by Bob Belding

Do you own a fuel injected gas vehicle that stalls on initial start up? Does it stumble on acceleration, and have poor power? Have you noticed that your fuel mileage isn’t what it once was?

If you answered ‘yes’ to any of these questions you should read what follows. If your answer is “no” then you must be maintaining your vehicle well.

For those of you that answered “yes”, I’ll bet you’ve done a minor or major tune up and didn’t really notice a difference. I’ll even wager you tried gas with a higher octane level and it still didn’t make much of a difference.

In the old days, when you did a tune up on carburetted engine you would also clean the carburetor itself, because it would have carbon build-up just past the throttle flap. You don’t have that problem any more because your car is fuel injected, right?

Wrong. Fuel injected gas engines have a throttle flap that opens and closes just like the one on the old carburetor. And just like the carb, carbon builds up just behind the throttle flap. This build up will affect the way your engine idles and will rob your car of performance.

A fairly handy do-it-yourselfer can take care of this build-up of carbon easily. First you will need a can of air intake cleaner. Not carb cleaner! You can get the cleaner at most autoparts retailers. Make sure it is oxygen sensor friendly.

You will also need an old tooth brush. Don’t ever plan on brushing your teeth with it again!

'90 Mustang 5.0
First, locate the throttle flap. If you’re not that familiar with your motor, it’s usually located on the air intake side of the throttle body, which in turn is situated between the intake manifold on top of the engine and the (usually) plastic tubing that runs from the air filter.

The photo shows the location of the throttle body on a 1990 five litre fuel injected Mustang.

Open the throttle flap with the engine off and look inside with a light. It should be pretty black looking in there. Spray the cleaner into the area that is black and scrub lightly with the toothbrush. Keep doing this until it looks nice and clean.

You should then reassemble the parts you had to remove to get at the throttle flap, and start your vehicle. You may notice it is hard to start and you might even have to step on the gas peddle. This is normal. Once your vehicle is running it may be a little rough for the first few seconds and you will also notice smoke coming from the exhaust. This is also normal.

Once your vehicle starts to idle normally it is a good idea to test drive your vehicle at highway speeds to burn the rest of the carbon out. You should notice a difference all around in the way your engine performs, although this may not take care of all your drivability problems.

I would recommend cleaning the the throttle flap every 30,000 km, and always when you’re doing a tune-up. If you have any doubts about cleaning the throttle flap yourself, then have it done by a licensed professional.

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