Runs like a dream on petrol, but the moment it switches to LPG it jerks, pulls weaker, and burns more fuel. This is one of the most common complaints we hear from drivers walking into our workshop. The good news is that most of these issues are quick to fix.
Jerking and Rough Running on LPG
This is by far the number one complaint. The car runs smoothly on petrol, but on LPG it jerks during acceleration or at idle.
Most common causes:
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Poorly calibrated gas maps. The LPG system has its own electronic maps that control how much gas goes into the engine. If they are not properly calibrated, the mixture is either too rich or too lean, and the engine jerks. This happens especially when someone has changed the spark plugs, coils, or done work on the intake without recalibrating the gas system afterwards.
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Worn LPG injectors. Gas injectors have a limited service life. When they wear out, they cannot dose the gas accurately, and the engine runs unevenly. From our experience, injectors should be serviced every 80,000-100,000 km.
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Dirty gas filter. LPG is not always clean, and the filter catches impurities. A dirty filter restricts flow and causes running problems. Replacing it is quick and cheap.
Higher Fuel Consumption on LPG
LPG should use roughly 15-20% more in litres compared to petrol, but the price per litre is about half, so you still save a significant amount. If you notice your LPG consumption is much higher than expected, something is wrong.
What we usually find:
- Poor LPG system calibration where the system is injecting too much gas
- Leaks in the gas lines or fittings
- A faulty MAP or MAF sensor feeding incorrect data to both the gas and petrol systems
Weak Pulling Power on LPG
Some power loss on LPG is normal. Gas has a lower energy content than petrol, so a 5-10% drop in power is expected. But if you feel a significant difference, the problem lies elsewhere.
Common cause: A reducer (vaporiser) that is not working properly. The reducer converts liquid LPG into gas, and if it does not heat the gas enough, the mixture entering the engine is not optimal. This is particularly noticeable in winter before the engine warms up.
Is the Problem in the Gas System or the Engine?
This is the key question. Many problems that show up on LPG actually come from the engine itself. Worn spark plugs, weak ignition coils, or vacuum leaks will show up on LPG first because the gas system is more sensitive.
Simple rule: If the car also runs a little rough on petrol (even barely noticeable), the problem is in the engine. If it runs perfectly on petrol but poorly on LPG, the problem is in the gas system.
Regular LPG Service - Prevention is Key
The LPG system needs regular servicing, just like the rest of the vehicle. That includes replacing filters, checking injectors, and recalibrating the maps. At our workshop, we handle this as part of routine maintenance for LPG vehicles.
If your car is running poorly on LPG, stop by for a check. Diagnosing the gas system is quick, and we will tell you right away what the issue is.