Fixing GDI problems ‘Where there’s muck, there’s brass’

While this northern English saying highlights that dirty tasks are lucrative, Rob Marshall finds it applicable to preventing and solving GDI coking issues, particularly when combined with a dash of knowledge and a shot of JLM Lubricant’s chemical know-how. 

Conflicting decisions are made in the name of environmentalism. GDI technology is a case in point, which became popularised as Europe particularly developed an obsession with tailpipe carbon dioxide emissions. In many ways, GDI achieved the political aim. Adding a high-pressure fuel injection system and placing the injectors directly within the combustion chambers reduced greenhouse gas outputs and made the engine more efficient than those fitted with the previous port (or indirect) injection technology. 

Yet, there were downsides. The main (often forgotten) issue was that the engines became dirtier. They also became more polluting. Conservative estimates state that cancer-causing particulates increased by over 1,000 times on GDIs, because the petrol/air mixture is not mixed thoroughly within the air intake, as was the situation beforehand. In Europe, at least, reduced CO2 emissions were being prioritised at the expense of air quality; as made evident by the original Euro VI particulate limits for petrol engines being raised to match diesels. Over twenty years since GDI became popular, the situation is only now being addressed, with gasoline particulate filters (GPF) appearing on some models. 

Getting down and dirty 

The situation becomes even worse as the car ages. The sooty exhaust gases are admitted into the air intake by the exhaust gas recirculation (EGR) valve. While this situation would not cause a problem usually, the air intake’s internal surfaces tend to be oily, thanks to the positive crankcase ventilation system. These situations cause a perfect storm, because particulates from the exhaust gases stick to the oily tract instead of passing through it. Over time, the contamination builds to such an extent that the intake becomes restricted, strangling the engine of air. To complicate matters further, the high heat levels (especially with turbocharged GDIs) bake the accumulations into a stubborn, rubbery deposit. 

The fuel injectors face a different set of challenges. Not helped by their finer tolerances, their relocation means that they face the full force of the combustion process, instead of being protected by the intake valve. Further complications include increased levels of ethanol in petrol, as well as stop-start technology, both of which can promote deposits that affect the delicate spray pattern adversely. As GDI fuel injectors cannot be remanufactured currently, taking preventative measures against deposit accumulations is a primary recommendation that any responsible garage should make to its customers during routine servicing visits. 

The winning combination 

Based in Larbert, Scotland, Ewan Lawson Motors is a garage that believes in precautionary action to prevent GDI contamination from becoming an expensive problem. Its proprietor, Barry Lawson, tells JLM Drive that: 

“As we use JLM products during routine servicing, we find that our regular customers rarely return with engine running problems. On GDI cars, JLM GDI fuel system cleaner will be used automatically during servicing, along with JLM’s engine oil flush.” 

Yet, when presented with a poorly-running GDI engine, Mr Lawson emphasises the importance of fast, efficient diagnostics: 

“Firstly, we scan for typical fault codes that we expect to see with misfires, such as P0300, P0301, P0302, P0303, P0304 and those relating to fuel mixture, including P0171 and P0172. When conducting live diagnostics, we also examine the injector opening times closely. Should an injector be contaminated, its opening time increases to deliver more fuel. Checking the short and long-term fuel trims, allied with the misfire counter, lets you narrow the diagnosis to a particular cylinder.” 

Mr Lawson also advises fellow professionals that checking for elevated oil levels, caused by fuel contamination, is not an operation reserved just for diesels. He reports that, should the injectors be blocked even partially, petrol can drip from them after the engine is switched off, which washes down the bores and into the sump. 

Clearly, such faults undermine the whole efficiency, reliability and CO2-reducing credentials of the GDI engine. Furthermore, fuel injector contamination also increases the already high levels of sooty exhaust gases, which accelerate the rate of intake deposit build, making the situation even worse. Unfortunately, the only real solution is dismounting the inlet manifold to remove the deposits mechanically. Yet, JLM Lubricants can still assist with this operation. Our EGR cleaner can treat the exhaust gas recirculation system after the manifold and cylinder head tracts have been cleaned manually. Furthermore, the JLM GDI injector cleaner is formulated to tackle the deposits that afflict GDI injectors and the chemical formulation is not too aggressive to harm them internally. 

While a garage can profit from the labour fees involved with such extensive dismantling, it commits the business to purchasing, maintaining, storing and running expensive equipment. As Ewan Lawson Motors testifies, prevention is better than cure but this need not sacrifice profitability, as Barry Lawson advises: 

“We emphasise to customers the importance of not just having the car serviced regularly but we also supply them with cans of GDI cleaner, so they can dose it to the fuel every three months. The aim is to get the customer to spend a relatively small sum with you every quarter, which helps to maintain loyalty, rather than hitting them with a large repair bill later on.”