MIL went on - both chain tensioners and chains changed with OEM, channel 93 show 0 and + 1 kw :)
New OEM MAF, new coils from BREMI, new spark plugs from NGK, vacuum leaks tested with smoke machine - no leaks, new PCV valve from VAICO, timing belt kit and water pump were also done, new air and fuel filter, new "main" fuel pump - fuel pressure is ok.
After i pulled out the code i checked the system again using smoke machine with no result. i got another new MAF from Bosch.
Car runs fine, fuel consumption is ok.
Important to mention is that i got the SAI system deleted from the ECU. Afterwards, working on the suspension, i removed physically the secondary air pump and sealed the hose that goes into the intake manifold. After a few cold starts i noticed the engine was running rough when started cold so it flashed upon me that no extra air goes into the intake manifold as the air pump was not there but the combi valves (also called egr valves) were still working thanks to the seconday air inlet valve. One can guess what i did - i sealed the vacuum line that goes into the valve without disconnecting it and whoa - engine runs fine when cold now.
To the problem - the lean condition on bank 1 appear only on partial throttle - shall i push the gas pedal to the floor and drive a couple of miles, the long trim fuel trim adaptation goes to 2% which, in my opinion, is perfect.
As to the vacuum leaks - i not only tested the car with a smoke machine but also pored gallons of break cleaner in the engine bay looking for a vacuum leak - as the most of you know, there are non - return valves in the vacuum lines that operate and open after certain rpms. I can positively say vacuum leaks are to be ruled out.
What i`m planning to do is to check the fuel injector for leaks.
I forgot to mention - the car runs on LPG and has a BRC LPG system installed. Bank 1 runs lean on load on both gasoline and LPG, which makes me think it not the gasoline injectors as well.
Another thing to be checked is the evap canister. Fuel tank has no vacuum when open , the cap looks ok, is not new but OEM. AS the car runs i can hear the evap valve ticking which makes me thing it works fine.
Any suggestions on what i`m missing and what shall i check? Thank you in advance and hope you understand my English.

Hi Josepe,
Though I cannot help with your engine problem, I have a 3.0 TDI, I must congratulate on your English. It is mch beter than mine and I have lived all my life in England.
Welcome to the forum.
No doubt one of our more knowledgeable members will be along shortly to help you.

This could very well be the LPG software mapping needing a tweak by an LPG specialist. LPG systems are supposed to "Learn" and adjust themselves to their final behaviour / settings but sometimes it needs the software / LPG map to be adjusted for some cars, so I would look at this first, preferably with the LPG company who fitted the system. Mine took 2 visits to get it right

Architex ........ he does say its lean running on both gas and petrol so maybe a more common fault here .??


Josepe

Some good diagnostic fault finding going on here .....you have covered most of the things i would of asked with this fault, even smoked it... very good


So to just confirm some things

At idle are short term and long term fuel trims near the 0 value ( after clearing code and doing reset )

The vcds block 93 being near 0 or 1 kw (degrees of rotation ) is that both banks of cylinders left and right at those values .

If you drive at a steady speed and watch the before cat lamdas on both banks is the lamda equivalence ratio going to a lean value on the faulting bank .... lamda 1 or higher 1.100 or above and so on , also look at the after cat lamdas is one of them going to a leaner reading ....good reading around 0.7 volts ....leaner will be below 0.7 ....at steady throttle the after cat lamdas should be pretty constant .
Very ofen after cat lamdas have some bearing on fuel trim calculations ...so if one bank has a bit of a bad cat it could affect fueling ( normally get codes for poor cats ...but never assume !!)


The inlet manifold .....these have the variable length tracs ...are all the linkages to each shut off flap working and connected to the operating arm , im thinking at the areas you are going lean one bank could be at one setting and the othe bank at another .

Before the car had all these timing chains repaced was this code for lean mixture present ?
Could you do put a vaccum guage on inlet manifold and look at the reading , ive found good engines pull around 20 inches of mercury or around 350 millibar.

If im correct on this engine the cam sensors are only on inlet cams so the exhuast cams could be off and you would not know this , it would perhaps make it run a bit rough at idle .....the vaccum test is good for showing cams being off .
A few things to have a look at .

"I have a 3.0 TDI, I must congratulate on your English. It is much beter than mine and I have lived all my life in England."



Most folks English is better than Wigan English Ray ....... areet cocker .....am clempt deethh ......++++++

a little update - went for a ride and made these logs:

Yes I read what he said Lee, but having had exactly this issue on mine, getting the LPG tuning/mapping re-sorted finally cured it and I don't get the issue any more, so it's a valid possibility. Also he doesn't say if it occurred solely when running only on petrol or if he meant that the car runs on both, which most Lpg cars do as they start on petrol until warm then switch over. If he's never had the Lpg system looked over or checked since getting the car then it's probably relatively low cost to do so and might cure things. . .

" Bank 1 runs lean on load on both gasoline and LPG, which makes me think it not the gasoline injectors as well."

I took that as running lean on both gas and petrol ...maybe im wrong


So on yours it would pull up codes for lean mixture just running on petrol ....but tweaking the gas mapping sorted the petrol issue as well

If youve got LPG then you dont really run it on petrol unless you are forced to at 50p per litre versus £1.25! But in my case the LPG tweaks sorted the issue and when i ran it around ireland last summer there was a couple of sections where I had to run it on petrol and the issue has never to my knowledge cropped up on petrol at all. Seemed to be to do with doing long journeys then suddenly doing a lot of town driving and the map not adjusting itself correctly to both

Joseph

Does the car show lean fault codes when it is running on petrol ?

Or is it when it is just running on gas ?