Skip the auto shop - Our mechanics make house calls

Q: Truck idles rough

asked by on

Hello. I changed the spark plugs, wires, fuel filter and removed the cat converter off my truck. Its still idles a little rough like it has a miss but while driving it its ok. Any idea what it could be? Also when starting it it normally takes a second turn for it to turn over.

My car has 150000 miles.
My car has a manual transmission.

This is a sign of a failing idle air control valve. This is a unit that is located on or near your intake manifold that monitors the air intake as it is mixed with fuel prior to being injected into the engine. This valve is controlled by the vehicle’s computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is nearing its replacement age, your vehicle will stall instead of idling after the release of the throttle. I would recommend having an expert from YourMechanic come to your home or office to confirm a diagnosis on the rough idling issue and make or suggest the necessary repairs or replacements.

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・Fair and transparent pricing

Get a quote

What others are asking

Q: What should I know about the positive retention floor mats?

Your floor mats provide protection for the carpeting under your feet, and the mats used in your vehicle have a special design. They’re what are called positive retention floor mats. They use a hook system to keep them in place...

Q: Acceleration problems, car shaking and check engine light on

Hi there. There are a few different things that can cause this. It can be the fact that the speedometer is not working due to a bad transmission speed sensor. This can cause the computer to not know when to...

Q: Radiator leaking badly

The radiator connects to the engine via a radiator hose. There are actually two hoses, a top and bottom hose. The top hose is the one that is usually easier to see. The hose connects the radiator to the thermostat...

Related articles

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...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...