2014 XLT 3.5L intermittent RPM drop at idle- any suggestions?

[DiosmioMan]

2014 XLT 3.5L intermittent RPM drop at idle- any suggestions?

While driving last week there were two separate occasions when my XLT would suddenly drop to around 300 rpm and feel like it was about to stall out and then would immediately rebound up to around 600 rpm’s. This only happened after driving for a bit and then stopping (once for a 30 minute traffic jam where no one moved, and once when I stopped at a store to let my son run in to grab something). Each incident involved 4-5 of these rpm drops. No codes have popped up. I know she is due for new spark plugs; the air filter is a new K&N drop in and I have run 2 bottles of Techron fuel injection cleaner through the gas tank a month or two ago.

Apart from needing new spark plugs I figured I would swap out the PCV valve tomorrow. Any other ideas or suggestions for troubleshooting? This thing runs great under throttle but those near stall incidents were somewhat unsettling.

Thanks in advance for the advice!

 

[peterk9]

Did you change the spark plugs? How many miles are on the vehicle?
Merry Christmas.

Peter

 

[DiosmioMan]

Did you change the spark plugs? How many miles are on the vehicle?
Merry Christmas.

Peter

Thanks for the follow up. Spark plugs are still on the to-do list. I cleaned the MAF sensor and the throttle body. And I checked the voltage on the battery and it was showing 11.8 volts (about 30%) so she got a new battery too. Running like a champ now.

 

[J_C]

While yours appears to have had a different issue, there is also a known issue with the 3.5L including your model year and that happened to my '14 w/3.5L NA engine but only on a single tank of fuel at idle.

The issue is the PCM doesn't increase the engine RPM under certain instances of the A/C compressor kicking on, but then senses the drop in RPM and immediately switches the compressor back off. There's a TSB for it, 15-0149 and a video elaborating on youtube:

https://static.nhtsa.gov/odi/tsbs/2015/SB-10074752-7690.pdf

I never had the newer tune flashed to my '14 because the issue went away after I refuelled. It also had no driveability issues on that tank of gas, just the idle dropping low with A/C compressor engagement.