
Sticking valves issue with petrol engines
High-Pressure Direct Injection petrol systems sticking inlet valves
The Auto Assist group has seen a surge of issues with sticking inlet valves on petrol engines if you require more information click here to contact us. Firstly let’s start with how the build-up starts.

The diagram above shows how the build-up of contamination occurs resulting in poor performance, engine misfire and fault codes stored.
- Contaminated Injector
- Cylinder Pressure High
- Increased Carbon Deposits
- Increased blow passed Piston rings
- Crankcase pressure higher than normal
- Oil seepage passed valve stem oil seals
- Evaporation of base oil, oil additives leave sticky varnish on the inlet valve
- Return of EGR gas, large carbon deposits stick to the valve
- Valve stick due to contamination build-up
- Pinking/Detonation small droplets of oil on piston crown combust before firing the spark plug.
FAULT codes related to sticking valves issues with petrol engines (inlet):
- Misfire
- Oxygen Sensor Fault
- Map Sensor/ Barometric pressure circuit
- EGR flow
- Cylinder balance
Our Technicians have seen the following codes related to sticking values:
P0420 Catalyst System Low Efficiency
P0171 Fuel Trim System Lean Bank 1
P0401 Exhaust Gas Recirculation(EGR) Flow Insufficient
When you combine all of the related codes by system or component, these are the systems that are most likely to cause an emissions failure and/or running issues:
- Evaporative Emission System 24.3%
- Engine Misfire 17.3%
- Fuel Trim(Lean) 17.2%
- Catalytic Converter 16.4%
- Oxygen Sensor Related 11.1%
- Exhaust Gas Recirculation(EGR) System 8.4%
- Carbon Soot ~2lbs
- Nitrous and Sulphuric Acid ~40z
- Hydrochloric Acid ~20z
- Unburnt Petrol ~10gal
- Water Vapour ~120gal
Solution :
We recommend high-grade chemical and flushing treatments, alongside power flushing machines to cure the issues where possible in the event the build-up of carbon or other elements are unable to benefit from high-level cleaning then the only option is to replace the components. The Fuel Assist Group have all the required equipment on their fleet of vans and what’s more, they come to you. If you need further help please call our support centre on 03300100411.
Fuel Assist, established since 2009, has carried out thousands of treatments and repairs nationwide both at the roadside and at our garage network. Our aim is 100% customer satisfaction and we are committed to getting you back on the road as quickly as possible.
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