When the weather becomes warm, more and more BMW drivers are enjoying driving pleasure, offered by BMW. More and more I receive e-mails – there is suspicion, that the engine doesn’t develop max torque/power. What to do in this situation?
In this entry – step-by-step instruction, how to check, if the engine tries to perform in max power.
Check error messages:
a) DME;
b) ABS/DSC;
d) gearbox.
It is self-explanatory, that the error messages in units mentioned before do not allow the engine to perform at full throttle. In case of DME – even as if “innocent and unrelated” error messages as the insufficient efficiency of the catalytic converter, problems with water pump, error messages regarding oil pressure, can have a significant impact on the ability of the engine to develop full torque (max requested torque will be limited by DME).
When all problems are solved and in these units are no more error messages, continue with checking.
2. Open ../F5/F2/F4, switch on the ignition and observe the position of the accelerator pedal. When the pedal is pressed till max:
a) indications of the first sensor has to reach 4.00 .. 4.20 V;
b) indications of the second sensor have to reach 2.00 .. 2.10 V.
In my practice I haven’t seen, that the car has problems with the accelerator pedal – this knot is safe and long-lasting, but if we perform the checking from A to Z, then this anyway should be the first step.
3. Turn on the engine and perform a short driving session. Open ../F5/F2/F1 and, for example, in gear 2, press the accelerator pedal to the end:
a) the opening of the accelerator pedal has to reach 99.6% – this will be a confirmation, that the data of both sensors are interpreted correctly;
b) opening of the throttle has to be 81 oTPS – this will be the confirmation, that there are no obstacles, which could prohibit max torque (by the condition, that the engine works in Homogeneous mode, see the next steps of the check-up).
4. If the throttle is completely opened, open ../F9/F1 and speeding up in gear 2 or gear 3 with the completely pressed accelerator pedal, check following:
a) the engine has to work in Homogeneous mode (Homogeneous mode is a mandatory condition in case of an inquiry for high torque);
b) Lambda values for both banks have to be below 1.00 (they can drop even to 0.90 or 0.85 for a little while).
If the Lambda is below 1.00, it means, that the engine tries to develop max power: injects (till) extra 10.. 15% more fuel as would be necessary for the Stoichiometric mixture (Lambda around 0.90 is a max torque mode).
What could be reasons, if the torque still doesn’t reach required? Simple reason: obviously, the engine has not enough air! Reasons for this problem:
a) air filter. If the air filter is clogged – it has to be replaced;
b) if the engine has DISA valves – obviously there are problems with them.
5. At first in the driving session make sure, that the engine management unit gives directions to open the valves. Start driving, open in INPA ../F6/F1/Shift+F4 and observe PWM values of the valves.
For example, N53B30 O0 engine with two DISA:
a) at 4000 RPM the PWM value of the second valve has to grow to 67%;
b) above 5000 RPM the PWM value of the first valve has to grow to 67%.
6. if it does not happens (DISA valve/s are not directed), typical reason – manual valve management has not been switched back to DME management. To solve this problem:
a) turn on the ignition, the engine OFF;
b) open INPA, ../F6/F1/Shift+F4;
c) pressing F3 and/or Shift+F3, return to management to DME.
7. If the valves are managed, it can be felt, when accelerating swiftly (especially the performance of the large valve – above 5000 RPM). If it can not be felt, that we have to make sure, do the valves are performing at all.
In case of incorrect performance of DISA valves (if there are no error messages regarding them), there could be several reasons for it:
a) mechanical damage. In this case, a check-up with INPA (manual activation) can also not detect the damage, because the turning on of the engine can be heard from the motor room, but the flap itself can be damaged. To perform a complete check of DISA valve, it has to be taken off the inlet manifold and the opening/closing has to be inspected visually, activating it with INPA;
b) have to make sure, that the sealing ring around the valve flap’s frame is not damaged (see the image below, damaged places are marked with red rings). If the sealing ring is not intact, the DISA valve will not perform its functions!
8. If DISA valves are performing correctly, make sure, that the inlet manifold doesn’t have significant oil (or carbon) residues. If necessary – clean the inlet manifold.
9. Check Rail pressure during acceleration. Open: …/F5/F2/F6
Rail pressure should be 200.000 hPa +/5% if RPM > 2000.
10. Reduced efficiency of CO converters. If you have seen following errors: 29F4; 29F5; 2A26; 2A27, make attention to pass/fail counters (description here). If DME determined the reduced efficiency of CO converters, even clearing of these errors will not help. Only when DME will get the confirmation about the acceptable performance of CO converters, full torque will be restored. Take into account – torque will be reduced a pretty long time before a corresponding error is stored into the memory. DME will inspect the efficiency of CO converters for at least several hundreds of km. All this time max torque could be limited waiting for final approvement of correct (renewed) or insufficient efficiency of converters.
11. If the engine has had increased oil consumption, CO catalytic converters can be clogged mechanically (clogging of the NOx catalytic converter has not been observed). Using an endoscope (camera), evaluate the CO catalytic converters, if necessary – they have to be replaced.
12. Turn off ASC/DTC. Press and hold DTC button for 5+ seconds.
