1.5T Rough Idle

[Yaminashi]

My Si has been acting strange here recently and I'm not sure if I'm just freaking out over something normal or if there is an actual issue. The car will idle kinda rough but it only happens after I get back and drive somewhere else and the engine is warm and the AC is on. What's also weird is that it only happens when it's on any sort of tune, if I switch back to factory it doesn't idle rough. Checked the spark plugs and they're all within the gap spec not showing any abnormal wear. I also recorded a datalog of the car idling in both factory and tuned as well as a bit of driving on both.

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[kytos]

I noticed that when the IAT are very hot after some idling with the AC working hard, the engine vibrates a lot, I notice it even more now because I have the Perrin RMM inserts. Funny thing is if I rev the engine a bit it disapears but comes back after 2 seconds. I'm using TSP stage1 (non-si) with ktuner. Sometimes when the AC is not working that hard or the engine isn't that hot it idles smoother. Worth mentioning I have my idle RPM rised up to 800.

 

[Yaminashi]

I noticed that when the IAT are very hot after some idling with the AC working hard, the engine vibrates a lot, I notice it even more now because I have the Perrin RMM inserts. Funny thing is if I rev the engine a bit it disapears but comes back after 2 seconds. I'm using TSP stage1 (non-si) with ktuner. Sometimes when the AC is not working that hard or the engine isn't that hot it idles smoother. Worth mentioning I have my idle RPM rised up to 800.

Yeah I haven't messed with the idle, but if I do rev the engine just a little it does the same thing as yours.

 

[Hollywoo0220]

@Yaminashi
Weather has been increasing in OH right? You are on an aftermarket tune and adding additional load to the engine running the A/C.
You very well may just be experiencing HEAT. You explain that it happens with the AC on and after you return from somewhere. You could very well just be "heat soaked" and the FLASH tune has a differrent idle perameter than the OEM spec.
Since, you report that the OEM tune has no issues, this would be my best stab at what you are experiencing. If you had a serious problem, it wouldn't go away regardless.

 

[Yaminashi]

@Yaminashi
Weather has been increasing in OH right? You are on an aftermarket tune and adding additional load to the engine running the A/C.
You very well may just be experiencing HEAT. You explain that it happens with the AC on and after you return from somewhere. You could very well just be "heat soaked" and the FLASH tune has a differrent idle perameter than the OEM spec.
Since, you report that the OEM tune has no issues, this would be my best stab at what you are experiencing. If you had a serious problem, it wouldn't go away regardless.

I figured it was something along those lines, I just wanted some sort of reassurance of that. But thanks for your insight!

 

[Hollywoo0220]

I figured it was something along those lines, I just wanted some sort of reassurance of that. But thanks for your insight!

I will assume that you are not experiencing performance loss, since you did not disclose that.
Use the scan with your tuning device and check to see if there are any codes.
Also, acquire a can of MAF cleaner and disconnect and clean that sensor and determine if the idle yet exists.
Often, a little residue on the MAF will cause rough idling. If indeed you are using an aftermarket intake or a high flow filter that uses an oil spray; that can slowly build up residue on the MAF.

You have already checked your plugs, so if you are so inclined - the next step after a MAF would be the throttle body, ECT sensor, or slight vacuum leak in the feed system.
Since your vehicle is so new, you should not have issues with the EGR or OXYGEN sensors. I have ruled fuel out due to the non disclosure of performance issues.
Just try cleaning the MAF and see if that cures your ailment.

 

[Yaminashi]

I will assume that you are not experiencing performance loss, since you did not disclose that.
Use the scan with your tuning device and check to see if there are any codes.
Also, acquire a can of MAF cleaner and disconnect and clean that sensor and determine if the idle yet exists.
Often, a little residue on the MAF will cause rough idling. If indeed you are using an aftermarket intake or a high flow filter that uses an oil spray; that can slowly build up residue on the MAF.

You have already checked your plugs, so if you are so inclined - the next step after a MAF would be the throttle body, ECT sensor, or slight vacuum leak in the feed system.
Since your vehicle is so new, you should not have issues with the EGR or OXYGEN sensors. I have ruled fuel out due to the non disclosure of performance issues.
Just try cleaning the MAF and see if that cures your ailment.

No performance loss at all, also have no codes showing up. I do have a Mishimoto intake that I reoil so it may be that. I'll grab some cleaner and check the MAF sensor.

