lean bank codes, can't find the leak.

petebert · #1 05-20-2019, 02:48 PM

05 x5 3.0i 120k miles. Smoke tested it and found the DISA leaking. Decided to replace the o-ring, found that a previous owner put a Chinese DISA on it. Replaced the o-ring and the codes still came back. Decided to do a better job removing the old gasket material and tried again, codes came back and found smoke leaking from it again. Decided to just replace it with a OE BMW DISA. Codes came back but now I can't find any smoke.

Considering trying a new lower intake hose. Theory I'm going with is that the smoke tester runs at very low PSI but actual driving conditions will draw more pressure and expose a crack in the rubber.

Anything else I can check? If it helps I have the Schwaben scan tool so I could check the readings from individual sensors. Although I'm not sure what values would be in range, say if it's a MAF or o2 sensor issue.

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andrewwynn · #2 05-20-2019, 03:02 PM

I've been fightinf with lean O2 rates codes for a while. It will go away for a while when I reset adaptations but comes back.

I think either my pre cat O2 are sending unhelpful values to the computer or my MAF is sending bad vakues.

Lean also can be from low fuel pressure so it's good to test that to eliminate.

stiubhartach · #3 05-21-2019, 01:25 AM

I had lean condition from low fuel pressure. I finally tracked it down to a split return fuel line inside the tank before the fuel pump check valve.

svvg · #4 05-24-2019, 05:50 AM

I've had this on our E46 325 - same engine (save for capacity....) as the 330i petrol. there's an amazing You Tube guide showing what to change by a guy called the 50sKid - will see if I can find the link.

Anyway. I changed EVERYTHING as the entire car was quite neglected by my GF before we met. Likely culprits - in order - are:

1) Main intake boot - in the pleats/where the smaller side hose attaches

2) DISA (which sounds like it's now sorted - there are various ebay O-rings for sale which you can use if you remove the one you have again (the integrated orange seal needs to be scraped out with a pick first though)

3) Vacuum lines off of the oil separator into the dip stick, and general oil CCV system

4) An easy one to check (which isn't obvious) and which ended up with brown pants moments on the motorway for me - the venturi hose on the brake booster. )The unit is sealed (plastic welded at the factory) - but the lid can separate - it connects the hard pipe from the brake servo/booster to the inlet. The pipe runs across the top of the engine with the wiring harness and fits into the venturi pipe I'm referring to just by the inlet. Worth a visual check.I'd lose servo assisted brakes intermittently - as the lid to the venturi pipe separated and then reseated itself - it fell apart in my hands when I inspected it again.......

https://www.bimmerfest.com/forums/sh...d.php?t=578766

5) check the fuel filter - it has the regulator built in or attached to one end - and the regulator has a vacuum line which is runs in to a very narrow gauge hard pipe. The hard pipe runs from the regulator to the manifold - but it connects via very short and narrow lengths of vacuum line and these perish and can tear. Again a few guides on you tube to replace - but is cheap and easy (just the way I like...)

Best of luck...

svvg · #5 05-24-2019, 05:58 AM

https://www.youtube.com/watch?v=3encrkBsss0

https://www.youtube.com/watch?v=ZDP8Dma0nUs

Second link details replacement of CCV system - and shows all the hoses to replace which might be split... It's a long job but is very easy.

svvg · #6 05-24-2019, 05:59 AM

Part 2 of CCV replacement...

https://www.youtube.com/watch?v=3Mrofw6rRHU

crystalworks · #7 05-24-2019, 10:16 AM

Oil dipstick tube o-ring at the oil pan?

svvg · #8 05-24-2019, 10:29 AM

Quote:

Originally Posted by crystalworks

Oil dipstick tube o-ring at the oil pan?

This is part of the above ccv replacement process - not sure you’d get a lean code - more a massive oil leak - but one of the return hoses from the ccv system feeds into the dipstick tube - and mine was in bits/missing a large section of the hose.

Assume the OP has done a fuel pump/fuel rail pressure test? There's a useful you tube guide on how to look at long term and short term fuel trims to guide you towards lean codes as a result of lack in fuel vs “too much air” from a vaccuum leak. Worth ruling out the fuel pump and pressure reg, as easy to do - and at the clean side of the engine (i.e. From above!).

petebert · #9 05-26-2019, 02:28 AM

No oil leaks, brother is bringing over a fuel pressure gauge and we'll test that tomorrow.

Although has anyone heard of the CEL clearing itself? Mine turned off today. Maybe it needed a few drive cycles? That being said I've been clearing the code myself and it kept coming back. Still going to test the fuel pressure but we'll see if the code comes back.

svvg · #10 05-26-2019, 03:31 AM

Quote:

Originally Posted by petebert

No oil leaks, brother is bringing over a fuel pressure gauge and we'll test that tomorrow.

Although has anyone heard of the CEL clearing itself? Mine turned off today. Maybe it needed a few drive cycles? That being said I've been clearing the code myself and it kept coming back. Still going to test the fuel pressure but we'll see if the code comes back.

Yep. This happened on our 325. I started off by checking fuel pressure which was fine. Then swapped out the ccv system - which was not fine.... but kept getting occasional lean codes with error light which would clear. It turned out to be the sucking jet pump/venturi pipe I mentioned above. The top part of the unit was starting to come away from the main body - when it was sealed the car was fine - but occasionally it would open up - take a quick look as mine fell aprt when I went to inspect it. It’ll take all of 10 seconds to check.

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