+2

 

How exactly is this slow dropping of RPM's supposed to help the emissions? Not meant as a smart-*** response, but I'm really curious.

Does this happen only in 3rd gear or during rev matching too (ie, when clutch is in)?

I'd figure it would have some effect in track driving. Imagine shifting down from 4th to 3rd, heel and toeing and on the brakes at all times. Once you shift into 3rd and let out the clutch, your brakes would be fighting the slow droping 3rd gear as it wants to keep on going... would that not be the case? Or does this feature turn off while braking and comes on only when egine braking without using the brake.

 

warrtalon, I have noticed this in my '05 also. Thanks for pointing it out.

 

do have an aftermarket tb? if so your tps might be off? sometimes when i put mine in neutral it will self-rev to about 3k then drop because my tps is broken

 

bone stock - i also notice that when i turn on my ac, engine revs to 2k before SLOWLY dropping back down to normal idle

 

My 06 dose it also.

 

Xtnct asked a very important question, and it sparked my curiosity. How is the slow dropping of RPM's supposed to help the emissions? And this question goes out to the guys who flashes ECU; is it possible that this phenomenon can be turned off with ECU tuning such as removing the rev limiter (not saying it’s wise to remove the rev limiter)?

 

Bump for these answers.

 

and bump again

 

I have two remarks to say:


1) it use to happen to me when I had the 5k rev limiter disconnect. Al suggest to plug it back in and problem dissapeared
2) When I hap the problem it would happen only in the highrpm and it would stay specially if you shifted down quickly then to neutral.

As long as you have it in gear it shouldn't do it, it happens when you put the car in neutral after high reving.


just my .2c

Carlos

 

Madcow: I remember how my old WRX used to do that. It drove me freakin' crazy. It is for emissions (slamming the throttle shut suddenly can result in a puff of unburned fuel). It was so annoying to me.. I had to shift slower to wait for the stupid revs to drop. My friend's Ford Focus is the same way. I had no idea Mitsu screwed up the '05+ EVOs too.

On cars which don't yet have throttle-by-wire, there is an air bypass valve (usually called an Idle Air Control - IAC valve) that is used to bypass air around the throttle butterfly. The computer controls a solenoid that opens the valve to keep the revs up. This is the same way the computer holds revs higher when the engine is cold. If you block that valve off, you should be disabling this stupid 'feature' (or maybe just a switch to open the solenoid circuit that you could toggle from the cockpit). However, that may also result in cold start problems. I was planning on trying my theory out on the WRX, but just sold it for the EVO instead.

Good luck,

Rob

 

i had a check engine becouse of that.
i will post details tomorrow...

you will just have to clean an accelerometer plug!

 

[QUOTE=xtnct]How exactly is this slow dropping of RPM's supposed to help the emissions? Not meant as a smart-*** response, but I'm really curious.

I beleive it just allows the motor to burn off any unburnt fuel in the cylinders.

 

My 06 does that after WOT. Pressing the clutch pedal once or twice brings things back to normal.

 

1. failed idle speed control servo
2. open/short circuit in idle speed control servo circuit or loose connector contact
3. failed engine ECU

These are the 3 cases for that...the most probable is the connector!