If it fails enough times it will set the check engine light.

The upshift delay valve on the transmission might be going out.

It works off of vacum, so you could have a vacum leak or the hose might be cracked or coming off.

__________________
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".