I'm experiencing rpm fluctuation in my 2015 Ford Ranger

Rpm fluctuation in my 2015 Ford Ranger: When driving at a constant speed, whether that be by using cruise control or not, I tend to have an issue with the tachometer fluctuating by roughly 100-200rpm. This can happen at 60km/h, 80km/h, 100km/h and anywhere in between on flat open roads while not towing anything. Even in town cruising between stop lights at 60km/h a small periodic fluctuation can be noticed. At first I thought it may be an electrical issue but when driving you can feel and slightly hear the car rev when the fluctuation occurs. Interestingly, when accelerating the fluctuations do not occur.

I have tried using diesel injector cleaner when filling the fuel tank to fix the issue, cleaned the air filter, cleaned the mass airflow sensor, manifold absolute pressure sensor and also cleaned the throttle body, all without making any changes to the issue. Do you have any ideas or suggestions on what may be causing this problem? And is it something to be concerned about?

Answered by CarsGuide

11 January 2024

David Morley

It's definitely worth looking into as it's not normal behaviour for the Ranger and could point to a problem that, if not fixed now, could lead to a bigger drama down the track. A scan of the entire vehicle's electronics might show up a problem with the fuel system or throttle set-up. While it's tempting to look at the engine itself as the source of the revs flaring, don't rule out the transmission, either. A faulty torque converter or even a low transmission-fluid level could be the culprit here.

Disclaimer: You acknowledge and agree that all answers are provided as a general guide only and should not be relied upon as bespoke advice. Carsguide is not liable for the accuracy of any information provided in the answers.

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