What is Fuel injection cleaning

[LostKiwi]

Generally the injectors are good for life in indirect injection petrol engines due to much lower operating pressure compared to direct injection.
If you have an issue it can be found quickly by looking at fuel trims using diagnostics but in general if there's an issue you'll either get a misfire or engine management light.
A misfire will also often trip an engine management light.

The way the system works is as follows and was introduced in 1993 when catalytic converters were made compulsory.
On startup the ECU will see the coolant temperature is low so will start in open loop mode, i.e it won't use the readings from lambda sensors in the exhaust to refine mixture.
Once there is some heat in the system the ECU will switch to closed loop. The lambda sensors in the exhaust now monitor the exhaust emissions and feed back the information to the ECU. If the mixture is rich (too much fuel) the ECU will reduce the amount injected. If the mixture is too lean (not enough fuel) the ECU reduces the amount injected.
If an injector is faulty the ECU can't control the fuel properly so will turn on the engine management light. Internally the ECU also maintains an adaptive map of how far it has to adjust fuel from what it expects to what it had to adjust. It does this for long term and short term periods. These are called the long and short term fuel trims and if they also exceed certain values will cause the engine management light to be lit.
This is for petrol engines not diesels.

So as you can see if there is no management light and the fuel trims are ok (early warning will be fuel trims) then there is no need to do anything.
Modern fuels also contain additives designed to clean injectors. You can add cleaners for the injectors if you want but they aren't needed.

 

[Botus]

are we saying I'm wrong.... does terraclean not somehow pump stuff though the air intake and help clean up the ports and valves. I thought that was most of the magic ?

Can't say how it might help on the inlet side, but Alex thought water injection to inlet manifold post air filter, would clean things up. He was saying the act of heat boiling the water droplets means a mini explosion blasts everything clean. And indeed this is what happens in the combustion chamber where it has a small head gasket leak. By using a water Methanol 50 50 mix should be even better. Of course one might have issues with Methanol being nasty and hating ordinary rubber, so possible gaskets or O rings and anything plastic in the manifold might have an issue.... And then might get physical debris snag a valve unlikely, more likely to cause CATs / DPFs fun if not hot enough and or debris too big. I did do it on my father's e280CDI and a year on nothing's complaining. Pumped about 2 litres through over 15 mins.

 

[Botus]

I don't agree entirely with all the other bits above.... if you use cheap fuels with low quality or no additives, it won't be as heathy for the fuel system or the engine internals as buying the posh brands. Varnish and some combustion deposits will form in places where you don't want it and better fuels make this less likely.

A higher than normal concentration of premium additives (adding at the correct ratio to the tank) should get a small spring clean to the injectors and may help inside the combustion chamber and for the CAT / DPF. But nothing you buy to put in the fuel tank can clean up blocked inlet ports (and if direct injection) it won't help remove crud on the inlet valves either.

Mate at work drives dead slow, in an old abused fossil, scraped though MOT with dodgy emissions... Next year did terraclean and 2 bottles of cataclean (which gets good reviews) and the garage couldn't believe the difference. MOT a year on coming up this week, I'll ask how it goes and report back

 

[John77]

I think you are going round in circles buddy , you don’t have an injector problem , stop worrying about it all .
Chuck an injector cleaner in every few months for a few quid (or not) and enjoy the fact the car is working , something else is going to break soon enough on a 2005 car to take your mind off your perfectly working injectors soon enough .

Thank you. not worrying, just checking. The 5 MB's that I have had have been very reliable and rarely gone wrong apart from the occational minor problem. I will put in some cleaner and leave it at that. Thank you again.

 

[LostKiwi]

Terraclean uses a fuel replacement to do it's cleaning so cannot touch the inlet tract upstream of the injectors (it says this on their site).
There's a lot of pseudo science on their site too which always sets alarm bells ringing for me.

Water injection definitely cleans well and is very well understood and has been in use since prior to WW2 however cannot clean the actual injectors.