Car vibrates when at idle and in gear

I recently bought a 2010 Ford Fusion 2.5L 4 cyl, with 145000 miles. When at idle and in gear, the car vibrates, not terrible, but annoying.
When I put in neutral or accelerate, vibration goes away.
When in gear and idle engine is at 500-600 rpm.
When in neutral and idle engine is at 700-800 rpm.
The throttle body was replaced at some unknown point in past. While checking air filter, the filter side of the throttle body looks very clean.
No check engine light.
No other noticeable performance issues (new to me car though).
Any thoughts?

Cleaning the throttle body, along with a computer reset (remove the battery cables for a period) might help if the throttle body bore and flap are visibly dirty with soot/carbon.

Before you disconnect that battery, read this warning.


The visible side of the TB is as clean as new.

I’ve been tricked by this once. The visible side can look clean, but the back side is the dirtiest. Whenever I have a dirty throttle body diagnosis I need to remove the throttle body and clean per manual instructions. You will probably be surprised at what you find behind the throttle plate. I’m not saying the throttle body is the problem, I’m just saying don’t eliminate it from outward appearance.
The symptoms could point to a bad motor mount.

Usually it’s dirtiest beyond the plate. But, it’s not a good idea to manually push open the throttle body on a drive by wire engine. Someone else might chime in on how to clean the throttle body on your particular vehicle. I just removed it on my truck in order to clean it.

Since the car is new to you and there’s no check engine light and if the engine never actually stalls…I guess it’s always possible that the low idle is normal.


1 Like

As far as disconnecting the battery to reset the computer, I wouldn’t be afraid to do it on that car after cleaning the TB, but I suppose it’s not mandatory to do so. The computer will relearn the airflow after cleaning the TB eventually without a reset. Might not be an immediate improvement without a reset.

Thanks. Ill clean the throttle body. When I changed my oil this past weekend, I did look for broken motor mounts. Due to all the plastic in way, I only found one, and I did not see anything wrong with it. Ill look harder on my day off. Thanks!

the mounts look like this…

Is there a good way to actually tell if the mounts are bad? When I looked at the dog bone mount, I looked for cracks. Last time I had a bad mount (years ago), it was obvious. When I gave it gas, the engine would lurch.

Google is my friend… Diagnose and Fix Rough Car Idle - Main Causes For Shaking / Vibrating While at a Stop - YouTube

I doubt that you will see a “broken” mount, you might see torn rubber in the torque mount. The rubber in the engine support mounts gets hard from heat and age and fail to insulate the body from engine vibrations.

Do you know the manufacturer’s spec for the idle rpm? 500 (in D) seems a little low. 800 seems right for neutral. How did you determine the idle rpm, by connecting to the OBD II port? If so, the computer presumably knows what the rpm should be, so then the rough idle would be caused by something else.

  • Electronic throttle control sticking (already mentioned above)
  • Engine Misfire (would usually turn on the CEL)
  • Fuel/air mixture problem (check fuel trims)
  • Too much PVC flow (replace PVC valve, check for air leaks in PVC system)
  • EGR system faulty
  • EVAP system faulty

Note that there could be diagnostic codes stored (possibly as " pending") without a CEL.

Fuel/air mixture problem (check fuel trims)

EGR system faulty
P0401: .
P0404: .

EVAP system faulty

A problem with these systems will also turn on the CEL.


1 Like

good point. I’ll put my reader on it.

not sure on the manufacture spec. I could not find it. I got RPM off the tach on dash.

I couldn’t find the manufacturer’s spec for idle rpm either. Either the data is located somewhere I’m not clever enough to find, or the car’s engineers don’t think measuring idle rpm to try to ID a problem is diagnostic. The rpm displayed on the dash gauge is probably accurate; but sometimes dash gauges (particularly in newer cars) can be misleading, possibly b/c the manufacturer’s don’t want car owners to become overly concerned with what the car’s gauges are displaying.