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.

A: Hello. It sounds like you may have a vacuum...

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!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Battery drain

The smartglow fuses you are referencing won't directly place a noticeable drain on the battery themselves, but if they are blowing repeatedly then there is an electrical short somewhere that could be causing a battery drain on another system. If...

Q: AC not working in car.

It is possible that the refrigerant may be low again or you may have a bad pressure sensor in the AC system. If there is low pressure, or the computer thinks there is low pressure due to a bad sensor...

Q: Shifter locking into neutral

Hi, this problem comes up often. The switch gear may have broken off or has gotten stuck inside. The knob is easily removed by twisting the knob a quarter turn then pulling. If you cannot get the knob off I...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...