Fluctuating Tachometer
Does anyone have any info about LI54.30-P-049068?
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My VIN is A271455 which, if I'm looking at it correctly, is outside of the VINs effected?
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The frequency of this problem happening has dramatically diminished almost "extirpated" since we switched to premium Shell or BP .
To make your mind ease , my car was jerking and worse than yours and tranny were stuck in either 2 or 3




For troubleshooting it, do you feel any speed change while this happens?
Have you tried to drive with transmission in manual mode, i.e. when you drive and see this rpm needle jumping pull the left side shifter paddle quickly once? This would set the gear one lower than what is in use while driving.
I'm thinking here if the transmission is shifting between two gears? It seems too high frequency for this though but if going to manual mode stops the problem then it is somehow transmission related.
For troubleshooting it, do you feel any speed change while this happens?
Have you tried to drive with transmission in manual mode, i.e. when you drive and see this rpm needle jumping pull the left side shifter paddle quickly once? This would set the gear one lower than what is in use while driving.
I'm thinking here if the transmission is shifting between two gears? It seems too high frequency for this though but if going to manual mode stops the problem then it is somehow transmission related.
-I do not feel any speed change when the fluctuations are occurring.
-I have not tried to shift into manual mode but I will try it on Monday on the way to work. Thanks for the suggestion.
I tried selecting lower gears using the paddles and the rpm's continued to fluctuate until they exceeded roughly 3,000. After the needle passed 3,000 it was smooth and no longer fluctuated. At the 3,000 rpm position the needle is at a relatively high angle whereas when it is at 1,000 rpm it is relatively flat. So it is almost as if the tach (or motor controlling the tach) has slack in it when the needle is horizontal allowing it to bounce around.
anyways, you/dealership have documentation that the problem started whilst the car was still under warranty. (referring to your post #6 last 8/13/2015 )
if that was down here, they should still be liable for repairs for free since they didnt fix it back when it was still covered under warranty. just my 2 cents.
hope you can get it fixed soon mate. best of luck!
I recently had the worst experience at MB Dealer. My car was great it had no issues at all but the check engine light came on due to putting Gas while engine was on which is weird but light went on. So I Took the car to get it checked and while being there they told me that my car needed a B service done because it reach the 60k miles. Long story short The car had the service done and now im having that same fluctuating issue. I accelerate and it needle goes up and down like wth my car never did that and now is doing it after picking it up from dealer. They told me the same they don’t know what’s causing the car to do that. I will upload a video once I drive back home work
Last edited by Rgflow; Sep 14, 2019 at 02:59 PM. Reason: Add video
I have read many other posts and I am beginning to lean towards a transmission issue, i have read somewhere this is a very common problem with these cars, i read somewhere also that it might be a bad solenoid, there's no error code or anything, I bought a very nice scanner which can read and control most of the control modules in this car and couldn't find any code related to the transmission.
It would be very nice to hear from someone else with a similar issue before I decide to drop the transmission myself and try to investigate in more detail what's going on.
Walter




The question is how fast can a motivated group connect all the dots.
Doesn't this seems like a tranny shaft sensor getting skewed by magnetized sludge or the crankshaft sensor?
Last edited by CaliBenzDriver; May 28, 2021 at 03:17 PM.




If there is no mild jerking or any mechanical feel that indeed the engine has fluctuating RPM, it could be the tacho itself fluctuating its value.
OP did not mention he felt a kind of engine "hunting" of 100 RPM , he kept mentioning only visual value of the RPM.




