Tickover problem on my 1988 16v

[bodga]

On the whole my car runs sweet . pulls well etc, but sometimes the tickover drops to what looks like on the tacho, 500rpm (sounds like a V8 ). if it drops when the engine isnt warmed up fully she will cut out. if i turn the ign off and start the car again she will tick over ok again. 

i have done some investigations and i have noticed that when the tickover drops the ISV is not buzzing, but i turn the ign off and on it buzzes as normal. if i disconnect the ISV plug with the ign on, then plug it  back in, it doesnt buzz

ive already removed the ISV, cleaned with degreaser, then lightly oiled the plunger inside before refitting.

ive read on the mantainance section that 2 of the temp sensors on the r/h side of the head control the ISV???

if i OHMS test them 3 temp sensors and they all give me the same reading, they should be ok

does any one know how this ISV works??? i know plunger opens and closes at a very high freq but what controls the freq? is it the ECU behind the ash tray?

sorry for loads of Qs but im not going to put my cowboy hat on just yet and adjust the tickover screw to bodge it im tempted thou

[rubjonny]

I have noticed this as well, plug in the isv with ign on and it no buzz.  mine worked fine though!  1 of the sensors is for the isv yes, its the one with the red/green wire. check your idle switch is clickign with the throttle shut every time, if the upper linkage bit is a bit sticky it wont always hit the switch, especially if you release the throttle gradually

[bodga]

Cheers rubjonny, i will test them sensors as soon as i can. the idle switch seems to be ok, if i hold the throttle open a little and operate the switch manually the engine note changes. i will clean out the intake thou too.

[bodga]

OK,  i tested the temp sensors as follows:

                              at tickover from cold @5mins

Front top                  0.566 Kohm    red/yellow

front bottom              1.68K ohm     green/red

rear                          1.032K ohm   blue/white

i swapped the front wires round so green/red wire is now on the top front sensor and went for a drive.

no problems at all, oil temp reached 90deg, again took readings:

Front top                   95 ohm    green/red

front bottom              117 ohm     red/yellow

rear                          164.6 ohm   blue/white

with the ign is turned on, ISV buzzes, if i disconnect green/red from its sensor the ISV stops.

I think its sorted now, Thanks for your help rubjonny

[edd16v]

Just wanted to bump this topic up and ask a question rather than starting a new topic.

Which colour wire should be attached to which sensor, I know that you can swap them around but just wondering how it would have left the factory??

Cheers

Edd