Poor idle when cold and throttle position sensor change

[pa402 0]

Hi all

 

I'm after some advice as to what to try next given my limited knowledge!

 

My car has suffered from a poor idle when cold since last summer.  It's a standard 1.9 8v.  When it fires up, the revs would rise to 2k, then after 5 seconds or so, drop so that the car stalls.  If you apply the throttle during that time, you could catch it, the revs would then rise again to 2k and the sequence would repeat.  As soon as it warms up the problem would go away.  The SAD appears to be working as squeezing it would drop the revs again.  I was advised to check the Throttle position sensor (TPS) and give the throttle body a good clean.

 

So, after reading Haynes, I decided I didn't really understand how to do this and didn't want to mess around with anything.  I took the throttle body off to clean it and noticed that there was no click when manually opening the plate.  Does this mean the TPS is faulty or needs adjusting?

 

Anyhow, I had a spare throttle body, so thought I would fit that to the engine to see what happened.  This TPS did have a click.  The TPS has a different number 0 280 120 327 compared to 0 280 120 310  originally fitted.  The car fired up straight away but revs were very low and it wanted to stall.  I adjusted the little screw to get it to a nice steady idle.  I noticed however that the K&N filter seemed to be sucking in a lot more air than previously just at idle.  Gave it a run around the block and it felt sluggish accelerating.  Then was revving at 2k when I got back.  

 

So I'm after advice on what to do next before I just re-fit the original and live with the problem until I take it to someone that knows what they are doing!  

 

Cheers

Paul 

 

 

[welshpug 1,661]

you should have left the small screw as it was, use the large brass screw which is the air bypass screw.

 

the click doesnt mean it is working, you need to confirm it with a meter or test light.