HELP!!! Fluctuating revs at low throttle problem

[e.dayanan]

Hey guys,

Been having a problem with my 2004 BMW E39 520i since January. At low throttle and low revs (1500-2000 rpm), the rpm meter shows a momentary drop in revs of about 100-200 rpm and then go back to normal again. This becomes more evident when cruising uphill. Note that it only happens between the 1500 and 2000 rpm range and when I am applying steady but light throttle. Also need to note that sometimes the rpm drop is accompanied by a shudder/vibration that seems to come from the drivetrain.

Tried everything. Service, change gearbox oil, DISA valve, VANOS seals, sensors, fuel pump. Last week gearbox failed. The torque converter jammed in the gearbox. Changed to a new halfcut gearbox but problem still there.

Forums online say its a torque converter problem, but even with a new gearbox?? I have reached my wits end, and am afraid this problem will eat this gearbox too. Hope someone can help.

 

[bmw7833]

Check the simplest one - fuel filter.

 

[e.dayanan]

BMW7833, we did check and the fuel was dirty. Came out grey colour. Changing it on Tuesday. But that small dude can cause so much trouble?

 

[jarance]

BMW7833, we did check and the fuel was dirty. Came out grey colour. Changing it on Tuesday. But that small dude can cause so much trouble?

Your house got water filter? If yes, why did you have it? and do you change the filter ot clean it.

and the answer that to your question is YES.

 

[e.dayanan]

Thanks for the confirmation Jarance. Just asking because when i ask for second opinion at optimum, they said it was a torque converter issue.

 

[Herbert]

DMann,

I have a spare re-conditioned torque converter that is suitable for your e39 520i. You can use to try it out whether it would resolved your problem.

 

[e.dayanan]

Herbert,

I would appreciate that very much. How do I get in touch with you and maybe perhaps meet, so you can have a try and see what you think is the problem as well?

 

[Herbert]

DMann,

Please check your pm.

 

[e.dayanan]

Hi guys,

Fuel filter changed, still no difference. Anyone else know what can be the issue here?

 

[Insured By Mafia]

Dmann, I'd suggest you check your air intake..from da beginning of the hoses up to the end of throttle body..even vacuum leak can cause rpm fluctuation...
may i ask, when you serviced your DISA, did you also check your ICV (Idle control valve)?
If not, try servicing that too..ICV is located rite after your DISA..too many videos in youtube..you should check it out..
if that is also not helping, try to swap a second-hand throttle body to see if that helps...

 

[e.dayanan]

Mafia,

Intake fully checked and cleaned and serviced. DISA valve changed to new, throttle body checked is good, ICV serviced and checked for any leaks. Nothing. Intake is literally showroom mint now. Problem still there.

 

[jarance]

Did you scan the car and what is the error code?

 

[bimmerE39]

replace your ignition coil.