The upshift delay valve delays the transmission from shifting from 2nd to 3rd gear when the car is cold. It allows the transmission to hold the rpm's higher for about a minute, or until you hit approx 45 mph.

Next time you start the car up in the morning, see if it is working.

If not, it usually caused by the upshift delay valve's inability to hold vacum.

The vacum hose leading to this valve could also either be blocked or cracked.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".