Ammi

Started her up this evening and I Immediately noticed rough idle/bouncing RPM needle. Every time the RPM needle dipped, my map light dimmed too. Every time the RPM needle jumped back up, map light will be bright again. Dying battery? Perhaps dying alternator?

Ammi

anyone w/ similar experience?

ECBAOBAO

Hey Ammi,

I had the same thing happen to me, but it only happened once and went away. I posted it on here but no one seemed to know..

My front small sbc battery light is on tho..so maybe its that? not sure..

The RPM needle is a little laggy when u start up right?

Ammi

Yea but battery light is not on for me though. I was hoping I could find about little more before I took the car in for service

WEC

Similar thing happened to me. Was trying to look for answers over a few days, but then an error message popped up, "Low Battery - Some convenience functions not available." These convenience functions were, among other things: Parktronic, convenience features (steering wheel/seat), D/C adapters, auto climate control... I can't think of any others.

I replaced the main battery (the one in the trunk) and thought it would help. It seemed okay for a day or two. I never got the low battery message, but randomly my stereo sound would go in and out, my headlights would flicker as well as my dome lights. Not to mention the rough idle.

I was dreading that the alternator was out. Took it to my mechanic and he found out it was the voltage regulator. Changed it out and she's been right as the rain. Hope this helps.

tarokyama

SAME PROBLEM!!!

I have been searching for weeks for a solution,
cleaning the maf sensor, cleaning throttle body....

After start needle bounces around a little and lights dim
just like you guys said.... I have a brand new battery installed too....

Where is this voltage regulator? any DYI info would be much appreciated

thank you...

TTMotorsports

Check the voltage that the alternator is producing.

Definitely electrical related and MB's really need a consistent voltage or funny things start to happen like this!

tarokyama

I checked voltage using the hidden menu
on my dash and I get a reading of about 14.3 to 14.5 volts but it rapidly
switches between the two every second or so
When I rev the engine there is no change

Is this normal?

alikadus

had the same problem a month ago . took the car to the dealer . the problem seemed to be from the alternator (its the thing that splits the power from your battery to your car) they replaced it for 440 $ without labor chargers i know !!! the problem went away and never came back .. i think it was because i was driving the car hard when it was raining ... any ways hope it helped !!!

WEC

I had it changed by a mechanic, cost me about $400 parts/labor. All he told me is that it is near the engine block so I had to leave my car with him for a few hours so that the engine could cool off before he reached in there to change it out. After changing it, the problem went away and has not returned. I would post a DIY if I could - sorry. Good luck.

cls55

the voltage regulator is in the trunk.i had that changed plus the alternator.

Don_ahmad

Helloooo
im am suffering from the rough idle on cold start too.
but i have a few questions to know if i have the same problem as you guys had.
the idle rough happens only when the engine is cold but when it reaches its normal temperature(above 80degrees) the problem is gone.
also after warming, when applying brakes to stop the car , sometimes the car shakes like if the engine is gonna shut down but it doesn't.
this shake is very clear when i am driving in reverse mode.
noting that a star scanner didn't get any error.


i already changed the MAF , the Throttles ( there is 2 throttle) , checked for air leak, and i tried another ECM but the problem is still the same.

do u think it is a voltage regulator or an alternator??
i just want to make sure in order not to pay for something anymore that will not solve my problem.can the alternator or the voltage regulator be tested somehow?
won't they give an error to the scanner or some codes?

this problem really made me hate my beloved car

thank you all