Rover 800 and 820 models with Lucas Hot wire Efi
Early Rover 820I, 820Si models use Lucas "Hotwire" Multipoint Efi, the means of adjusting the base idle speed varies according to the type of throttlebody fitted. Only one type is shown in the Haynes manual for the 800 although details of the other type are given in the Haynes manual for the Montego 2litre Efi.
Throttlebody Types:
Type (B) has an adjusting screw
regulating the flow through a butterfly by-pass passage. This located on
the same side as the idle mixture adjustment screw but are about 30mm towards
the front of the throttlebody and about 10mm lower down. An alloy plug
to discourage tampering might seal both this and the mixture adjustment
screw, this can be easily hooked out with a pointed tool such as an awl.
Note removal of these seals is not permitted by law in some countries except
by Rover dealers
Before attempting any adjustment check the connections to the water temperature sensors and the fuel temperature sensors are in good order, also check the little rubber vacuum pipe to the Ignition system ECU is clear and in good order, likewise the airfilter should be clean. Also check for vacum leaks, ignition faults such as a trcking distributer cap or a deffective plug lead..
Assuming the rest of the engine is in good order now get the car fully warmed up, to ensure with the engine idling the electric fan should be allowed cut in and cut out again.
Check the voltage of the throttle
position sensor sometimes called the TPS it is a simple carbon track potentiometer
and is located on the opposite side of the throttlebody to the accelerator
cable. it should read 0.325 volts plus or minus 0.025 volts
between earth and the centre connection.
This can be adjusted by slackening
the two Torx fasteners, which locate it on the throttlebody.
Also check it operates smoothly,
giving an even and repeatable voltage change in response to opening and
closing the throttle.
For all electrical checks on car electronic systems it is advisable to use a digital multimeter not an analogue type as the analogue type draw a higher current which may either damage a circuit or give a false low reading.
If you have suitable an instrument such as a "Gunson Gastester" to measure the CO content of the exhaust gas check that the CO emission are 1% (+ or –0.5% ) for non catalyst equipped cars in practice 1.5% is a good target for a high milage car of this type. Catalyst equipped cars should return a exhaust CO reading of less than 0.5%
Cycling the Stepper Motor
The next stage is to cycle the idle speed stepper motor to the base idle position.
Repeat steps 1 to 6 once more
Then repeat steps 1 to 4
The stepper motor should now be in the base idle position i.e. fully extended and the by-pass valve will be fully closed.
Now start the car and adjust the base idle speed to 750 RPM plus or minus 25 RPM for manual transmission cars and 725 RPM for automatics.
Note:
If you have a "Type (A)" throttlebody
turning the stop screw clockwise increases the idle speed.
If you have a "Type (B)" throttlebody
turning the volume screw anti-clockwise increases the idle speed.
Check the voltage output from the throttle position sensor and adjust again if required.
Check the CO content of the exhaust gases again, if it falls outside the specified limits reset the idle mixture and repeat procedure for setting the base idle speed.
If after carrying out this procedure the idle speed is still unsatisfactory try the following.
(1) Cleaning out the throttlebody and the small bore pipe to the airfilter.
(2) Clean and lubricate the stepper motor with "WD40" or "Redex"
(3) Check the resistance of temperature sensors.
(4) Check thermostat is operating at the correct temperature.
(5) Check for an ignition fault.
(6) Carry out a compression and/or cylinder
leakdown test.
(Note this procedure does not apply to 820e
and 820Se models fitted with single point injection or to cars fitted with
the later Rover MEMS Efi.)
Andrew W. MacFadyen B.Eng.Hon(Mechanical)
3/2/1999