AFR Spike at Idle

[JGT_TreeFiddy]

Gents,

Within the past month, I've began to notice something a little strange and I'm curious if anyone has experienced a similar issue. My car is a '17 with 6,600 miles, I'm the 2nd owner and there seems to be no signs or concerns regarding oil consumption. During my ownership tenure, the car has run flawlessly and it's seen it's fair share of 7k+ pulls around town.

However, I daily drive the car and lately, while either sitting in traffic or at a light, I've noticed that at idle the car will randomly sputter or give off a sort of misfire sensation. This is 100% noticeable, as you can feel the car recover very quickly and if standing behind the car, it's very noticeable within' the exhaust note.

With that being said, I've always kept a close eye on my AFR, just out of habit and while normally I see the car idling around 13.8-14.4; when this issue occurs, the AFR will spike to around 15.6-15.9 and then re-settle. I don't notice any problems at WOT and the car runs perfectly otherwise. No CEL's have been thrown and at this point, I'm not too concerned, but curious what some of your thoughts may be. I'm not sure why the car would try to go lean for a split second and then be perfectly normal. My first couple guesses were bad gas or open loop, but neither of those seem to be the case.

Let me know your thoughts. Appreciate it!

Jay

Sponsored

 

[Demonic]

Have you checked for any soft codes that could have been thrown?

 

[DCShelby]

Dirty air filter? They get dirty really fast. Still on the original one?

 

[SVTinAR]

Some one in another thread recently brought up that the plug gap on earlier year GT350s is spec'd pretty wide and has been reduced in recent year GT350s - which might explain the occasional hiccup at idle we sometimes experience. Seems owners of newer 350s generally think they idle a little better without the occasional hiccups (a miss?). Sounds reasonable to me but who knows for sure? That could also explain the spike in the AFR gage as the exhaust sensor detects it. Mine bounces around a lot at idle all the time.

 

[TDC]

At idle a slight hesitation or what sounds like a extremely short miss is typical for the 16-18. All other throttle positions there shouldn’t be any such behavior. Thread below discussed it.

https://www.mustang6g.com/forums/threads/gt350-miss-at-idle.114606/

Now if you are saying the rpm’s drop substantially during the time of the miss than that doesn’t sound like what I described above.

 

[Tomster]

I had an intermittent p0020 code recently (camshaft position sensor). It caused an occasional rough idle and affected the overall power output of the engine. It also caused the sputtering backfire between shifts, just as you describe. You might want to have your tech do a wiggle test on the harness connectors that attach to your valve covers. Mine was hanging by a thread. Bingo. She's running like a raped ape now.

Get forscan onto a laptop with a bluetooth OBDII reader, or even a standard OBDII reader to see if you have a pending code.

 

[Nfs1000f]

The Ford Pass app has a featured called Vehicle Health Alerts and Vehicle Health Report. There is some set up you have to do on your SYNC system. I do not know how detailed the information would be but it may be worth a try.

 

[Blakejordan]

I had an intermittent p0020 code recently (camshaft position sensor). It caused an occasional rough idle and affected the overall power output of the engine. It also caused the sputtering backfire between shifts, just as you describe. You might want to have your tech do a wiggle test on the harness connectors that attach to your valve covers. Mine was hanging by a thread. Bingo. She's running like a raped ape now.

Get forscan onto a laptop with a bluetooth OBDII reader, or even a standard OBDII reader to see if you have a pending code.

can you direct me which plug it is exactly, i am having the same code :( what did you do exactly to fix it?

 

[honeybadger]

can you direct me which plug it is exactly, i am having the same code :( what did you do exactly to fix it?

Sponsored