idle take awhile to settle?

[NocturnalEmber]

6MT cars only I'm guessing.

Even when warm, when I put my car into neutral (approaching a stoplight, etc, anything that would necessitate me putting it in neutral) the idle seems to want to hang at/around 1,500 and takes about 10~ seconds to slowly dip back to normal idle speed (750~.)

This wasn't an issue before I got my muffler delete, but now that I can actually hear the car, this idle hang seems really annoying.

Anyone have this happen to their cars? Considered taking it to the dealer but I'm not expecting much on that front.

 

[alienpoker]

Are you coming from say 3rd to Neutral? Turn off rev match & see if it goes away.

When the Z thinks you may downshift, it starts to rev-match. When you don’t select the lower gear, after a few secs the idle settles. My 370Z MT always does this in S-mode.

I dk if this is what you are describing, but there are other threads that describe rev hang. The link discusses installation of a lighter flywheel, which will help. But it does give the car a pronounced ’chatter’ at idle and a different pitch with the clutch in-which I have listened to on a Z. I would personally find the chatter even more annoying to rev hang.

 

[NocturnalEmber]

Are you coming from say 3rd to Neutral? Turn off rev match & see if it goes away.

When the Z thinks you may downshift, it starts to rev-match. When you don’t select the lower gear, after a few secs the idle settles. My 370Z MT always does this in S-mode.

I dk if this is what you are describing, but there are other threads that describe rev hang. The link discusses installation of a lighter flywheel, which will help. But it does give the car a pronounced ’chatter’ at idle and a different pitch with the clutch in-which I have listened to on a Z. I would personally find the chatter even more annoying to rev hang.

This can be 1st to neutral, 2nd to neutral, 3rd to neutral, its every time. 10mph in a parking lot coasting to a stop? does it. Coming to a stop from 3rd? does it.

I've tried it without S mode on, it still does it. 10+ seconds of the idle holding at 1,500 and slowly dropping to idle doesn't seem like something S mode would do though. That seems too long for rev hang as well.

This isn't after an aggressive shift or high rpm neutral drop, I might be at 3k when I put it into neutral.

The way it behaves is like an older car slowly dropping idle as it warms up (but in this case the car is fully warmed up.)

 

[CPerdomo]

6MT cars only I'm guessing.

Even when warm, when I put my car into neutral (approaching a stoplight, etc, anything that would necessitate me putting it in neutral) the idle seems to want to hang at/around 1,500 and takes about 10~ seconds to slowly dip back to normal idle speed (750~.)

This wasn't an issue before I got my muffler delete, but now that I can actually hear the car, this idle hang seems really annoying.

Anyone have this happen to their cars? Considered taking it to the dealer but I'm not expecting much on that front.

That is exactly what's been in my mind since I also did the muffler delete. Now that I have a Nismo, I thought that being AT would change the idle... but it doesn't. I think the idle is too high.

 

[alienpoker]

This can be 1st to neutral, 2nd to neutral, 3rd to neutral, its every time. 10mph in a parking lot coasting to a stop? does it. Coming to a stop from 3rd? does it.

I've tried it without S mode on, it still does it. 10+ seconds of the idle holding at 1,500 and slowly dropping to idle doesn't seem like something S mode would do though. That seems too long for rev hang as well.

This isn't after an aggressive shift or high rpm neutral drop, I might be at 3k when I put it into neutral.

The way it behaves is like an older car slowly dropping idle as it warms up (but in this case the car is fully warmed up.)

Okay. It’s not S-mode & not a rev hang as it’s only when going from gear to neutral.

Seems like you only get it when the engine goes to idle from being under load. One thing that springs to mind is a small vacuum leak- or an exhaust leak before the O2 sensors. The ECU would then increase fuel to the injectors, to make up for the extra air & what it detects as a lean condition. That could explain the idle running high when load is taken off the engine. The only way to be sure of that is for a mechanic to do a ‘smoke test’ in the engine bay, or check for an exhaust leak which should be obvious.

If it’s a large leak, I would expect it to ‘hunt for idle’ or throw a fault code. You could try to look at ODBC live data. There is some info there that can show long/short term fuel trims. Some ODBC scanners/apps can graph data- idle vs. fuel trims could be a way to examine and document what is happening. Comparing that to someone else’s data with a MT could help pinpoint if it’s a more general thing. Sorry, I have an AT so my data won’t be any help.

You haven’t changed anything in the intakes, only the exhaust?

 

[takemorepills]

It's normal.

Almost all cars with a manual transmission made in the last 15 years will do rev hang.

By letting revs drop quickly, there's a little bit of unburned hydrocarbons generated, the EPA didn't like that, so cars with manual transmission get rev hang programmed in to reduce the HC output between gear shifts or going to neutral. Some cars have more or less rev hang, depending on what it takes to address the excessive HC dump.

 

[kevinbonds]

It's normal.

Almost all cars with a manual transmission made in the last 15 years will do rev hang.

By letting revs drop quickly, there's a little bit of unburned hydrocarbons generated, the EPA didn't like that, so cars with manual transmission get rev hang programmed in to reduce the HC output between gear shifts or going to neutral. Some cars have more or less rev hang, depending on what it takes to address the excessive HC dump.

This is correct, I've had several manual cars that were older and did not have the ECU rev hang issue and it makes the car so much smoother. I have a 2024 Z performance and the 1-2 shift annoys the hell out of me, due to the rev hang, I would get tuned just to fix that. I wonder if that can be done with ECU tech software.

 

[77AkumaNoZetto]

So from what I've learned the culprit is the dbw electronic throttle body that is controlled by the vehicle ECU, almost all new vehicles suffer from this. It is the most annoying thing, my 17 WRX STi has that too and at first I didn't know so in my infinite wisdom I installed an ORC super single metal clutch with a lightened flywheel, I figured that would at least solve some of that. Surprise was big fat no.

 

[NocturnalEmber]

Car has nismo intakes (I had the dealer install them for warranty cya purposes.)

I'm not so sure this instance is a new car thing. Could be, but my Supra didn't do it, and neither does my partners Mazda 3 (all MT cars, and < 10 years old.)

I guess I could take it to the dealer and see, but I doubt anything will come of it.

 

[takemorepills]

Car has nismo intakes (I had the dealer install them for warranty cya purposes.)

I'm not so sure this instance is a new car thing. Could be, but my Supra didn't do it, and neither does my partners Mazda 3 (all MT cars, and < 10 years old.)

I guess I could take it to the dealer and see, but I doubt anything will come of it.

Depends on the vehicle. If a certain engine design requires more "hang", then it gets programmed in. BMW and Mazda spend a lot of effort on their engine designs, I am sure they have "hang" designed into them as well, but they probably needed less of it, and it seems unnoticeable to most.

Even old EFI vehicles were designed to prevent the throttle from closing too quickly, anyone who has worked on pre-DBW vehicles has seen the dashpot on the mechanical throttle body that controls sudden throttle closure. How much you notice it on each unique vehicle depends on lots of variables. I have seen many Corolla GR owners complain about rev hang, and that car has a tiny 3 cylinder with very little rotating mass, if you don't know about intentional rev hang, then it seems odd that it would happen on a sporty, lightweight engine....

 

[thesilverbullet]

mine does this as well.

with no load coasting up to a stop sign the idle is slow to drop after i push in the clutch. im guessing an EcuTek tuner could tune this away.