MAF readings

Tiny
MANTAS PAULAUSKAS
  • MEMBER
  • 2004 BMW 530D
  • 6 CYL
  • TURBO
  • 2WD
  • MANUAL
  • 100,000 MILES
Hello, I have strange problem, diagnosis will not show any faults related to this problem. I take a look in a Mass air flow LIVE parameter readings and this is what I get:
when engine is cold and below 80 Celsius it works like a charm no vibrations anything, once it reaches 81-95C it start to vibrate on idle till 1000RPM, and then everything is fine.
1) MAF readings below 80 Celsius is same
DESIRED: Steady ~350Mg/Hub and ACTUAL: ~320-355Mg/Hub seems okay and no vibrations.
2) Problem is here: MAF readings when reaches 81-95C it starts to vibrate and MAF readings become's like this:
DESIRED: Fluctuates badly ~300-450Mg/Hub, ACTUAL: 320~430MG/Hub. (MAF IS NEW, and OLD SAME RESULTS)


So my question is maybe a fault DDE ECU? Why DESIRED readings starts to fluctuate it shouldn't do that, it should remain same or just a small increase decrease, but not like that. Who affect's DESIRED MAF readings over 81-95C?
Saturday, March 25th, 2017 AT 12:02 PM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,895 POSTS
Hello,

The MAF is working properly the readings are normal. It sounds like you might have a small vacuum leak, here is a guide to help you find the problem

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please let us know what happens.

Best, Ken
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Tuesday, March 28th, 2017 AT 12:21 PM

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