Idle control

[Phil 99]

Hi
Can someone please inform me to the location of the idle control valve on a 2.0i 1991 MG maestrol?
Many, thanks

[G51 NAV]

The throttle-potentiometer is located behind the throttle housing. The throttle housing is at the back of the engine marked “Efi” and has the stepper-motor screwed into the left of it. The throttle-pot can be adjusted by loosening the two Allen screws which hold it tight. The pot itself rarely needs adjustment unless you suspect previous tampering: what’s the symptoms? I guess you must have a problem or else you wouldn’t be asking!

[Phil 99]

Hi, thanks for that
I do have a bit of a problem, the car starts fine and runs fine, but when engine is up to temp and i have done a couple of miles, when i come to a stop the engine idle speed dies and it stalls. It restarts fine.
I notice when i dip the clutch in, it stalls aswell - although it takes a few seconds to happen. Dipping the clutch at higher speeds does the same, but it restarts automatically when i realease the clutch.

What do you think it may be? Everything else 'seems' ok.
Regards

[G Force]

Hi, This problem is More likely to be a mixture of servicing and basic settings. I would make sure there are no kinks, blockages, or leaks in the breather hoses and no vacuum leaks. Check that the air filter is clean, and the ignition system components are in good condition and spark plugs are gapped correctly. Don’t forget valve clearances affect engine performance, idle quality and emissions.

If you are having problems with erratic idle speed and stalling you should reset the base idle. I would normally recommend cleaning the throttle body out before you do this. The best way is to remove the throttle body and unscrew the stepper motor, then give it a good clean with carb cleaner to remove all the gunk that accumulates. You will probably find the small breather port needs unblocking as it is nearly always blocked.

To set the base idle the engine needs to be hot. Then you need to ensure the stepper motor is fully closed (there is a special tool for this) but you can do it by using the following method.

Turn on the ignition and wait 10 seconds then remove the stepper motor plug, then turn off the ignition and wait 30 seconds or until you hear the main relay click out. Then replace the stepper motor plug and turn on the ignition and wait 10 seconds, and then remove the stepper motor plug again. Turn off the ignition and wait 30 seconds etc. Then repeat once more this will ensure the stepper motor is fully closed. With the stepper motor plug disconnected start the engine and set the idle speed to 650rpm with the throttle stop screw. Then replace the stepper motor plug.

After setting the base idle you will need to reset the throttle potentiometer with a voltmeter to read 325mv output with the throttle closed with ignition on.

Once you have done this with engine at normal temperature set the CO to 2% with the screw on the throttle body nearest the stepper motor, that’s if you have access to a gas analyser of course.

If the engine still stalls when coming to a halt it could be a faulty road speed transducer. To test the transducer disconnect the harness plug and connect an ohm meter across the transducer wires. Then jack up one wheel and rotate the wheel observing the reading on the meter, it should fluctuate between 0 ohms & open circuit.

Regards Gary

[Phil 99]

Thanks very much. Great reply, I'll get going on this soon.