Q: Car idles high and then low, and then becomes a 30 second cycle.

asked by on June 09, 2016

My 2008 Dodge Ram 1500 has a 4.7 L engine. When i drive and i stop at a light or i am just at idle, my truck idles around between 750-1000 and after a while idle goes down between 600-750 and it just becomes a 15-30 second cycle. what could cause this?

My car has 130000 miles.
My car has an automatic transmission.

Car idle is rough Inspection $79.99 - $99.99 Get a Quote

Hello. A few things I would check are the throttle body, the idle air control valve, and the vacuum hoses. A dirty throttle body or idle air control valve can cause the idle to fluctuate. I would also examine the condition of all of the vacuum hoses, any cracked or leaking hoses can cause the idle to fluctuate as well. If you need assistance, a certified mobile mechanic from YourMechanic can inspect your vehicle’s idling issues at your home or office.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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


Experienced Mechanic?

Earn up to $65/hr

What others are asking

RPM problems

Hi, thanks for writing in. This may be related to couple of things such as a vacuum leak or potentially an improperly adjusted throttle plate screw. When a vacuum leak is present in an engine, it can cause an imbalance...

My truck cuts out and jerks when lightly applying accelerator at 45 to 60 mph. If I gas on it hard it doesn't do it

It sounds like you may have either a failing throttle position sensor or potentially a dirty or faulty mass air flow sensor, both of which can cause a bit of a jerking reaction when not functioning properly. The mass air...

What would make my car stall with picking up speed?

If the fault codes are reading all 4 coils are bad and the codes remain even after replacing the coils, then the problem is elsewhere. It is very rare to have 4 cols fail at once. There can be an...

I have an 08 lexus rx350, i hear a clunking at low speed on uneven road. I checked the rear wheel by shaking and I feel some free

What you are describing sounds like a failing CV joint. A CV (Constant Velocity) joint is a shaft that connects the transmission to the wheels, essentially transferring the power from the drive train directly to the wheels. The CV joint...

Help!! 2008 Acura RDX

Hi - the "triangle" warning light - by itself - is an indicator that anti-skid braking and traction control are operating. The delay in selecting reverse and poor performance afterward is indicative of other issues. There are technical service bulletins...

Driver's side door hard to close

Hello! On the Dodge Caravans of this particular era, the door pin bushings commonly become out of its designed shape after about 8 years of usage. There are 2 bushings, one on each door pin that act as holsters for...

The back tires keep wearing out, so is it the back struts I have to replace?

If the rear of the vehicle seems unstable going over bumps and the tires have a lumpy wear pattern on them, it is likely the rear shock absorbers have a problem. You should have a technician inspect the function of...

Why does my #1 spark plug continue to burn up in my 2008 Ford F-150

Hello. If you continue to have the spark plug end burn up on just that cylinder then there is an issue with the mixture in that cylinder. It can be caused by a compression problem, carbon build up, or it...

Would leaking exhaust manifold throw a code?

If the exhaust system is not air tight, that will skew oxygen sensor readings and a consequence is a false indication of catalyst efficiency. In addition, the upstream sensor will not be providing a valid reading to the computer insofar...

Related articles

A Buyer’s Guide to the 2012 Dodge Ram
While While Chrysler has decided to give Ram its very own division, it seems impossible not to think of the Ram 1500 as a Dodge. After all, you’ll still buy your 2012 Ram at a Dodge dealer, and it remains...
A Buyer’s Guide to the 2012 Dodge Caliber
If If you’re looking for a compact car that offers a bit more space with acceptable fuel economy, the 2012 Dodge Caliber is a worthy target. The hatchback design is versatile, while the cooling storage compartment, removable flashlight (rechargeable) and...
A Buyer’s Guide to the 2012 Dodge Journey
The The 2012 Dodge Journey is easy to drive, and it’s not so large that you will have a difficult time parking it. It’s an attractive vehicle that has the power you need whether you are hauling a full carpool,...