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MG MGF Technical - Carb Cleaner works with fuel injection!

Recently I have been having a problem with the idle speed of my VVC. When irst started it idles normally but after a drive it idles at around 1500rpm, only dropping back if I blipped the throttle or turned the engine off and restarted it. Today though it got worse and refused to idle any lower than 1500 no matter what I did.
From previous threads I believed the trouble to be dirt or gunk in the throttle body and so rather than strip it all down for a cleaning I used some carb cleaner.
It worked a treat and all is now well on the idle front!
Jason Harris

Carb cleaner (or sometimes called choke cleaner) works on the petrol deposits (and oil based from the breather) so natuarally the method of metering fuel into the engine makes no difference.

However adding injector cleaner to a full tank of fuel every 5000 miles is a good way to discourage petrol deposits building up on the injector pintle and restricting pattern, or later on, the flow.

Roger Parker


which particular injection cleaner do you recommend ?
How will my 40K miles engine benefit from it ?


Wynns and STP and many others sell fuel injection cleaners that you add to the petrol tank,As well as Roger says above they also have the property to coat the inside of metal petrol tanks and especially in winter this helps cut down on condesation forming in partally filled tanks.The condensation[water] can cause erosion at the injector pintle,the products also help in combining[mixing] the petrol and water.They also help as before in keeping fuel lines clean.
BUT are they suitable for plastic tanks?

The point is that the carb cleaner cleans out the inside of the air intake throttle body, stepper motor plates etc. which any additive added to the fuel would not affect. (Just as the carb cleaner sprayed in the air intake will not clean out the injectors!)
Since using it I have noticed a definite improvement in the throttle response and general smoothness of the engine - well worth 3.85!
Jason Harris

Jason, what product did you use, I have the same probem (it's very common I understand) but am avoiding replacing the throttle body due to a lack of energy at present?

I just used some "generic" cheap carb cleaner from a local car accessory shop, it was not a well known brand. I will look tonight when I get home to see exactly what make it was - but I would have thought that any make would work.
Incidentally, the problem has come back slightly - so another application is probably needed.
However I agree with you, that this is a much easier way of fixing the problem than dismantling the throttle body etc.
Jason H

Throttle body contamination comes from the engine crankcase via the breather hoses. If these become restricted at all through build up of deposits, or the cam cover areas to which they attach suffer the same, then the reduced bore sees an increase in gas speed and this is able to carry more 'weight'. This extra weight capacity means more liquid oil and semi solid deposits will be moved through into the throttle body and plenum chamber.

It is worth checking the two breather hoses and cam cover and cleaning them out. This can help reduce the speed at which the problem returns. If an oil change is due or appraoching then this is a good time to do so as older oil increases the problem.


Roger Parker

Many a Mk 3 escort has caught on fire for this exact reason - breather from camshaft cover gets semi blocked and forces oil into the airbox/carb - which then runs down the heater tube straight onto the exhaust manifold - ouch!!

This thread was discussed between 12/10/2001 and 22/10/2001

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