Rough idle?

[REBELXSi]

I just crossed 20k recently. I bought the car new about 10 months ago. A few days ago, I noticed my car was idling rougher than usual. The car isn't shaking or anything but the idle is audibly louder and rougher. The car is idling @ 700rpm

I'm at 40%/5000mi into this oil change but I've been further into oil changes obviously and there hasn't been an issue before.

I've had a muffler delete for about 3 months and even with that, the idle sound was nearly OEM level. Not sure what changed within the last week at most. Oil level is fine and I haven't done anything under the hood lately other than check the oil today.

The car is stock other than a CAI... FWIW.

Any ideas? I'm probably going to change the oil early to see if that helps but I doubt that's the problem.

Edit: I unplugged the battery and let the car idle for a while and then took it for a ride. Doesn't seem to have changed anything although my steering did feel lighter during the drive. I think that was the first time I felt a real difference in sport/non sport mode lol

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[JT Si]

What CAI are you using? Do you have a tune?

 

[amirza786]

I just crossed 20k recently. I bought the car new about 10 months ago. A few days ago, I noticed my car was idling rougher than usual. The car isn't shaking or anything but the idle is audibly louder and rougher. The car is idling @ 700rpm

I'm at 40%/5000mi into this oil change but I've been further into oil changes obviously and there hasn't been an issue before.

I've had a muffler delete for about 3 months and even with that, the idle sound was nearly OEM level. Not sure what changed within the last week at most. Oil level is fine and I haven't done anything under the hood lately other than check the oil today.

The car is stock other than a CAI... FWIW.

Any ideas? I'm probably going to change the oil early to see if that helps but I doubt that's the problem.

Edit: I unplugged the battery and let the car idle for a while and then took it for a ride. Doesn't seem to have changed anything although my steering did feel lighter during the drive. I think that was the first time I felt a real difference in sport/non sport mode lol

Could maybe just be the weather, humidity conditions etc. Colder, wetter conditions may cause the idle to go down more, also if you have CAI and the weather is wet, possibly some moisture may be getting in. I find my car runs the smoothest between 55 degrees F and 90 degrees F and humidity is lower. On cooler mornings when there is a lot of moisture in the air performance seems slightly less

 

[REBELXSi]

What CAI are you using? Do you have a tune?

The Cobra Street. No tune. I've had it since last summer no issues.

 

[REBELXSi]

Could maybe just be the weather, humidity conditions etc. Colder, wetter conditions may cause the idle to go down more, also if you have CAI and the weather is wet, possibly some moisture may be getting in. I find my car runs the smoothest between 55 degrees F and 90 degrees F and humidity is lower. On cooler mornings when there is a lot of moisture in the air performance seems slightly less

Definitely not wet. I've been through some crazy weather with this thing with no issues. Guess we'll see what happens when I change my oil

 

[amirza786]

Definitely not wet. I've been through some crazy weather with this thing with no issues. Guess we'll see what happens when I change my oil

I changed my oil after 7K and 20 percent left on the MM and didn't have any issues with idle or performance. Hopefully that fixes it

 

[Hollywoo0220]

I just crossed 20k recently. I bought the car new about 10 months ago. A few days ago, I noticed my car was idling rougher than usual. The car isn't shaking or anything but the idle is audibly louder and rougher. The car is idling @ 700rpm

I'm at 40%/5000mi into this oil change but I've been further into oil changes obviously and there hasn't been an issue before.

I've had a muffler delete for about 3 months and even with that, the idle sound was nearly OEM level. Not sure what changed within the last week at most. Oil level is fine and I haven't done anything under the hood lately other than check the oil today.

The car is stock other than a CAI... FWIW.

Any ideas? I'm probably going to change the oil early to see if that helps but I doubt that's the problem.

Edit: I unplugged the battery and let the car idle for a while and then took it for a ride. Doesn't seem to have changed anything although my steering did feel lighter during the drive. I think that was the first time I felt a real difference in sport/non sport mode lol

If you are idling at 700rpm then you are doing ok there.
I am assuming that the needle is not "bouncing" (as you didn't state that in your post).

You may wish to try cleaning the MAF.

With the idle not bouncing, that is first thing to check.

 

[Cscott_xGen]

Some thought....

-You are waiting to long for your oil changes. 3k is a sweet spot
- Using the ac can affect the idle
- I had spark plug failure at 26k- check your plugs

 

[Justin]

I’ve noticed throughout my ownership of my si that it’s gotten louder. I’m at. 56k miles and it’s NOTICEABLY louder than when u first got it. Only mod is my cobra cai

 

[fenix-silver]

Check fuel trims.

 

[Cscott_xGen]

Also possible walnut blasting may be needed.

 

[REBELXSi]

Also possible walnut blasting may be needed.

If I needed to clean my intake valves after 20k I'd sell the car.

 

[REBELXSi]

Check fuel trims.

Car is completely stock minus intake. No tune.

 

[fenix-silver]

Car is completely stock minus intake. No tune.

Yes, but fuel trims can help with locating the issue.

 

[REBELXSi]

Yes, but fuel trims can help with locating the issue.

Lol oh, I thought that was just for tuned folk. I have no idea how to do that.

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