Irregular Idle Speeds

[Celsiorous]

Hi,

I have a 1990 Celsior, I have previously owned a 1991 Celsior and both of these have had some strange idle characteristics. If I drive on the motorway usually between 110-120kph for around 45 minutes then pull off and stop at a set of lights the engine is idling at around and sometimes over 1000rpm in gear almost as if the choke was on. After around 10 seconds of being stationary in gear the idle will reduce to around 650-700rpm. Also when driving in a 50kph area sometimes I notice that no throttle is necessary as the idle speed is high enough to keep the car moving at around 50 then it will drop revs and the car will engine brake, then I will throttle again and then find that throttle is not necessary again and so on and so on.
Has anyone else experienced this or have any ideas about fixing the problem or is it just a trait of the car?

Thanks

 

[Peewee]

Remove the ISCV, clean it.
Clean the throttle body.
Make sure the TPS is at IDL with the throttle plate closed.

It should fix it.

 

[Celsiorous]

Cheers Peewee, what is the ISVC? Do you mean make sure the TPS is at idle with the throttle plate closed? Sorry im new at this.

 

[Peewee]

ISCV = Idle Speed Control Valve, that black round thing at the front of the plenum.
It gets gummed up and cant operate to 100%

With the TPS, when the throttle plate is closed, one of the pins reads this, its the IDL pin.
If the throttle plate gets gummed up, it sometimes only closes 95% of the way, so IDL is never reached, and the computer doesn't switch over to the IDLE map.

Read up about testing and reseting the TPS.

 

[Roger]

Thanks Is the IAC the same as the ISCV
Roger

 

[Peewee]

IAC = Idle Air Control
ISCV = Idle Speed Control Valve

Same thing.

 

[Roger]

To pull out the tps on the celsior as described in the above link sounds very complicated. It seems a lot simpler on the soiarer i think. is it is a matter of undoing the nut that is in the centre of the unit once the cover has been removed and pulling it out or is there more to it than that. I hope i have the right part in mind. Is there a site that describes the removal operation for the soarer.

 

[Peewee]

You don't need to remove the TPS to adjust it.
Just loosen the 2 screws that bolt it on and rotate it a few degrees.