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My 1998 Focus 1.6LX, with 22000 miles, appears to have a variable idling speed. If the car is moving slowly, at around 5 mph, in neutral, the idling speed is about 300 rpm higher than normal. As the car comes to a rest, the idling speed returnes to normal. Is this behaviour normal? Shortly after buying this Ford Direct car, the idling speed occasionally shot up when at rest. The Ford dealer adjusted something, which appears to have cured this fault, but the above 'fault' remains.
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It might merely be the ECU adjusting the idling speed to ensure all fuel entering the combustion chambers is properly burned and that no unburned hydrocarbons reach the cat. But let's hear what other readers have to say.
HJ
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That's right. The ECU will try and stop the engine from stalling. As a result, if you drive the car at close to tickover revs, from the crank sensor and load sensor, it will think a stall is coming and try to pick them up, effectively increasing the throttle (though it does this with an air-bypass type valve). Once the revs come up, it will then drop them again. Sometimes this is hardly noticeable, sometimes not, and it can feel as though the car is running away with you. I'm not sure that anything can be adjusted, apart from driving style, as it's probably causes by a number of the myriad of sensors all working at the limits of their tolerances. The A/C cutting in may also add to the problem.
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Sorry, I answered the wrong question.
The revs will drop to the final tickover speed only when the vehicle speed drops to zero. All part of the programming to make gearchanges smoother, better economy, better pickup, and to prevent stalling which does the cat no good, as HJ said.
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In my experience this slight pick up of idle speed when in neutral when the car is moving is common to several vehicles. I'm sure the other readers are correct when they say it's programmed in to the ECU.
Regards
John
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while the car is moving forward a speed sensor on the gearbox sends a signal to the E.C.U. which raises the idle speed slightly to help make smoother gear changes during normal driving. This is a normal feature of the system.
another thing to ensure is the E.C.U. for the engine (which is reprogrameable by your local Ford dealer) has the latest level programming .
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This is normal. The higher idling speed is triggered by the car in motion. A signal from the speed sensor "tells" the ECU the car is moving and the idle speed is raised until the car stops then the engine returns to normal idle. All to do with emissions I'm afraid. Ford Vehicle Speed Sensors are notoriously unreliable and this was probably replaced by the dealer, a very quick job.
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