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'96 Buick Century-high idle, no speed increase

My brother recently decided to clean off my engine with a high pressure water hose at our local car wash (with the help of a degreaser). Since then I have an erratic idle. I brought car to auto dude and he suspected maybe a sensor got wet and just did a transmission flush and filter change. The car was fine when he test drove. However, when I left the repair shop and got the speed up to 50mpr it just continued to rev really high with no speed increase or gear change. I stopped at a light (no high idle) then hit the gas, got up to 20, 30 mph and no gear changes and could not get past 30mph. Just revved really high. Service Engine Soon light has been on the whole time. Bottom line, the car is back with the repair guy and he is sorta dumbfounded. Hooked up to computer and hasn’t been able to pinpoint problem yet.

Any suggestions??

One thing to check is if the throttle position sensor got wet and is now sending a false signal to the computer. The signals from the TPS to the computer control engine speed and shift points of the transmission.

Tester

After it dries, would the problem still exist?

I appreciate any and all replies in advance. Thanks!

Try unplugging the connector from the TPS to make sure water didn’t get forced past the connector seal. If water is found in the connector, spray the connector with WD40.

Tester