Engine cleaners / treatments

Sandspider · Mar 13, 2015

Hi all.

Just taken my 944 on a long journey. However, during the drive, she seemed to stick a bit after prolonged time at certain revs, such as motorway cruising. So if I was to accelerate from 70 to 80 to overtake let's say, there'd be a slight hesitation, even a slight drop in revs before the acceleration comes on. I was wondering if it might be an injector problem? Stopping the engine for 15 minutes returns it to normal. But she also idles a touch rough sometimes.

Anyway, I was wondering if its worth trying an injector / engine cleaner fuel additive? Or are these modern day snake oil? Or, could they even damage an engine? If they do do any good, which one do people recommend?

Thank you.

graham.webb · Mar 13, 2015

I used RedEx injector cleaner to clear a lumpy tickover when I first got my S2...it improved things and did no harm.

Don't know if it would solve your problem, but worth a try I'd think.

The other obvious comment is to avoid supermarket fuel (I expect someone will disagree with that!)...I've used Shell V Power 98 RON since the ethanol content went up in 95 RON. Recommended on older fuel systems as it's still only 5%.

Mark_Bennett · Mar 13, 2015

I remember when I had a 944 that injector cleaner was a service item.
If you don't use Shell V-Power then running a couple of tanks of that through might help things in the future.

Neil Haughey · Mar 13, 2015

Agree with all of the above, I used to use a can of Wurth fuel system treatment stuff once a year that really seemed to work. I then also tried a bottle off Forte fuel system treatment that Jon Mitchell gave me and that stuff seemed to work even better than the Wurth one. Tried all the redex type ones sold in Halfords years ago and have never been convinced that they do much TBH.

Sandspider · Mar 13, 2015

Cheers chaps.

I don't use supermarket fuel (though I have in the past with no issues) and I do treat it to a tank of high octane fuel from time to time.

I'll try some forte cleaner and see what happens...

Sandspider · Mar 13, 2015

Also, do people recommend the forte injector cleaner, or the petrol / whole fuel system stuff?

And is it.much different to putting a good squirt of carb cleaner into the air intake?

Thanks.

944Scott · Mar 13, 2015

I have used both forte injector cleaner and engine flush with good results.

timmyturtle · Mar 13, 2015

Forte stuff seems to be great, we used it at a main dealer with great results

Indi9xx · Mar 14, 2015

RedX is good at removing carbon from valves, piston ring lands etc.. It works the same way as using water mixed with acetone and fuel to effectively steam clean the inside of the engine in the same way that a blown head gasket removes carbon.

Forte and Wurth injector cleaners work as a solvent, to disolve deposits such as the build up of gum/varnish in the fuel system, as well as any tar build up on the intake valve.

Forte Gas Treatement (I think they may have changed the brand name recently) is there to remove deposits a little like red-X does, but I do not think they use water/steam as their agent, but agressive chemicals.

Forte make a big deal about how their fuel system products also lubricate items in the fuel system, such as injectors and fuel pumps, but I am not able to say how it may be doing this.

I personally have used all the above over the years and I stock the Wurth and Forte items in the workshop.

Their engine flush is also very good, I have managed to use that to decoke 944 engines suffering with moderate loss of compression buy using it directly in the bores of an engine overnight where it is suspected that the piston rings are gummed up in their grooves and no longer able to float/expand.

However, I think your description of your issue may be more likely caused by a worn out track on the airflow meter or a sticking airflow meter.

It could also be a fuel filter in need of replacement (not able to flow the increased fuel of acceloration enrichment that the ECU will try to perform when you try to overtake) or it could also be the fuel pressure regulator not adjusting properly to intake manifold pressure changes.

What are the emissions at idle? Have a local garage perform an engine exhaust emissions text at idle for CO (Carbon monoxide) and HC (Hydrocarbons) and post the results to the forum, those two readings at idle can tell you volumes about how the engine is running, not only in the two values on their own, but the two values viewed together can talk volumes about the source of a problem, even if in some cases where the engine is idling correctly.

Sandspider · Mar 14, 2015

Thanks all, especially Jon for the detailed post - very useful.

I will try a fuel cleaner, and have a go at the AFM if necessary. It has never been cleaned, nor the wiper arm adjusted, I've been putting it off as it looks fiddly and the weather is cold!

I don't have the emissions info from the last mot to hand, but I.know the co and HC readings were well in the pass zone. Someone said impressively low for the age of the car. Fuel filter was replaced a couple of years ago.