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MG ZR ZS ZT Technical - ZS Tickover

I've got a ZS 120+, and there seems to be some reluctance for the engine to drop back down to tickover, particularly when the aircon is running, when I'm driving slowly (<2k revs) in traffic. Then today I was up near the red line in 4th and took a long, slow gear change up to 5th. The engine speed fell to 4k and stayed there before falling slowly down.

I thought I'd noticed a hesitancy for the revs to drop on up-changes before. Is this common? Is it a warranty job?

TIA

Max
Max T

Warranty as this is a clear fault condition.

It is probably caused by either a sticking throttle, an issue that was not unusual with earlier plastic throttle bodies, but unusual with the current alloy bodies, or oil contamination expelled by the breather system has collected and congealed and is now causing the throttle not to close fully on all occasions

Problems can be encountered with the IAC valve (idle air control) but these tend to keep the rpms at around a ceiling of about 2000rpm tops. In the case of engine management problems the common cause is a coolant sensor failure which has a primary effect on system operation. Another often overlooked issue is battery condition as a failing battery often causes all sorts of spikes and problems to be experienced and logged.

Rog
Roger Parker

Thanks Roger - looks like a trip to the dealers is called for. Couple of other niggles too - think there's a front brake grabbing slightly.

Max
Max T

Sticky pad.

One advantage of cars that have their underpinings around for a long time and when there is well over a million other examples is that niggles and problems tend to show up.

On R200/400 and subsequent models to date where the brakes do not get heavy use there is sometimes a tendency for one pad to stick. The usual symptom is a slight initial pull to one side that is a sign that one of the pads on that side is dragging and pre-warming the disc so that on brake application that disc and one pad are already at a higher temp so they are more efficient and the brakes pull or grab to that side.

Rog
Roger Parker

See - you're too light on the brakes ;-)
David S

David - but heavy on tyres, the corollary of not braking so much for corners is that I go round them faster than my co-driver ;-)

Thanks Rog, it felt like a sticky pad. The sort of thing I'd do without thinking on the old Monty T.

BTW I'm on my first tank of Optimax and the signs are that the tickover problem is not occurring at the moment. Will keep it monitored to see if coincidence or a cure. But at 90p per litre - phew, it better be good!

Max

Max T

I always use Optimax in my ZS120+ and I find it very very good. If you want expensive try the Q8 Garage near Waterbreach, Cambs. I used that for a bit - cost about 97p at the time. I thought sod this and now go into Cambridge to get Optimax and have done for ages now - a little further but while Q8 was 97, Optimax was about 84. I will never use Q8 again.

Back of the net.
Demon

This thread was discussed between 13/11/2004 and 10/12/2004

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