Occasional rough idle, anyone else?

[Rusherific]

I tried searching and couldn't find much. This is a very recent thing that I've only noticed starting a few weeks ago (1k miles before without this issue). I'm pretty sure it only happens once temps are up and the engine goes down to its lowest idle, sometimes at a stop light, after a few seconds of smooth idling it will noticeably dip down in rpms just a little, and start to get a little shaky, to where you can hear and feel the engine stumbling a bit. It only happens maybe once or twice a drive, sometimes more often than that, sometimes never in a single drive. And so far hasn't caused any actual driving problems yet. No warning lights or anything. I wouldn't call it a full on miss but you can feel the car shake a little when it's doing it.

Just curious if anyone else has had this absent any other problems?

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[RPDBlueMoon]

I tried searching and couldn't find much. This is a very recent thing that I've only noticed starting a few weeks ago (1k miles before without this issue). I'm pretty sure it only happens once temps are up and the engine goes down to its lowest idle, sometimes at a stop light, after a few seconds of smooth idling it will noticeably dip down in rpms just a little, and start to get a little shaky, to where you can hear and feel the engine stumbling a bit. It only happens maybe once or twice a drive, sometimes more often than that, sometimes never in a single drive. And so far hasn't caused any actual driving problems yet. No warning lights or anything. I wouldn't call it a full on miss but you can feel the car shake a little when it's doing it.

Just curious if anyone else has had this absent any other problems?

I don't know if its the same exact problem but I think I know what you are describing, can't say that I have a drop in rpms, but it does feel like the engine takes a deep breathe and will rough idle for like half a second. There is definitely a difference in the idle tone.

First time it happened I thought the engine was going to die, but everything is fine so I'm sure its normal. If something was wrong I am pretty sure my engine would be dead by now because I have been driving it really aggressively for the past 1,000 miles (I'm at 3,000 now) with several redline pulls and staying high up in the RPMs. I replaced the resonators with the LTH one and it is so fun to drive.

 

[Rusherific]

I don't know if its the same exact problem but I think I know what you are describing, can't say that I have a drop in rpms, but it does feel like the engine takes a deep breathe and will rough idle for like half a second. There is definitely a difference in the idle tone.

First time it happened I thought the engine was going to die, but everything is fine so I'm sure its normal. If something was wrong I am pretty sure my engine would be dead by now because I have been driving it really aggressively for the past 1,000 miles (I'm at 3,000 now) with several redline pulls and staying high up in the RPMs. I replaced the resonators with the LTH one and it is so fun to drive.

Yeah I mean I assume with a modern engine like this it would throw a code if something was wrong? Just odd it started happening out of nowhere and doesn't happen all the time either. It definitely lasts for more than ahalf second for me. Usually if it starts will stay that way until I rev or get going again

 

[RPDBlueMoon]

Yeah I mean I assume with a modern engine like this it would throw a code if something was wrong? Just odd it started happening out of nowhere and doesn't happen all the time either. It definitely lasts for more than ahalf second for me. Usually if it starts will stay that way until I rev or get going again

Yeah thats my assumption. A code would pop up or something or something would be wrong with the acceleration or something I guess. I'll pay more attention next time it happens but yeah if there was something wrong my engine would be completely fucked by now, I check the oil and everything is fine. I never owned a car with a big V8 like this so I assume its normal

 

[JR369]

Does this coincide with the AC compressor being on?

 

[Rusherific]

Does this coincide with the AC compressor being on?

That's a good question I'll have to test it out. I feel like I definitely have drove this summer in very hot weather+AC and didn't notice the issue, but will test and see if it's related!

 

[JR369]

My R has actually quit at a stop light before on very hot TX days. It happened twice. After I blip the throttle at a stop light and the motor rpm fell down well below idle and it stumbled to get back up and quit. I was like WTF? I started it back up and on we went.

 

[MikeR397]

Check the wires on top, look for breaks or splits. I think they are the ones that control the camshaft actuators. They sag from heat and break and when two of them broke on me, I got a rough idle.

 

[Rusherific]

My R has actually quit at a stop light before on very hot TX days. It happened twice. After I blip the throttle at a stop light and the motor rpm fell down well below idle and it stumbled to get back up and quit. I was like WTF? I started it back up and on we went.

Huh, yeah at the time I remember thinking how well mine did the one day where we hit like 30 minutes of bumper to bumper traffic in 100 degree heat after just finishing a....spirited mountain drive, so if it's heat or AC related that definitely wasn't always the case for me.

 

[Rusherific]

Check the wires on top, look for breaks or splits. I think they are the ones that control the camshaft actuators. They sag from heat and break and when two of them broke on me, I got a rough idle.

I'll take a look, but should that be happening at 1.3k miles?? Also do you not get a check engine light from that?

 

[SL8888]

Yes I have had the same experience with my 19. It has not stalled but I was concerned the first couple of times. When I drove it from the dealership Dec. 30, 2019 it had 5.3 miles on it. Now it has 4,957.4 miles on it. The only "enhancement" to the engine is a resonator delete X pipe from Lethal Performance. What bugs me more is how slow the RPMs drop when I lift off the accelerator. Mechanic at the dealership said they do that for "Rev" matching between shifts....I don't believe that. Enjoy your GT-350 Merry Christmas & Happy New Year !

 

[Nfs1000f]

May 2017 will have an occasional stumble. Has not thrown a code.

 

[TX5OH]

@Rusherific Is it similar to this?......

 

[Rusherific]

@Rusherific Is it similar to this?......

Interesting, it's not quite as bad for me as in that video. I also tried messing with the AC today and no effect. I'm gonna peek under the hood here in a minute to look at the wiring but it seems to happen before the engine's fully warmed up and run out a few times, after that it seems to no longer happen.

I have noticed also that after stopping and starting the car again is usually when it's worst. In fact a number of times, leaving a gas station it feels like the car is almost going to stall getting going in 1st, with a jerk like I let the clutch out too fast or the hill-assist is acting up. It's literally the only time I notice it and then the car is fine the entire rest of the time. It's probably the most repeatable way that it happens (of course not today though).

Also I read a comment on that youtube above that said they had their dealer tell them it's a traction control issue. So for the hell of it I tried flipping traction control off the one time I got a rumbly idle today and I swear it might have helped, but the light was turning green and kind of cut that experiment short so I can't be sure that actually happened or not.

In short it can happen randomly at any time it seems, but most often during warm up, or else right after stopping and starting the car again, even at full temps.

 

[AhuraPro]

What bugs me more is how slow the RPMs drop when I lift off the accelerator.

You can fix that with a lighter flywheel and 0 Weight motor oil.

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