Weird problem today...

[ptee]

Weird problem with the coupe today....I'll do my best to explain:

Drove the car this morning for about 30 minutes. No problem. Car got up to temp, etc.

Hopped back in the car after about 1.5 hours and noticed some weird behavior. I stalled it immediately when trying to take off which is not usual. After that, it seemed to take a lot more throttle input before the car would do anything. So, for example, I had to give the car a bit more throttle in order to avoid stalling every time. On the freeway, the car didn't respond as it normally does to my regular throttle inputs. In order to speed up, I had to put my foot in it quite a bit more than normal.

I got home, and a couple hours later took the car out again. This time it was fine. Parked it, had dinner, then hopped in to come home. Fine again.

Has anyone experienced this? Any other information I can provide to help diagnose?


More info:
Car has 49k miles.
It was quite rainy and wet when all day when I was noticing the weird behavior.
Just had the thermostat replaced a couple hundred miles ago due to the car taking forever to warm up (which fixed that problem).

[Bimjam96]

When was the fuel filter last changed?

[RedRedZ]

Symptoms could be VANOS related.

[ptee]

B - Not sure when the fuel filter was last replaced. I bought the car about two months ago.

R - I was thinking it might be VANOS related..but I'm fairly unfamiliar with the inner workings of the VANOS system.

More info:
Car has 49k miles.
It was quite rainy and wet when all day when I was noticing the weird behavior.
Just had the thermostat replaced a couple hundred miles ago due to the car taking forever to warm up (which fixed that problem).

[cabinum]

Had a similar problem a couple of weeks ago. Turned out to be the intake runner valve (DISA). Common problem for the pivot to break and cause the symptoms you describe. Open your hood and listen for a light chatter on the intake side (see pic).

[ptee]

Had a similar problem a couple of weeks ago. Turned out to be the intake runner valve (DISA). Common problem for the pivot to break and cause the symptoms you describe. Open your hood and listen for a light chatter on the intake side (see pic).

I tried this and didn't hear anything. Hmm. Wouldn't this also happen everytime I drive the car?

Drove it today and yesterday to and from work. No problem. Weird...

[CMM3]

Not sure what car you have but it could also be TPS "throttle position sensor" or the "throttle potentiometer" that the pedal connects to .
On the s54 there are 2 each TPS sensors along with the pot and I ended up replacing all three on my car.
They can become intermittent and are know to fail.

If you can get a code reader and read the fault codes that would most likely tell you exactly what's going on

[KickButtowski]

is your car AT ?

Before i convert my auto to manual , i had exact same problem as yours , turns out it was transmission in fail-safe mode. and when i restarted engine , there were no problems.

[ptee]

Not sure what car you have but it could also be TPS "throttle position sensor" or the "throttle potentiometer" that the pedal connects to .
On the s54 there are 2 each TPS sensors along with the pot and I ended up replacing all three on my car.
They can become intermittent and are know to fail.

If you can get a code reader and read the fault codes that would most likely tell you exactly what's going on

My car is a 2001 Z3 Coupe. I'll see if I can get (or borrow) a code reader...

- - - Updated - - -

is your car AT ?

Before i convert my auto to manual , i had exact same problem as yours , turns out it was transmission in fail-safe mode. and when i restarted engine , there were no problems.

Nope, mine is MT.

[Yellow14150]

If you want to check VANOS it's pretty easy as far as symptoms go. Search the forums and there are some great, step by step, ways to check VANOS. If I remember correctly (I replaced mine because they were bad), you will notice the VANOS issue above 4k RPM's. The engine will bog down and be generally less responsive than it would be otherwise. You will also notice a surging sensation to the engine, as opposed to smooth power delivery.

Mileage does not necessarily effect VANOS seals, they rubber seal that BMW used breaks down when exposed to oil for long periods of time. Basically it will go bad even if you have low mileage, the years will kill the VANOS.

I know when I did my seals (they are a great project if you want to get into doing your own work) I noticed a great improvement and throttle response. Way smoother power delivery and pulls stronger too.


Good luck!

[ptee]

The problem is still happening, but I've sort of found a way to manage it and found out a few more things.

The problem only happens on WARM starts. It never occurs on cold starts (I think this is key...)

