Rough idle

[Bizzenn]

I have posted this before but it did not show up on here. So here's the issue. When in Drive and when the a/c is off, the Rpm's hover around 550-600 causing and annoying shake. When the a/c or the front defroster is on the Rpm's jump to 700 and it smooths out. It does none of this in reverse however. Also, on e I lift off the brake pedal to accelerate, it goes away as soon as My foot leaves the brake pedal. Anybody have this issue? I'm beginning it's yet another trait of the damned cvt or torque converter.

[Ronzuki]

That idle seems rather low...I'll need to take notice of mine tonight on the drive home. There's probably a spec buried in the service manual as to what it should be. It almost sounds as though the tail lights are putting enough strain on the alternator to cause the idle to lower even further. This happens a lot when I'm flat towing my Samurai behind our suburban and I turn on the burb's headlights and running lights for both vehicles via the suburban's tired, old, half-corroded electrical system. Hit the brakes and it drops even further (two sets of brake lights). Even the turn signals (2 vehicles worth) causes the volt meter to dip and the idle to fluctuate in sync w/ the flash pattern when I'm sitting at a traffic stop.
When you take your foot off the brake (and before you accelerate) try turning on your lights, high beams and fogs to put a different electrical load on it. When the A/C compressor is told to run, that's normally an input to the ECM that will cause the idle to bump up a bit, as you are noticing, to negate the added strain by the alt. Other, normal, electrical loads don't usually increase idle. How old is your battery in this car? A weak battery in modern day cars causes all kinds of strangeness.

[Bizzenn]

I will most definitely try this. My car Is a 2012 so the battery is only 2 years old. It also acts like it wants to stall when coming to a stop but again, only with air off. What puzzles me though is that it will run fine with the defroster on with the ac compressor off. I will try the light trick though. Thanks!

[Ronzuki]

Defroster mode almost always activates the compressor to dehumidify in modern vehicles, even if the 'A/C' light is not lit. This was instituted many years ago, in most autos, as no one would ever run their A/C in the winter. Once cars started being regularly equipped w/ A/C, us old timers learned turning the air on in winter while in defrost would clear the fog off the inside of the windshield quickly. One of those things that should be done once a week or so for 10-15 minutes to keep the oil in the refrigerant flowing through the system which in turn keeps the seals lubricated and things exercised. Now it just happens on its own as soon as you switch to defrost. Compressor on, idle up.

[Bizzenn]

Something just occurred to me. Could a dirty air filter cause this due to struggling pulling air in? I also thought about the MAF and IAC valve being dirty? And thank you for that good info. I didn't realize it was running.

[BxKizashiS]

I was experiencing the same.. Changing your air filter to the K&N one is very helpful. Allows more air to come into the throttle.... Also when u press the brake or activate power windows the lights would dim or youll get rough idle.. thats because of our crappy low amperage alternators... SingerAlternators make high output ones for us. This will definitely eliminate for good that power draw feeling.. if you want a nice fix on a bugdet, upgrade all your lighting in your car to LEDs.

[murcod]

I have posted this before but it did not show up on here. So here's the issue. When in Drive and when the a/c is off, the Rpm's hover around 550-600 causing and annoying shake. When the a/c or the front defroster is on the Rpm's jump to 700 and it smooths out. It does none of this in reverse however. Also, on e I lift off the brake pedal to accelerate, it goes away as soon as My foot leaves the brake pedal. Anybody have this issue? I'm beginning it's yet another trait of the damned cvt or torque converter.

Just found your original post http://www.kizashiclub.com/forum/viewto ... =12&t=1358 on page 3

The engine ECU will raise the engine RPM when the A/C is switched on - or it senses any other high electrical load.

Do the CVT Kizashi's creep forward - from a standstill- if you lift your foot off the brake pedal (ie. with no accelerator input)? If they do, the engine is driving against the brakes - that could explain the rev increase when you lift off the brake. The engine load is being reduced by doing so.

As for reverse being different??? Perhaps something is programmed differently in the ECU when reverse is selected???

[Ronzuki]

Murcod may be on to something here as well with the 'creep forward' idea. Our cars do have a hill hold feature that I've totally forgotten about. Prevents roll back. I have no idea how it works (what takes control of what), but it does work...I've unconciously become acustomed to sitting at stops w/o foot on brake at times and the car not moving. If what you are experiencing is not alternator load induced idle fluctuation, then maybe there's a possibility of something going on with the hill-hold controls. I doubt very much a dirty air filter is causing the issue. That's easy enough to pull out and have a look see.

Too much unexplained ECU/software control of too many things for numerous reasons. Great when it all works as intended, frustrating to figure out when it doesn't.

[Bizzenn]

Thanks guys, lots of good info here. And yes, as long as it all works properly we forget or don't care as to how it works. As far as the hill hold, that just keeps the brakes on for a couple of seconds after you let off giving you ample time to hit the gas.

[~tc~]

I'm sure hill hold uses the brakes, but it think it's definitely something in the torque converter/ transmission, as mine will idle rough and a little low, but popping it in to neutral will eliminate the load - it smooths out and the idle comes up a touch