Intermittent rough idle

beetle · May 27, 2023

2014 GMC, 65K miles, original owner......occasionally when coming to a complete stop, the engine will have a slight rough idle, other times I have to look at the tach to see if it's still running. Started recently..........anyone else experience this?

mikeyk101 · May 27, 2023

Have you gotten a check engine light recently? The reason I ask is that mine would get an occasional rough idle mostly when starting a cold engine and occasionally while stopped at a stop light. It started towards the end of 2021 over the course of next couple months I had the check engine light come on twice with a code P050D. I cleared it both times and it stayed off for some time. It came on a 3rd time early 2022 and I decided to have it looked at. That was at about 69,000 miles. Prior to bringing it in, I did a scan with my OBDII scanner and this time besides the P050D showing up, I also got a P300 (misfires) which was why I decided to get it looked at. They diagnosed it as a fuel injector on cylinder 1 was sticking open. Once that was replaced, no more idle problems. It's been nice and smooth ever since.

If you don't have one, you can get a Bluetooth OBDII scanner for around $20-25 dollars on Amazon and use an app like TorquePro to at least run a scan. Or even take it by an Auto Zone or O'Reilly's and ask them to scan it. You may find stored codes that haven't activated the check engine light but will let you know if there's a potential problem.

mikeyk101 · May 27, 2023

Just to add, I also changed out the spark plugs myself after getting it back with new fuel injector at as it was probably about time. But between the fuel injector and new sparkplugs, I haven't had any issues since.

beetle · May 27, 2023

Good info, thanks!

beetle · May 27, 2023

BTW, no Check Engine lights.

rav3 · May 27, 2023

Have you looked at cleaning your throttle body. These get Carboned up & the clearance reduces between the flap & housing. Search YouTube for some ideas on what to do & what not to do. It will need to go thru a relearn afterwards. Just a thought at your miles.

Edited May 27, 2023 by rav3

mikeyk101 · May 27, 2023

Good suggestion. It sounds intimidating but is fairly easy to remove the throttle body for cleaning. And might not be a bad idea to clean the MAF sensor at same time. Again, super easy but just make sure to use the proper MAF cleaner so you don't damage it...