 

[bbeem]

This is a good thread. After I installed RMM I get big vibration with AC on at idle. It's pretty extreme at idle but if I give it a c hair of throttle which is like 1400rpm it smoothes out. Wish I could throttle the rpm to like 1k or 1200 but the first progression from 1% is 5% dbw which puts me kind of high for idle close to 1500rpm. Anyhow it's completely typical with new RMM.

What botheres me is when I get the vibration WITHOUT the AC on! It probably happens at a stop maybe once every couple weeks. The vibration is about 1/2 or 2/3 as bad as when the AC is on. Revving rpm up will smoothen it but when I get back to 750rpm it won't go away. Sometimes letting off the brake and letting the car settle into a different position if not on flat ground can make it to away but usually not. Why this happens only like 1/100 stops is puzzling. And I've never ran auto AC, I flip it on manually and only run at "Lo" when on (because if you run a temperature setting it's actually applying heat to the ac'd air.) When this happens like every other week I always check the AC out of habit, it's always off... I just don't like that every once in a while it vibrates like this without ac on. Maybe the alternator can be a big enough load sometimes to make it rough?

 

[Yaminashi]

This is a good thread. After I installed RMM I get big vibration with AC on at idle. It's pretty extreme at idle but if I give it a c hair of throttle which is like 1400rpm it smoothes out. Wish I could throttle the rpm to like 1k or 1200 but the first progression from 1% is 5% dbw which puts me kind of high for idle close to 1500rpm. Anyhow it's completely typical with new RMM.

What botheres me is when I get the vibration WITHOUT the AC on! It probably happens at a stop maybe once every couple weeks. The vibration is about 1/2 or 2/3 as bad as when the AC is on. Revving rpm up will smoothen it but when I get back to 750rpm it won't go away. Sometimes letting off the brake and letting the car settle into a different position if not on flat ground can make it to away but usually not. Why this happens only like 1/100 stops is puzzling. And I've never ran auto AC, I flip it on manually and only run at "Lo" when on (because if you run a temperature setting it's actually applying heat to the ac'd air.) When this happens like every other week I always check the AC out of habit, it's always off... I just don't like that every once in a while it vibrates like this without ac on. Maybe the alternator can be a big enough load sometimes to make it rough?

Yeah I've never had mine vibrate like this when the AC is off just whenever it's on.

@Hollywoo0220

Also noticed on my way back home that it seems to do it when the timing is between -1 through 0. Not sure if that plays a factor into anything or not.

 

[Hollywoo0220]

Yeah I've never had mine vibrate like this when the AC is off just whenever it's on.

@Hollywoo0220

Also noticed on my way back home that it seems to do it when the timing is between -1 through 0. Not sure if that plays a factor into anything or not.

Well, you shouldn’t have any timing that low anyway. WHAT is your idle speed?
Just try the MAF and as long as you haven’t goofed with the voltage cleaning it might clear you up.
If not, try raising your idle by a 100?

 

[bbeem]

If not, try raising your idle by a 100?

Can you adjust you're idle in ktuner with the preconfigured tsp tune? Or would I have to have them make changes since much is locked out?

 

[Hollywoo0220]

Can you adjust you're idle in ktuner with the preconfigured tsp tune? Or would I have to have them make changes since much is locked out?

Yeah, not with the TSP since they lock that. Uncertain if they would do it even if you requested it. Might push you in the direction of a custom tune if you were to choose.

 

[Yaminashi]

Well, you shouldn’t have any timing that low anyway. WHAT is your idle speed?
Just try the MAF and as long as you haven’t goofed with the voltage cleaning it might clear you up.
If not, try raising your idle by a 100?

Idle is around 700-735 I think, not sure. Would have to check the datalog or wait until I drive the car again. I did buy some cleaner and I'm cleaning and reoiling my air filter.

 

[Hollywoo0220]

Idle is around 700-735 I think, not sure. Would have to check the datalog or wait until I drive the car again. I did buy some cleaner and I'm cleaning and reoiling my air filter.

Be very mindful with the quantity of oil you apply. Doesnt take very much. Pink is better than full on Red. Let it dry a little to and use a nice cloth or paper towel to rub off any residual oil on the top surfaces.

 

[Yaminashi]

Still has the same issue. Every after cleaning the MAF and air filter. Seems like it's just when the car gets heat soaked.

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