Bmw 535 B2 Lean
Hi All, Customer dropped off his 2010 535i with lean bank 2 code stored. fuel trim for bank 2 is around 20% at idle. bank 1 is in single digits. This car has already been to other shops to be fixed. so far the other shop has replaced the valve cover, did a valve cleaning, new fuel pump and fuel pump module, new spark plugs, new upstream o2 sensors. We ran a smoke test and replaced the intake pipe to throttle body because it was leaking, no change, no other intake or exhaust leaks could be found, I did spray intake cleaner all over the intake to check for a change in fuel trims to verify no intake leaks. I replaced the bank 2 o2 sensor again just to be sure there was not a faulty sensor installed previously. the bank 2 injectors were updated (index code 11) on all 3, the bank 1 injectors are probably original (index #9). all of the injector flow rates are programmed in the ecm correctly, I even programmed them in again to be sure. Im running out of thought on this one! Wondering if possibly the downstream o2 sensor can have an effect on fuel trims on this vehicle.
Gerald, yes the downstream could effect fuel trims. Have you used Generic data and looked at the o2s for that bank? also does the lean STFT decrease as you raise rpm during power braking and how do the o2s responded? you could also reset fuel adaptations, NOT CODES, graph your STFT and o2s while you let it run after the reset. watch the count of the fuel trims and see what the o2s do.
I reset adaptation already and it runs very bad until the computer adapts to whatever is wrong.. the trims get slightly better under accel but are still elevated only on bank 2
Check the turbo charger bypass valves - parts number … and … - Check the vacuum supply to the valves and compare their operation. Check the vacuum supply and control for the turbos. If one of the turbos’ deviates in its operation from the other there will be problems with the trims of one of the banks
Your problem is only on one bank, I feel and you know too much work has been done chasing this problem, they can be tough. Always consider propane enrichment tests when looking at these kinds of fuel trim issues to verify o2 sensor operation and response time and also use oxygen only from your torches to see how it responds to lean conditions, compare the sensor response to the other sensors…
Also worth mentioning I have seen many times where a lean code sets on 1 bank only to find out that the other bank is very close to failing and it was a maf sensor issue, also like to run the engine at a high rpm in 2nd or 3rd gear to see if fuel trim is in control there to eliminate fuel pressure and volume issues.
I agree with robert about only coding for one bank but both are lean…can you test crankcase vacuum?if it runs poorly when adaptions are cleared I doubt its o2 readings(unless it runs poorly when it closes loop) what are the actual trims at idle and cruise?new valve cover brand??
There is one place vacuum can leak that often gets overlooked. There is a line going to the exhaust flap in the rear. The downstream o2 DOES have an effect on fuel trim. ISTA actually tells you to replace both if you have a problem with one.
You did not mention codes for misfire but with 20%+ for fuel trims on bank 2 there may be a misfiring cylinder there. If a cylinder in bank two misfires the trims will be lean. I think bmw calls it cylinder smooth running values - check them and see if one cylinder is worst than others. You write the car runs very rough after reseting adaptations. I would reset adaptations when the engine is…
Gerald do You have a scan tool with graphing capability, that you can graph short term and long term for both banks on the same screen on a short test drive uNader different loads.
It’s very lean at idle, it’s only slightly elevated under load
so even the smallest little thing at idle is a much larger percentage of what is happening and enough to set a code, by now you have ruled out a biased rear sensor stuck low…and there is no vacuum leaks??? You checked the intake and crankcase with a flow meter, BMW has a pid to adjust idle speed, you cleared the codes, reset the adaptation and the code comes back from extended idle, did you…
On the N54 I have seen the valve cover cracked in the middle , I cannot recall the symptoms it produced, but make sure your plastic valve cover is t cracked
If this is a map car and not a maf car obviously it has no vacuum leaking at idle because it would be rich!!
OK, So this thing DOES have an exhaust leak above the rear 3 cylinders that I can smell and it will burn your eyes if you put your head down right above the manifold. But I cannot see or hear anything. has anyone seen common place that these leak from? I'm going to tear it down but just wondering if theres any very common things that develop leaks.
So it’s sucking air on deceleration, false air, o2 sensor thinks it is lean, good find, high volume high press smoke test of the exhaust, not many have that, great find sticking with it, one more bit of experience in your arsenal, be well, Bob
It’s absolutely the bank 2 turbo, i can hear the exhaust leak flutter if I move the wastegate lever around and the lever has a ton of play. The bushing is very bad. Customer approved the repair to replace both turbos.
VW Audi Has a waste gate sealing issue as well, we see a lot of it.