I have a 2002 Cadillac Deville with 90,000 miles. A few months ago, the code for TCC Solenoid popped up. My MPGs dropped from 26mpg - 22mpg highway, RPMs rose around 200 rpm at 65mph. Acceleration from road speed (around 35mph) to highway speed (65mph) does not downshift and sucks gas big-time.

The lowest estimate for repair is 11 hours and $715 ($60/hr + $55 TCCS mobile mechanic in ORLANDO FL). Others have a LOT higher labor rates. I can not afford to get it fixed yet (probably several months), and I do not have the ability to do it myself (unemployed). My two questions are:

• Is there any harm in waiting?
• Could I drive in 3rd (not OD) until I get to highway speed, shifting then to OD, and will that help MPGs and acceleration?

TS

 

Running with no Lock-up will kill your fuel mileage, as you have found. If you drive long enough(on the road) with no lock-up, the trans fluid will overheat, and create new problems. If most of your driving is in town, it won't be as much of a problem.
Shifting manually as you ask won't really do much good, so that won't really make any difference.
What specific code are you getting? There are several that pertain to a lock-up issue, but in the end, the usual suspect is NOT the solenoid itself, tho it is usually melted. Replacing the solenoid may get you by for a little while, but it is not the real "fix". The "fix" is removing the transmission and disassembling it. Then the two seals that are leaking can be replaced, along with the torque converter and TCC solenoid.
It's rare that the TCC solenoid by itself fails....it normally fails due to converter slippage, which in turn is caused by the leaking seals.