2009 Rogue - Rough Idle on Cold Engine Startup

[direavenger]

Hey all,

Having an issue with my 2009 Rogue SL AWD w/ 57k miles. For the past couple of months, I've been experiencing a rough start when the car is started the first time for the day. The car turns over just fine, but the idle will fluctuate for approx 10 seconds from 2k RPMs to less than 500. After the engine has warmed up, we don't tend to see the issue (yet...). Idle evnetually settles to approx 750 RPMs. It's been getting worse over time, to the point where I believe it might actually stall.

Dealer has looked at it a couple of times. First was an engine idle relearn, which did nothing. More recently, he replaced the engine air filter and did a fuel injector clean, which also did nothing. He added a can of BB44k to the gas tank and recommended we fill with premium gas for the next couple of fillups. I'm not holding my breath for that one. He said next step is likely a throttle body replacement, because cleaning this "finicky" throttle body isn't an option (his words, not mine).

Some background: this car was driven short distance for the first four-ish years of its life (2-ish miles to a park-and-ride each day), with periodic long-distance trips. For the last 2 years, it's been doing a longer daily commute (70-ish miles round trip). All dealer recommended service has been performed at Nissan of Hawthorne (NJ).

Any thoughts as to what might be the culprit, or things I can try myself to help diagnose? I'm a technical person and pretty handy, but with minimal experience wrenching on cars.

Thanks in advance for your help.

[Rogue One]

Rough Idle

1. If the car starts when cold but, idles rough or does not want to stay running, this can indicate a problem with the engine temperature sensor. When the engine is started cold, the engine temperature sensor sends a signal to the DME control unit to provide a richer mixture. As the engine temperature sensor starts to fail, it sends a higher than actual temperature signal to the DME control unit. The DME control unit leans the fuel mixture thinking the engine is at normal operating temperature. This causes the engine to run rough. As the engine warms, it not longer needs the richer cold idle mixture and the engine runs smoother.
2. If the car idles rough this can also be indicative of bad plug wires, distributor, or rotor. One way to check for bad plug wires is to inspect the plug wire runs with the car running in a very dark area. If the plug wires are bad you should see some arching to the cylinder head or fuel rail.
3. If the car idles rough or cuts off at low RPM or idle, the cause could be a failing O2 sensor. The O2 sensor is out of the loop at full throttle and will not affect the way the car runs.
4. A rough idle can also be caused by a problem with the air flow box. The damper for the air flow box can fail mechanically or the contacts inside the box can get dirty and send a errant signal to the DME control unit. This can sometimes be corrected by cleaning the electrical contacts inside the air box. This requires removing the cover on the air box which is held in place by caulk. You will need to cut through the caulk and gently pry the cover off. Once the cover is removed, clean the circuit board inside with a good contact cleaner. When you have finished cleaning the circuit board, reattach the cover using a non-corrosive caulk.
5. If the car experiences a rough idle or idle fluctuates several hundred RPM, this can indicate a sticking idle stabilizer valve. Many people have removed and cleaned them but, this is normally a temporary fix and the valve should be replaced. A faulty O2 sensor can also cause RPM to fluctuate at idle. Unplug the O2 sensor and see if the idle still fluctuates.

[darylzero]

Try cleaning your MAF sensor as well. Quick and very easy, you can do it yourself.