idle jumping when cold

[mds]

Hi i am back for more of your expert help!!

When the car is started first thing in the morning it immediately idles at around 1300rmp which i beleive to be correct.
But once you drive or blip the throttle the revs fall to around 500ish and bounce between 300 to 600 rpm they continue to do this untill the car has warmed up and then she idles reasonably well at 900-1000 rpm, there is still a little fluctuation once warm but i can live with that as it is between 900 and 1000rpm.

The car never stalls when cold but when the idle falls low for a second it feel as though it may turn off but then shoots back to around 600rpm and continues to do this bouncing up and down.

What do you guys think this could be? i thought it could be a lamba sensor fault as i have experienced something similar with my escort cosworth recently, but before ordering a lamda i thought i better all of you guys,"in the know"

thanks in advance for any help.

 

[Rage]

I have the same problem. When the engine is warm, it sounds like the engine is misfiring.

 

[Simmo]

Are you guys using standard cams and a non-flowed head?

 

[mds]

Hi my car is totally standard even down to the original little exhaust and air box
thanks for the reply

 

[Simmo]

sounds like it could be the idle control valve playing up. Anyone else confirm this or have another solution?

 

[JIMMYBACK]

when was the last time you did a full service

 

[mds]

thanks for the prompt reply!
I had an oil and filter change last week and changed the plugs on sunday , i used some bosch plugs, the ones i removed were champion and the problem was the same with those, the car pulls hard and drives fine it just does it at idle sometimes when cold and today i noticed it especially does it if turn the car back on 10 mins or so after it has been driven for a good period, it is not a constant problem just an annoying one!
Also i have also noticed first thing in the morning it idles fine untill you drive it and stop and then it fluctuates until its warm.


thanks again guys

 

[mattygti-r]

oh sounds like the problem ive just had on my GT-R

 

[mds]

Update
noticed today after car had been in car park for 5 hours so it was totally cold, that the same irregular idle i.e. between 250-600 constantly jumping up and down. I now beleive it to be when ever the weather is warm because this morning when it was cooler and for that matter when ever it is cool the car onced turned on from cold idles well, if this theory is total rubbish tell me it is just an observation.
Any thoughts????