Inconsistent Idle

[E92_TYLER]

I take my previous comment back, if the A/c is off it will do it all the time when the engine is warm. A/c on it is fine. No idea what the issue is.

[spazzyfry123]

Originally Posted by BOOF-M3

What did you figure out Tyler? Fuel tank breather valve or idle control valve? I'm getting this once in a blue on the E93 but it will actually stall. It's very rare that it does not stall if it jumps. And it will typically bounce over 1,000 rpms and then drop to zero.

Ran a smoke test on the car to help diagnose. The fuel tank vent under the intake is the culprit. Waiting to replace for right now until I decide if I should go ahead and change out the throttle body actuators while I'm in there.

Link in TurboPR 's post below for those that are having a similar situation.

Originally Posted by TurboPR

Fuel tank breather

http://www.m3post.com/forums/showthread.php?t=1273927

Originally Posted by HerbNRacer

This is a big clue as to where your problem is coming from, the Evap system acting up will cause the exact problem you described. Sounds like a vent valve for sure...

+1 for TurboPR

[mdm9]

Originally Posted by spazzyfry123

Ran a smoke test on the car to help diagnose. The fuel tank vent under the intake is the culprit. Waiting to replace for right now until I decide if I should go ahead and change out the throttle body actuators while I'm in there.

What did you do for a smoke test? Blow smoke at the air filter?

[spazzyfry123]

Originally Posted by mdm9

What did you do for a smoke test? Blow smoke at the air filter?

I didn't do it personally. The car was in the shop for some other work and just tagged this test on to it. But it's for the evap system, so you should connect it to a vacuum line as I understand it. Search around on YouTube if you want to see some videos.

[eatsleepboost]

I have not done this test on a BMW but on GM products.

There is a threaded green cap on the evap line that could be located under the hood or under the car. This line is what seals in and releases fumes from your fuel. There is a few components to the system such as a purge valve that is on the engine that uses engine vacuum, a charcoal canister, vent valve and the gas cap is part of the system. This is why you can get a check engine light if you leave your gas cap off as the system is no longer sealed.

The smoke test uses a tank of nitrogen or a machine that uses an oil and heats it up then pumps that smoky air. This smoky air under pressure is hooked up to where that green cap is that has a Schrader valve. The smoke then fills the evap lines and charcoal canister. You search with your light for any escaping smoke. There should be none as the system is intended to be sealed.

A bit hard to explain through text but no you don't simply blow smoke at the car. You put it into a sealed system and it allows you to find leaks. Without the smoke you won't be able to see regular air escaping.

[notouching]

Hey guys, my symptoms are different from OP's, but still fit under "inconsistent idle" description, so I didn't want to start a new thread.

In my case, the car either idles at ~750RPM or at ~550RPM. I believe it should always idle at 500-550 when warmed up. This is with AC off. Most of the time I have high idle. I think it drops to normal ~550RPM if I have driven on the highway for some time. I've also seen it get back to normal after filling the gas tank full.

Is this anything to worry about? I don't see any suspicious codes and the RPMs are not moving/bouncing at lights, I'm just concerned that I have high idle.

I am thinking about replacing the fuel breather valve since it's not an expensive part.

[E92_TYLER]

Ive had the issue since i bought the car in November and cant seem to figure it out. I replaced the fuel tank breather last night and it still seems to do it.

[spazzyfry123]

Originally Posted by E92_TYLER

Ive had the issue since i bought the car in November and cant seem to figure it out. I replaced the fuel tank breather last night and it still seems to do it.

Do you have a CEL?

[E92_TYLER]

Originally Posted by spazzyfry123

Do you have a CEL?

Negative, no faults pending or stored.

[R3dliner]

I don't know if this has any correlation but I've had one instance this happened after a fill up. Tested the fuel and it had almost 20% ethanol.

[spazzyfry123]

Originally Posted by E92_TYLER

Negative, no faults pending or stored.

Weird. That sounds just like a fuel tank breather issue.

[E92_TYLER]

Originally Posted by R3dliner

I don't know if this has any correlation but I've had one instance this happened after a fill up. Tested the fuel and it had almost 20% ethanol.

Yea ive gotten gas at many different locations to eliminate that issue. Buddy has the same car and his doesnt do it at all.

Originally Posted by spazzyfry123

Weird. That sounds just like a fuel tank breather issue.

Exactly why i changed it lol very frustrating

[E92_TYLER]

Just throwing rocks here to see if anyone has heard of any solutions?
Idles at rough 500~rpm when stopped with foot on the brake, when brake is released idle goes to normal. No fault codes, replaced TA's and fuel tank breather.

[msan]

Originally Posted by E92_TYLER

Just throwing rocks here to see if anyone has heard of any solutions?
Idles at rough 500~rpm when stopped with foot on the brake, when brake is released idle goes to normal. No fault codes, replaced TA's and fuel tank breather.

I'd guess your motor mounts a need to be replaced

[E92_TYLER]

Originally Posted by msan

I'd guess your motor mounts a need to be replaced

Why would mounts cause a lower than normal idle?

[msan]

Originally Posted by E92_TYLER

Why would mounts cause a lower than normal idle?

Sorry I saw "rough".

[Ram3n]

I have this problem. Replaced the ICV for jumpy Rough idle. This is my second time around for a low idle issue . The first time my Indy “ adjusted the rpm “ with his computer ( 2016) . All was fine until 4 days ago. I replaced throttle actuators and the Valve cover gaskets. After the job was done I had gotten the low idle again after the cold start finished. Before the actuator valve cover change my car idled at 750 all day at a stop or at N. After I experienced this I went a head and changed the spark plugs and the breather valve. I did all this maintenance and ended up with a low RPM idle again. It now sits at 550 rpm which Is NOT Normal. I’m going to bring back to this shop called BMW Excluservice in Rockville Md since they handled this issue the last time. No car should be vibrating and have low idle issues.

[Ram3n]

Had anyone solved this yet on their own????

[wfdeacon88]

Originally Posted by Ram3n

I have this problem. Replaced the ICV for jumpy Rough idle. This is my second time around for a low idle issue . The first time my Indy “ adjusted the rpm “ with his computer ( 2016) . All was fine until 4 days ago. I replaced throttle actuators and the Valve cover gaskets. After the job was done I had gotten the low idle again after the cold start finished. Before the actuator valve cover change my car idled at 750 all day at a stop or at N. After I experienced this I went a head and changed the spark plugs and the breather valve. I did all this maintenance and ended up with a low RPM idle again. It now sits at 550 rpm which Is NOT Normal. I’m going to bring back to this shop called BMW Excluservice in Rockville Md since they handled this issue the last time. No car should be vibrating and have low idle issues.

What is normal if 550 isn't? I assumed 550 but stable was normal without AC blowing...

As far as things to check, get them to check the alternator.

[KingofKingz]

If your battery is charged all the way up and you put your foot on the brake pedal the rpms are supposed to go down to around 550 when stationary. Let go off the brake and the rpms are going up to around 750. This is absolutely normal behaviour and has something to do with emissions.

[Ram3n]

Originally Posted by wfdeacon88

What is normal if 550 isn't? I assumed 550 but stable was normal without AC blowing...

As far as things to check, get them to check the alternator.

Thank you for your help