[Remonster]

Ever since my car was new I've had this problem, it used to only happen on really cold nights after a lot of hard driving. My 2007 328i doesn't have a temperature gauge (water like on most cars or oil like on 335is) so I can't give specifics on how warm the engine gets, but I noticed that if I drove the car hard for more than 10 minutes or so on a cold night, my throttle pedal started to act more like an on/off switch. If I pressed it as gently as I could, my throttle would go wide open which made the car insanely jerky, this would not go away until I turned the car off long enough for it to cool down to normal temperatures.

Now that I have my Injen intake with no airbox, I've noticed this happens much more frequently and in all weather conditions after 10 to 15 minutes of hard driving. I just wanted to know if anyone has experienced or heard of anything like this before and if you had any input.

My car has a Service Engine Soon light on which came on about two months after I installed the Injen intake, one dealership blamed the intake and refused to look at it and another told me they didn't know what was wrong but offered to change my MAF sensor and air pump because my SA said these were things which commonly go bad on cars with intakes. My SES light came back on the day after those parts were replaced so I'm convinced this is not caused by my intake and is a sign of something else not running right.

I think I'm going to stick the factory airbox back on and see how that affects things and take it back to the dealer to see if they can tell me what's actually causing the SES light, both of them told me it is very hard for them to diagnose the problem with an aftermarket intake installed.

[dvpouldar26]

It might not be anything wrong with your car, but how your transmission adapts to your driving style. If you drive really soft, it will short shift and shift around 2000 rpm if you drive your car easily. If you drive hard, the transmssion learnes your driving style, and will hold your shifts longer. My car shifts at around 2500 daily driving, while my brother, who drives very hard, shifts around 4500 rpm during normal driving. So if you are driving your car normally, then start driving it hard, going pass the kickdown, it will start holding your shifts later, and it will jerk during shifts because it is used to doing smooth, slow, shifts at low rpms. Thats how the steptronics are. That might be the problem if it isnt anything mechanically wrong with the car.

[Remonster]

I should have said my car has a manual transmission, it isn't shifting jerkily the actual throttle becomes insanely sensitive like an on/off switch.

Also, when I lift off the throttle it seems to open again rather than simply closing.

[noire07]

i know exactly what you're talking about. I seem to notice the exact same thing only when car is close to service (when the car starts reminding you that service is due soon). The rpms seem to jump on its own (to about 900rpms) even when its in neutral. It doesn't happen with hard driving it just seems to happen randomly. I, too, have the injen intake. I usually wait til the engine is fully warmed up (10-15 minutes of driving) and just shut off and turn it back on. This will usually make it stop.

I'm not sure whats going on either. My guess is that because service is almost due, the computer is modifying air/fuel mixture and the intakes throwing it off? This has happened a couple times, once the service is done, and light is reset, it doesn't happen until the reminder light comes on again.

[Remonster]

You bring up an interesting symptom I forgot about, the car does not idle properly when it isn't warmed up. When I first turn the car on, the RPMs fall until it almost stalls, jump to about 1,300 and repeat this process for a short while. During this, the car sounds uncharacteristically raw and noisy.

I'm not sure if this is related but this is something that only happened once I had the Injen intake installed AND the Service Engine Soon light came on.

For the record, I am no where near service.

EDIT: Oh I think I know where the confusion came from, Service Engine Soon is not the one that tells you you need an oil change soon or something, the yellow Service Engine Soon light is an indication of a BMW ECU error.

[mike-y]

my old integra had a very similar problem - very jerky when trying to gently apply the throttle, just like an on/off switch. Turned out to be a bad throttle position sensor. Don't know if that's your problem, but if the e90 has something similar, it may be worth checking out.

[Remonster]

I dug up an old thread related to the DME needing to be reprogrammed on some of our cars. I'm experiencing every one of the symptoms listed in that thread so I called my dealer and set up an appointment for Wednesday to have the car looked at with the stock intake in place. I'll let you guys know how that goes.

[Remonster]

As promised I have an update, with the stock airbox in place the dealer was able to identify a faulty fuel pump as the cause of my service engine soon light and the reason my car would act funny after being driven hard. It was replaced under warranty, I guess my Injen intake wasn't causing all these codes after all