Engine shutters

Tiny
EOB
  • MEMBER
  • 2002 BMW 525I
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 93,000 MILES
I have my car at the shop and no one can figure out what is wrong. When starting out from a slow roll or a complete stop, I get a stutter in performance that seems like a fuel or air flow problem. When driving at higher rates of speed no issues. It is at the dealership now and no codes are showing up to tell them what is wrong with it. They changed the fuel filter but nothing changed. Now they said that the computers need to be reset. Any thoughts?
Monday, January 5th, 2009 AT 7:53 PM

3 Replies

Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
Without more information, it is difficult to assess the issue from cyberspace. The stumble you have could be due to several factors including but not limited to bad fuel, poor spark internal, a vacuum leak, a possible programming issue or who knows, maybe a rodent got in somewhere and gnawed on the wiring. Short of replacing parts to see if it changes things.
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Tuesday, January 6th, 2009 AT 11:25 AM
Tiny
JNELSONMBF
  • MEMBER
  • 10 POSTS
I have an 2004 525i with a similar issue, prior to buying it the previous owner had gotten misfire codes for two cylinders so he took it in for 100,000 tune up where plugs were changed which fixed misfiring. I guess shortly after the car began the issue it is having now, when accelerating from low speeds or a stop sometimes I will feel like a studded or hesitation and my rpm's will bounce between 15,000 and 20.000 until I either give car more gas or let off and re- apply gas which stops it and car runs through gears just fine, it is literally just in that one spot it has an issue and it is no where near a shift point. Thinking it was also fuel or air related I added a bottle of the Chevron fuel system cleaner and it helped kind of. Now when I gave issue rather than bouncing my rpm's will almost surge up by about 700 each time until shifting, one thing I noticed was that it seems to do it more when I am getting lower than a quarter tank of gas, also sometimes when the AC is on as well it feels like it does it more and also is lacking power more with AC on but that maybe just me rather than an issue with the car. It definitely does not feel like a transmission problem and it does not do it all the time but it is often. The best way I can describe it is that it feels as if the injector is having a hard time spraying so its causing rpm's to bounce until I give more gas which would open it more or let off an reapply which may also help open it. Has anyone else had to deal with anything like this? Also, I am not throwing any codes except to change rear break pads but that is due to sensor being broken when brakes were checked before I bought it.
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Wednesday, June 6th, 2018 AT 12:55 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,288 POSTS
Yes, I have seen the MAF sensor cause this issue. What happens is the hot wire becomes contaminated which is normal for that many miles. When this happens the sensor is off which makes the engine lean but not enough to cause a check engine light. Here is a guide to help you see what you are in for and diagrams below that will help you see what it will be like on your car:

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken
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Wednesday, June 6th, 2018 AT 10:30 AM

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