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Discussion Starter · #1 ·
hi guys strange one this !! so i had on cold start fluctuating revs 800 -1100 then drops off to 400 got the diags on it and came up with a code relating
to hot film mass sensor so i ordered a replacement fitted it and all was fine for a day or so now symtons are back again ! and the only way i can get rid of it
is turning off engine then resarting the car and itd completely fine again.
foto 2 and 5 first start, 1,3,4 after second start.

93ECF7F4-4717-4266-9886-468B204E603B.jpeg
B6877E94-226E-4F23-804B-63ADE4271185.jpeg
E3534C61-7273-4266-8C88-CB0638B0776E.jpeg
045F874A-F9FE-4307-AFC4-AD386924F501.jpeg
5F504F25-7A1B-4F1E-AF8A-E407C0E0B752.jpeg
 

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The engine runs in two states - throttle-body control (when cold) and valve-lift control (after a few tens of seconds). The changeover occurs when the revs drop from 1100 RPM to 700 RPM (A/C ON) or 550 RPM (A/C OFF). Re-starting probably means the engine speed is being controlled by valve lift.

It sounds as if all is OK until valve lift control cuts in from cold. To me it sounds as if the throttle body control is the problem - this is because the throttle body is still being controlled (to set manifold vacuum) even when under valve lift control.

Where the throttle body information comes from to control it will be from the vacuum sensor in the manifold - so, two possibilities: The throttle body is getting stuck, or, the vacuum sensor is not working correctly
 

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Discussion Starter · #3 ·
Hello Timm, i have already check the throttle body its very clean and werking well.
i will check the vacuum sensor next saterday or sunday . I will let you now.
 
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