Common Issues & Carbon Cleaning Solutions

01. Mechanical Problems

Carbon Cleaning is not a repair service. If your car has existing mechanical faults, carbon removal will not fix them. However, where carbon deposits are causing poor running, cleaning can help. Removing carbon build-up gives the engine a better chance of running smoothly, but it will not solve unrelated mechanical issues.

02. Electrical Problems

Carbon build-up can affect sensitive sensors around the engine, leading to electrical problems. Carbon Cleaning may help by removing deposits from sensors in and around the engine and exhaust system.
⚠️ Please note: this is not guaranteed.

03. EGR Valve Repairs

A common question is: Can Carbon Cleaning unblock an EGR valve?
The honest answer: Maybe.

When we carbon clean, hotter exhaust gases are recycled through the EGR valve, which can reduce some of the carbon crud that has built up over time. The best way to reduce EGR problems is to have a Carbon Clean every 10,000 miles or 12 months, ideally alongside your annual oil service.

04. DPF Filters

Blocked DPF filters can often be regenerated (cleaned) by us – provided they haven’t exceeded their service limits. If regeneration is possible, we carry it out for just £75 extra.

But the more important question is: Why are DPFs blocking in the first place?

• Often it’s because the engine valves don’t close properly,

• This leads to high emissions, and

• Sticky, unburnt fuel causes ash to cling inside the DPF.

A regeneration will temporarily fix the problem, but unless the underlying cause is addressed, it will return. Carbon Cleaning targets the root cause, and for extra protection, a DPF fuel line cleaner can be used. We carry these on our vans for only £20.

05. VNT Turbos

Since the late 1990s, many diesel vehicles have been fitted with Variable Geometry Turbos (VNT) or Variable Nozzle Turbines. These systems reduce turbo lag and provide more torque at lower revs.

They work by adjusting small vanes around the turbine wheel:

• At low revs – vanes close, forcing exhaust gases faster onto the turbine.

• At high revs – vanes open, slowing gases and preventing over-boost.

⚠️ Problem: These vanes are very prone to carbon build-up. If the mechanism sticks, it may cause:

• No boost or too much boost

• Black smoke under acceleration

• Engine going into “limp-home” safety mode

In the past, the only solution was replacing the turbo. But today, Carbon Doctor has the correct equipment to clean and restore the VNT mechanism without removing the turbo unit – saving you from costly replacements.

06. Emissions Repairs

A Carbon Clean can significantly reduce harmful emissions and may also help vehicles meet MOT emission test standards.