Total MX-5 – July 2019

temperature. As your fuel
consumption is high I think this
is the likely cause of your
problem as the ECU will keep
the cold start settings on for
longer with a cold engine.
To check, remove the radiator
cap (engine cold) and run the
engine. You shouldn’t see much
water movement in the radiator
as you rev the engine. After a
few minutes the engine should
heat up and the thermostat
should open. At this point the
top hose and radiator start to
get hot and you will see coolant
rushing through the radiator.
If water flows through the
radiator immediately from cold
replace the thermostat and a
good heater operation should
resume. The mounting nuts are
often seized and may require
careful persuasion using heat
and something such as WD-40
on the threads to free them.

[ Q&A ]

Summer 2019 | TOTAL MX-5 |^77

Tired thermostats can get stuck

open, leading to a reduction in

heater performance and also

increasing your fuel consumption

Apparently faulty electric window

switches can be brought back to

life by scraping burnt residue off

their brass terminals: removing

them from a mk1 is a

comparatively simple operation

UPWARDLY MOBILE

Q

The driver’s side electric

window on my mk1 Eunos

has lowered but won’t come up

again. I’ve checked and can’t see

any blown fuses. Any idea what

the problem may be?

A

We see this quite often. It’s

usually a faulty window

switch: luckily you can normally

repair it. Remove the centre

console by undoing the screws

in the storage box and either

side of the centre console, then

unplug the wiring harness and

unscrew the gearknob. You can

then remove the window

switches from the console.

Carefully prise the back off

the switch. More often than not

the brass terminals will be

burnt. Cleaning these with some

emery paper will get the switch

working again. If you find a

melted mess I would

recommend a new or good used

replacement is obtained.

Unfortunately this task is not as

easy on mk2s as micro-switches

are used and the plastic

actuators tend to break so that

the switch isn’t operated when

you move the lever.

BACKING UP BLUES

Q

When I reverse my car, it

judders and vibrates badly.

It seems OK going forwards.

What could be causing this

please? It’s a mk2 1.8.

A

This is a problem you only

really find on mk2s. Strange,

as it’s the same clutch fitted to

mk1s. I can only guess that the

slightly heavier car puts more

strain on the friction plate

damper springs causing

snatching, hence the surging you

feel when reversing.

However, it’s good practice

to inspect the condition of the

engine mountings to check for

excess movement. If no other

problems can be seen then I’m

afraid a new good quality clutch

assembly should be fitted to

overcome the problem. Be

sure to mark the mounting

position of the powerplant

frame where it bolts to the

gearbox so that it goes back in

the same place, or you may

induce the gearbox rustle these

cars often suffer from.

TICKOVER TROUBLES

Q

: I have an early mk1 1.8

with a very fast tickover:

otherwise the car runs well.

What’s wrong?

A

This customer came to the

garage to see us. The first

thing we did was check for air

leaks in the induction system.

With the engine running you

can spray brake cleaner or

similar around the inlet

manifold gasket, fuel injector

seals and vacuum pipes. If the

engine revs change while doing

this, you have an air leak. This

can raise the idle speed and the

offending gasket or seal must be

replaced.

If this reveals no problems,

check that the throttle

butterfly is closing to its stop

and that the idle screw has not

been opened too far (look in a

workshop manual for basic

settings). On this car you could

wind the idle screw fully shut

and still the revs were at around

1200rpm.

Next we looked at the idle

control valve. You can disable

this valve by bridging the GND

and TEN terminals in the

diagnostic box. Doing this

should drop the tickover

significantly. If not, the idle

solenoid mounted under the

throttle body may not be

working.

Remove it and try powering

the solenoid with 12 volts

briefly; it should make a clicking

sound when you power it. In the

case of this car it was faulty. A

good secondhand replacement

immediately cured the problem.

A fast tickover on a mk1 1.8 was eventually traced to a faulty idle solenoid

on the underside of the throttle body. A replacement cured the problem

Juddering in reverse is a problem suffered only by mk2s, and is probably

a sign the clutch needs replacing, though do check engine mounts, too