If I go to start the car after already having driven it (so that it's warm), a "buzzing" noise occurs when I turn on the ignition. If I start the car like this, the buzzing noise continues throughout the duration of the drive and I have the problem I've described. If, instead, I turn the ignition off, the buzzing noise stops after 10 seconds or so. If I then turn the car on, the buzzing noise is not there and the car behaves normally (seemingly).

On Saturday, the "service Engine Soon" light came on. On Sunday, it went away.

I made a little video to hopefully describe the problem more: https://dl.dropboxusercontent.com/u/...problem_01.mp4

Coincidentally, a friend of mine at work just started having this same problem (seemingly). His car is a '99 2.8 convertible. He got a CEL, took it to Autozone, and the code said "Cam Sensor". Not sure if my problem is the same as his...

[taz99]

ptee, I just replaced the camshaft sensor on my 98 M Roadster. Mine didn't exhibit the same behavior as yours though, so yours may not be a sensor issue. My car did throw a CEL for camshaft sensor every time I cleared it until I replaced the sensor. I cleared the code 4 times in one day to see if it came back with any other codes.

The only difference I noticed in my car was a rough idle and it seemed to crank a lot longer before starting than previously. After the sensor was replaced, all is well.

Best of luck to you.

[ptee]

ptee, I just replaced the camshaft sensor on my 98 M Roadster. Mine didn't exhibit the same behavior as yours though, so yours may not be a sensor issue. My car did throw a CEL for camshaft sensor every time I cleared it until I replaced the sensor. I cleared the code 4 times in one day to see if it came back with any other codes.

The only difference I noticed in my car was a rough idle and it seemed to crank a lot longer before starting than previously. After the sensor was replaced, all is well.

Best of luck to you.

Thanks! Did you do it yourself? If so, how difficult was it? If you got a shop to do it, would you mind saying how much it was?

[Blacklane]

I don't think your car has any symptom of a bad crank or cam sensor.
I'm going to guess that the buzzing sound is a vacuum leak, possibly through the brake booster. See if it changes if you apply the brake. It could also be part of the vapor recovery system. That fits better with the warm-only symptom. There just isn't much else that can make noise before the engine starts and continue after the engine is turned off. A vacuum leak would also explain the drop in performance.
You had a check-engine light, so there might be some codes set. Getting those read could be helpful.
As mentioned earlier, many of your problems point to a bad VANOS, but that's not your primary problem right now.

[ptee]

Well, I used a friend's code reader and it came back with one code: P0340 - Camshaft Position Sensor "A" Circuit (Bank 1 or Single Sensor). Seems as if it IS the same problem as my buddies. Weird.

Doesn't really make sense to me why this would only be affected on a warm start, but who knows.

Seems like an easy thing to replace.

[taz99]

ptee, yes I replaced it myself. I got the part from ECSTuning for $99 for the genuine BMW part. I also replaced the VANOS solenoid switch O-Ring and the camshaft sensor O-ring because I had to remove both of those to replace the sensor. I ordered all the parts from ECSTuning.

Here is a link to the post describing the steps. One of the posts by PettitWC shows pictures of the parts needed to remove to get to the sensor. I did notice that the bolt holding the sensor in had some loc-tite on it. Probably because it is a high vibration area. I put a little dab on the bolt before reinstalling it.

http://forums.bimmerforums.com/forum...mshaft-Sensor)

It took me about 30 minutes start to finish to replace the sensor. I hope this helps and best of luck to you. This is the first mechanical repair I have had to do on the engine, and I must say, it was very easy and made me appreciate the engineering of this car.

[Blacklane]

Let us know how this turns out; I still think you have multiple issues. BTW: P0340 can also mean a bad VANOS on these engines.

[amancuso]

I must live in a parallel universe. Have had several M52/M52TU and M54 cars and never once had a VANOS issue.

[tohbi]

sounds like you have bees in the engine. the upside is you also have honey.

i had a car with a weak coil that only manifested when it was hot.

[Blacklane]

I must live in a parallel universe. Have had several M52/M52TU and M54 cars and never once had a VANOS issue.

I thought all of these cars experienced VANOS issues. http://www.beisansystems.com/
I can say that it's sort of like shock absorbers: you don't really notice how bad it is until you fix it, then say, "Wow, that's much better."
Of course, VANOS symptoms are only noticeable at lower RPMs. If you never use that zone, you wouldn't notice a lack of power there.

[ptee]

Thanks guys. Let's hope its not the VANOS.

I have the new cam sensor...should be installing it this week...we'll see how it goes!