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Airflow sensor issues

Started by Jm4635, 28 June 2024, 04:12 AM


Hey guys,

I have an issue with my air flow plate not opening when I press the accelerator to get it started, this has only happened since I tested all my fuel pressures and put all new vacuum lines in
It's staying hard to press down even with the key out of the ignition,it didn't do this before and the only way to raise the revs is to manually press the flap, otherwise it chokes itself out

Any ideas on where to start checking first ?


Update, I have managed to get the car to idle cold ( which it has never done before) with the air intake propped open with a spanner and the idle adjustment screw fully removed, no ideal I know,
Auxiliary air valve is open but it's like it doesn't get enough airflow through to keep it running when cold,the air valve gets its air supply from the lines going to the top of the motor, but how is it getting air ? And is there another breather I need to check?


First, what car/year?

When you use the linkage to increase engine speed the air flap does not move at all?

I would check all the linkages esp the one that goes down to the throttle body.

Addtionally remove and test your AAV to insure it opens and closes with temp change.  You can put it in a pan of hot water to test.  youtube vids on cleaning.

Why did you test fuel pressure and what were the results?
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'21 E450 Cabrio