Erratic idle after getting gas?

[Rat3d ///M]

Tonight after filling up at the gas station, I pulled out, and stopped in traffic. When I stopped, I noticed my idle became erratic. It would drop down to a near stall (<300RPM's, then bounce back up over 1000RPMs, and level off around 600RPM's where it usually sits, then repeat. It did this about every 1 1/2 seconds, until I drove away, then it seemed fine the rest of the ride.

This pretty much scared the shit out of me, but then I remembered the guy I bought the car from telling me that you can't top these cars off, and if you do, if you stop after leaving the gas station (i.e. at a stop light) the car will stall, but it will drive fine if you leave immediately and don't stop (i.e. getting on the highway). I assumed this had to be the issue he was talking about, seeing as I could not replicate the erratic idle.

For now, I will assume the car is fine, but I was wondering a few things:

1. I googled and this is apparently a HUGE issue with these cars. Several reports of this from one 5 page thread. Is what I am describing happened likely the cause of filling up at the gas station, or is there possibly another issue?

2. If it's just from filling up at the pump, what is the cause of this? This can't be "normal", so does this indicate that there is something wrong with the car, or is this a "characteristic of the car" and normal among most M3s?

Thanks in advance.

[BrewRifle]

You might want to have your idle control valve checked/replaced.

[thekurgan]

Some members have had the purge valve in the fuel filter/tank replaced, some have had techron work and as mentioned above, the idle control pieces.

[///M Power-Belgium]

I've 32K on it, and I never had this after getting gas .
Maybe you should try another brand like Shell V-Power and see the outcome .
When this happens all the time , than it's a question for your BMW/Dealer .

[///M Power-Belgium]

Originally Posted by BrewRifle

You might want to have your idle control valve checked/replaced.

It's only after filling her up .
When it's the idle control valve it happens frequent .

[Amirsm3]

This happened to me only once, but it went away after only the first stop.

[RD1M3]

This is a common issue. For me it's only happened once when (I assume) as you referenced, I topped off the tank to the very last drop. Check out this thread for some good info:

http://www.m3post.com/forums/showthread.php?t=953477

[TahoeM3]

This happens to me almost every time I get gas in this car. I took it to the dealership and they claimed they couldn't reproduce it...Not surprising since they are pretty useless. It still happens.

[BrewRifle]

I've never experienced this, but I never top off since it's entirely pointless and can cause more harm than good.

[nick3753]

Originally Posted by TahoeM3

This happens to me almost every time I get gas in this car. I took it to the dealership and they claimed they couldn't reproduce it...Not surprising since they are pretty useless. It still happens.

Me too. Doesn't matter which gas either. Rather embarrassing. Probably the purge valve. Might go back to the dealer down the road, but such a pain in the ass usually for nothing.

[DBH]

I've driven my M3 for 31,000 miles over four years and have never experienced this problem. I also don't force extra gas after nozzle has clicked off.

[MTM]

Originally Posted by DBH

I've driven my M3 for 31,000 miles over four years and have never experienced this problem. I also don't force extra gas after nozzle has clicked off.

Me, too. I top off every time. Never had this issue.

[kscarrol]

Had this issue, video posted in an older thread. Solved by replacing the fuel tank breather/vent valve...

[TahoeM3]

Originally Posted by nick3753

Me too. Doesn't matter which gas either. Rather embarrassing. Probably the purge valve. Might go back to the dealer down the road, but such a pain in the ass usually for nothing.

Yeah I need to get it looked at by a different, more reliable dealership...as well as the other problems. I never top it off..I just fill it up until it shuts off the first time.

[Rat3d ///M]

Thanks for all the help. The general consensus after reading every post in that 5 page thread, and reading the replies here is that it's the fuel tank breather valve that causes this.

Does anyone have any input on a DIY for the fuel tank breather valve, or any idea what the part might cost or where to source it (besides dealership)? I would like to get this fixed, but since it has only done it once and it's such a common issue, I don't see myself paying the dealership to do it. It seems simple enough and I am not about paying someone $500 to do something I can do myself for less than $100.

