I had a question about a weird symptom that my 2008 BMW 528i is having. When I take my foot off the gas pedal when I’m going 10-30 mph, the car seems to brake/stall momentarily. It almost feels as if the car is jerking for half a second. If I slowly let off the gas pedal this doesn’t happen. It also doesn’t happen at high mph.
My dealer said this is normal but I have never experienced this in all my time driving a Tacoma or accord. Wondering what could possibly be wrong with the car. Any input would be appreciated!
If the car literally stalls that is one thing - do your dash lights come on? (The ones that would come on if you just turned your key a couple of clicks without cranking it over).
But if its just jolts or something that can be a whole different thing. So you’ll need to clarify.
How long have you had this car? If you’ve had it a while, has it always done this? Or is it a new thing? I doubt its “normal.”
Automatic or manual transmission? What are the RPMs when this occurs?
You may be noticing the fuel injectors shutting off. This is normal. Most engines these days completely shut the fuel injectors off when you take your foot off the pedal to improve gas mileage and lower emissions. The only thing keeping the engine turning at that point is the forward momentum of the car, so it might well feel as if the engine is stalling or feels jerky. Try this: As you approach a stop light, take your foot off the gas and coast (in gear). As you slow down, you’ll reach a point where you’ll feel the car surge ahead a little. This is when the fuel injectors kick back in and start spraying fuel. It usually happens at a fairly low speed, like 5-10 mph, and it does this so the engine doesn’t completely stall as you slow to a crawl approaching the stop light.
@cigroller - The car doesn’t stop completely. It just feels like the car jerks back for an instant, as opposed to going into coast smoothly. .
@jtsanders - It’s automatic and the rpm is usually somewhere between 1000-2000RPM. The car has had this issue since I got it used 3 months ago. It’s still under original 4 year warranty, so I want to know if this is something that is correctable.
@GeorgeSanJose - I hope you’re right that this is normal. because it’s been bugging me. The BMW technician who drove with me said it’s normal, but I’m still skeptical. Also, you talked about the fuel injector. I’m just wondering why my 2003 Accord LX (4 Cyl) and 2006 Tacoma don’t do this.
My early 90’s fuel injected Toyota Corolla does this. The part where it surges in speed a little as the speed drops to 5 mph is very noticeable, but the part where the engine brakes when I take my foot off the gas doing 35 mph is pretty subtle. But I definitely notice it as sort of feeling like the car is being dragged to a stop by the engine. More noticeable that on pre-fuel injected cars I’ve driven. It may be more noticeable in higher compression cars like your BMW, since it is the engine compression that is doing the braking. That might be the explantion.
It could be something more serious I guess. One way to determine would be for you to drive another BMW and see if they do the same thing. Maybe go over to the BMW dealer this weekend and do a test drive of the same model.
I would search some BMW forums. A poorly shifting automatic transmission could do this. Or - it could be normal as speculated. You’d want to hear from other who own this exact year/model.
Could be normal or a small sensor or vaccum leak issue. A out of range sensor might not pick up the engine rpm quite right all the time. But not enough to set a code. Intake and engine temp sensors also often set the mix too lean in this situation. It is normal to lean out the engine with throttle closed, but you may have an issue that the IAC is not getting or properly responding to a stall condition. Slow IAC or near failing sensors.