Rough Idling

I have a 2006 Dodge Stratus with approximately 104,000 miles on it (most highway) and I’m at my wit’s end trying to figure out my rough idling situation. When I was at stop light, I would notice a rougher than normal idling but not to the point where stalling would occur. The timing belt was just replaced a year and a half ago and I thought maybe something was wrong with the alternator??? I took it into the shop and they replaced my engine mounts, replaced spark plugs, and did a fuel injector cleaning…nice huh? Well not exactly…now the idling is 10x worse to where my entire steering wheel is shaking when I’m stopped at a stop light! The car itself just sounds rough.

No check engine light is on and the idling isn’t nearly as bad as when I park the car…a part of me wants to throw in the towel and say it is what it is, but I just have a feeling that something’s just not right. Any feedback would be appreciated!!

independent shop or dealer?

Is/was your Check Engine Light illuminated? Did/do you have any fault codes? Did the shop scan the ECU for stored codes?
Any other symptoms?

There are a number of possibilities including but not limited to a
carboned-up EGR valve
bad coil
bad injector
carboned up or burned or otherwise malfunctioning valve (I’m thinkin’ valve train)
bad motor mount
bad IAC
low compression in one cylinder would have been an initial guess, but since it got worse after it was worked on I’m inclined to look elsewhere first…but it’s still a possibility.

The next time the rough idle occurs, place your left foot firmly on the brake pedal and with your right foot slightly step on the gas pedal. If the idle smooths out the problem is with a dirty/defective Idle Air Control valve.



Did the shop install high quality mounts?

Were the correct plugs installed?

The ones called for in the owner’s manual?

I guess the first thing I suspect is the mixture is too lean. Unmetered air is getting into the engine somehow. All the vacuum hoses and devices should be check one by one for leaks or defects. If you notice any unusual thing going on with the brakes coincident with the rough idling, suspect a failed brake booster. That is a common source of vacuum problems which result is rough idling.

Also check the easy stuff like the PCV valve and the EGR. Esp a stuck EGR can result in very rough idling.

If you can fix the problem by stepping on the gas pedal a bit; i.e. if increasing the idle speed slightly solves it, then suspect the IAC.

95 Chrysler New Yorker ,rough idle when at a traffic light.Not real rough. Checked fuel pressure .ok Replaced IAC helped ! replaced EGR solenoid assy., problem fixed. EGR Valve checked with vacuum,checked ok. Not replaced, very hard to get to. Probably should have. rough idle gone. I have service manual which helped a lot.