RPM drops on idle

[Ajolives]

Originally Posted by woody888

So, your idle will increase if you turn on AC? How about turning off? Would idle drop when you turn off AC?

Yup, like clockwork.

[woody888]

Originally Posted by Ajolives

Yup, like clockwork.

So, if Turning off AC with brake , my RPM will drop to 500-550 RPM.

Isn't it too low or should retain at 800 RPM?

[Ajolives]

Originally Posted by woody888

So, if Turning off AC with brake , my RPM will drop to 500-550 RPM.

Isn't it too low or should retain at 800 RPM?

Brakes shouldn't affect idle conceptually. Also, when I push in my clutch the idle pops up to about 700 rpm's.

I would imagine theres an extra load on the engine if it's always up at 700-800

[BRNDNSLVRA]

So for the longest time I've had this strange rough/fluctuating idle. A/C had to stay on all the time or the cars idle would drop. My car would constantly stall. Mostly in congested areas and if it's hot af outside. If I'm in Miami, it'll do it 90% of the time when Im there. I've been chasing it forever. I changed my fuel tank breather valve 2 years ago. I even tried a low mileage ICV. 2 weeks ago I changed my O2's. While that did fix things, it only lasted a day and then the car acted up again.

A friend pointed me in the direction of the fuel rail sensor. I just swapped it over and the car idles beautifully now.

Buy it here. Yes you need this kit or buy an OEM. The Bosch one is better.

I can sit with the AC off and the idle will be fine HOWEVER, if I put my foot on the brake at a light or something with the AC off, it'll start to drop and the car will shake. Foot off, it's fine. So I feel that it's definitely a vacuum leak.

I believe replacing this hose that connects to the ICV will fix things.


I'll let you know what happens. I havent been to Miami again since I replaced the sensor. Miami is where this car falls on it's face all the time. I think the heat or elevation level effects it. Idk. Maybe Im an idiot.

But if you're having the same problem. Try your fuel rail sensor.

DIY is easy. Take out airbox (remove 2x 10mm screws and loosen clamp from elbow and pull out). Then you just unplug the sensor and unscrew the old sensor. But put towels around and do it slowly. Fuel will shoot out. Keep the gas tank open while you do it to relieve pressure. Screw the new one in, connect sensor and you're off. You can reset adaptations if you have the tools to do so.

[BRNDNSLVRA]

Originally Posted by 954MM

So for the longest time I've had this strange rough/fluctuating idle. A/C had to stay on all the time or the cars idle would drop. My car would constantly stall. Mostly in congested areas and if it's hot af outside. If I'm in Miami, it'll do it 90% of the time when Im there. I've been chasing it forever. I changed my fuel tank breather valve 2 years ago. I even tried a low mileage ICV. 2 weeks ago I changed my O2's. While that did fix things, it only lasted a day and then the car acted up again.

A friend pointed me in the direction of the fuel rail sensor. I just swapped it over and the car idles beautifully now.

Buy it here. Yes you need this kit or buy an OEM. The Bosch one is better.

I can sit with the AC off and the idle will be fine HOWEVER, if I put my foot on the brake at a light or something with the AC off, it'll start to drop and the car will shake. Foot off, it's fine. So I feel that it's definitely a vacuum leak.

I believe replacing this hose that connects to the ICV will fix things.


I'll let you know what happens. I havent been to Miami again since I replaced the sensor. Miami is where this car falls on it's face all the time. I think the heat or elevation level effects it. Idk. Maybe Im an idiot.

But if you're having the same problem. Try your fuel rail sensor.

DIY is easy. Take out airbox (remove 2x 10mm screws and loosen clamp from elbow and pull out). Then you just unplug the sensor and unscrew the old sensor. But put towels around and do it slowly. Fuel will shoot out. Keep the gas tank open while you do it to relieve pressure. Screw the new one in, connect sensor and you're off. You can reset adaptations if you have the tools to do so.

Update: still having issue. Gonna replace the MAF sensor and that tube eventually.

[nah dude]

I've replaced that MAF sensor and tube quite a few times. Usually when I have brake service done. It causes a lot of issues and the issues you describe are in line with it. Over time it will get worse and start causing increase emissions and firing all kinds of weird codes. Sometimes it'll cause misfiring. The last time I had to replace it, all 8 cyl were misfiring. It's a pain in the ass, but you can just replace the sensor, no need to replace the tube. This is the sensor I used, it's the same one BMW uses but doesn't have the stamp obviously. Really annoying the amount of issues caused by a 20 dollar sensor. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Richneerd]

Originally Posted by noneedlessnoise

I've replaced that MAF sensor and tube quite a few times. Usually when I have brake service done. It causes a lot of issues and the issues you describe are in line with it. Over time it will get worse and start causing increase emissions and firing all kinds of weird codes. Sometimes it'll cause misfiring. The last time I had to replace it, all 8 cyl were misfiring. It's a pain in the ass, but you can just replace the sensor, no need to replace the tube. This is the sensor I used, it's the same one BMW uses but doesn't have the stamp obviously. Really annoying the amount of issues caused by a 20 dollar sensor. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Yup, I had this issue too, for me I just cleaned it and put it back in. Fixed and motoring on!

[nah dude]

Originally Posted by Richneerd

Yup, I had this issue too, for me I just cleaned it and put it back in. Fixed and motoring on!

Yeah, you can do this too but for the amount of time it takes to dig out that sensor I just replaced it. Pretty annoying to get to!

[Vuu]

Bumping this thread because I just started getting the same issue.

Might be replacing my MAP sensor since I pulled it to inspect.

[avantegardestyle]

BUMP,

at my wits end with this,

amount of stuff i've changed, and still having the same problem

anyone has any updates?