A common issue among Fiat Doblo Multijet 1.3 users is the irregular fluctuation of the tachometer when the engine is cold. This problem usually disappears once the engine warms up. So, what causes this situation? Let’s take a closer look at this frequently asked question by vehicle owners and explore effective solutions together.
Cause of Tachometer Fluctuation
This irregularity in the tachometer when the engine is cold is often caused by clogging of the diesel particulate filter (DPF). The particulate filter traps harmful particles from the exhaust in diesel vehicles, allowing cleaner gas emissions to the environment. However, over time, this filter can become clogged and negatively affect the engine’s operation, especially when the engine hasn’t warmed up yet.
As the temperature rises, some of the particulate buildup burns off, so this fluctuation disappears when the engine is warm.
Suggested Solutions
There are several solutions to this problem:
1. High RPM Driving on Long Trips
One of the most effective ways for the particulate filter to clean itself is to drive the vehicle at high RPMs on long trips.
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Keeping the engine between 2500-3000 revolutions per minute and driving at a steady high speed in 4th gear helps burn off the deposits inside the filter.
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This method provides about 60% filter cleaning and significantly reduces the risk of recurrence.
2. Cleaning with Chemicals by a Mechanic
Another option is to take your vehicle to a mechanic and have the particulate filter cleaned with specialized chemicals.
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This method relieves the filter to some extent but usually only achieves about 20% effectiveness.
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If the clogging is severe or cleaning hasn’t been done regularly, this may not provide a full solution.
3. Diesel Particulate Filter Removal
The last and more radical solution is removal of the particulate filter.
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After this procedure, the vehicle operates without a particulate filter, which may improve performance.
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However, it has a significant downside: intermittent white smoke emissions from the exhaust may be observed. Additionally, increased environmental pollution may cause legal issues in some countries and during TÜVTÜRK inspections.
Conclusion
If you experience tachometer fluctuations when your Fiat Doblo Multijet 1.3 engine is cold, you likely need to clean the particulate filter. For the health and longevity of your vehicle, it is recommended to try high RPM driving on long trips first. If the problem persists, professional cleaning or, as a last resort, filter removal may be considered.
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