[Rat3d ///M]

I had another slight issue today with my idle. Got in the car this morning after it had been sitting all night (cold start). The car idled around 1200 RPMs like normal, slowly dropped down to 800 or so after about 10 to 15 seconds like normal, then stayed there where I let it idle for about 45 more seconds. Everything up to this point was normal, but I revved it up to about 1500 RPMs for a quick second, and the RPMs dropped down to 500-600 instead of where they were at 800 (like on a normal cold start). Upon dropping down to 500, the car immediately began surging between 400 and 600 RPMs, up and down, over and over, about 2 or 3 surges per second. This lasted for about 10 seconds, then stopped.

I am slightly paranoid after last night, and am not sure if maybe this was related? I know these cars are finicky on cold starts (especially on cold days like today), so is this "normal" behavior for these cars? Every little thing the car does now I think there is something wrong with it (thanks to my erratic idle last night).

[nick3753]

Originally Posted by ||||||||||

I had another slight issue today with my idle. Got in the car this morning after it had been sitting all night (cold start). The car idled around 1200 RPMs like normal, slowly dropped down to 800 or so after about 10 to 15 seconds like normal, then stayed there where I let it idle for about 45 more seconds. Everything up to this point was normal, but I revved it up to about 1500 RPMs for a quick second, and the RPMs dropped down to 500-600 instead of where they were at 800 (like on a normal cold start). Upon dropping down to 500, the car immediately began surging between 400 and 600 RPMs, up and down, over and over, about 2 or 3 surges per second. This lasted for about 10 seconds, then stopped.

I am slightly paranoid after last night, and am not sure if maybe this was related? I know these cars are finicky on cold starts (especially on cold days like today), so is this "normal" behavior for these cars? Every little thing the car does now I think there is something wrong with it (thanks to my erratic idle last night).

Take a deep breath........From what I've read a little erratic idle on cold start is common.

[fastmike]

I took my car in for oil + spark plugs and had my mechanic change the fuel tank breather valve.

I filled gas once so far and it didn't show the idle symptom. It happens about 50% of the time.

He said the part is $80 but the labor is a lot more.

Originally Posted by kscarrol

Had this issue, video posted in an older thread. Solved by replacing the fuel tank breather/vent valve...

[Fastscooter]

This has happened to me as well, I've been able to duplicate it 5-6 times in a row. The key is to fill up, drive a few blocks, sit and let it idle with the ac on full cold. I've taken it to the local dealer 3 times and the first two I got the could not replicate excuse and no codes. Third time I showed them a video of it almost stalling in my driveway. This time, they found a fault that said I needed my throttle bodies cleaned, despite the fact that all 3 times I told them I need a new purge valve. they said that warranty rules with BMW say that they need to find a fault in a part or they can't replace it. Throttle cleaning costs me $360 by the way. Im going to fill it up tomorrow and let it idle. It has nothing to do with bad gas as I've tried several different stations. If it stalls again tomorrow I'm going to lose my mind and tell my dealer I'm going to another dealer because clearly he doesn't know how to fix my car. Is there anyone on here that got the purge valve replaced under warranty and if so, how did you get them to change it?

[bronch]

I've had this happen a couple times in the last 6 mos or so, but it was not related to filling the tank. I get gas 90% of the time at the same place. It's just been random, so don't think it's a filter or anything like that and just chalked it up to ECU gremlins... Yes, I believe in gremlins.

[kscarrol]

I had this happen after filling up or with a 1/4 tank, did not matter as it seemed random. Digging through this old thread started by member gpitts is what led me to the solution...

http://www.m3post.com/forums/showthread.php?t=953477

[bronch]

Originally Posted by kscarrol

I had this happen after filling up or with a 1/4 tank, did not matter as it seemed random. Digging through this old thread started by member gpitts is what led me to the solution...

Interesting. Hasn't happened to me in a couple of months and I would think if it was fuel pump or pressure valve failing it would have gotten worse.