[Closed] Decarbonising an engine

Assuming that coking is at the root of your trouble, Forté fuel flush ([url= http://www.forteuk.co.uk/ ]link[/url]) is excellent. Either stick a whole can's worth into a 1/4 tank, or, for a really boithersome engine, directly into the injection system through a vacuum advance.

I used to run an early K-series engine which would coke up every few thousand miles due to the valve guides being designed around being used with leaded petrol (for some bizarre reason). The valves would stick in the guides with the worst-case scenario being that the engine just wouldn't turn over properly, even on a push-start.

You'll get loads of white smoke out of the exhaust, but the difference in performance will be obvious. I just noticed from the Forté site that they no longer sell to the public. I used to order mine from a Rover dealer; but perhaps an autoparts store would order in for you.

The usual sugestions on a golf gti site I used to go on were to take a very small diameter (1mm ID or so) vacuum hose and trap it in the inlet hose so that it was sucking into the engine. The get the engine warmed up fully and put the end of the narrow hose into a 1L jug of water and hold the engine at about 3k RPM until the water is sucked through. Idea being that the water is sucked through the engine in very small amounts and flashes into steam, cleaning the inside of the engine. it's the same as the cans of '10k boost' you can buy in Halfords (which costs £20 ish). The vacuum line needs to be very narrow (I think 1mm I.D. was recommended) otherwise the engine can suck the water in too fast and damage the inside of the engine.

The other recommended method was to let 1L oil out of the engine then replace with 1L of ATF fluid and run the car gently for a day or two. Apparently the ATF has loads of detergents to keep the inside of the Auto box clean and by running it in the oil it will clean the inside of the engine. After 1 or 2 days gentle running you drop the oil, flush with cheap oil then drop the oil again and fill up with decent stuff.

If you can't be arsed with either of those methods, buy a can of '10k boost' from Halfords. With the engine fully warmed up, remove the air filter from your car. With a friend holding the revs at about 3k RPM spray the whole can contents into the air filter housing (the engine will suck it through) and if it works your street should disappear in a cloud of smoke as all the crap burns out of the engine. And then change the oil

I work in a vauxhall garage and we have never decoked one of those engines. Check for air leaks or blocked breathers first.

Hmmmmmm

I may have imagined this. But I remember as a much younger man being told that half a gallon of diesel in a rank of petrol works wonders on cleaning a motor out.

But please check before you try......

Get one if those plant mister sprays, take out the air filter, rev the spuds out of it and spray lots of water into the air intake.

That should do the trick.....

To Knottie8, where would I be checking for that?

Running on after the ignition is switched off is caused by a hot spot inside the cylinder igniting the petrol without a spark.
I take it this is an old carburettor engine ?

It's very rare to get significant carbon build up with modern fuels and oils.
First and easiest step would be to have a look at the spark plugs.
Are they sooty or are they burnt white ?
Are they the correct grade ? Too hot a grade of plug can cause running on as the tip of the plug its self gets hot enough to ignite the petrol.

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half a gallon of diesel in a rank of petrol works wonders on cleaning a motor out.

The Forté stuff is available on Ebay for around a tenner and is definitely worth a try.