Skip the auto shop - Our mechanics make house calls

Q: When I start my truck it's idling high and when I'm driving the rpm fluctuate up and down and the transmission doesn't want to

asked by on

My truck seems to be idling high when I'm driving the rpm fluctuate up and the transmission doesn't shift right shifts hard then sometimes want down shift I've changed the throttle position switch and the air intake switch nothing still the same could it be a transmission switch

My car has 170000 miles.
My car has an automatic transmission.

Hello. It sounds like you may have a vacuum leak. This engine is notorious for vacuum leaks from a bad intake manifold gasket. This is very common. It can also be from the MAP sensor or a number of other things. I usually test for vacuum leaks first as I have seen this the most. If you want to have this checked out by a professional, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the high idle and hard shifting so that these issues can be properly addressed.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • When I start my truck it's idling high and when I'm driving the rpm fluctuate up and down and the transmission doesn't want to

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Something is wrong with the passenger's side wheel.

Sounds to me like a loose suspension/steering part or maybe a failed wheel bearing, sometimes a wheel that has come out of balance or a defective tire can cause vibrations or other symptoms that would mimic suspension/steering problems. A certified...

Q: 95 grand Marquis GS

You may have a blower motor with debris that got into it from under dash. It may be paper or other debris that are in the fan blades and will make a rattle slapping noise and can only be cleaned...

Q: Transmission issue after a long drive

Do not change the fluid or have it flushed. This could cause the transmission to go out even sooner. There are a load of different additives out there that may or may not work, but when the transmission is going...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...