bad idle

Hi Lads,looking for advise please,The engine idle in my 98sti drops way down when stopping at junctions etc. After a few seconds the idle is perfect. The check engine light comes on from time to time and when i plugged it in it showed up 2 faults.....1-speedo sensor and 2-unknown fault. Fitted new speedo snsr thinking it was throwing out the stepper motor but it made no change. Fitted new air flow meter yesterday but still the same.This is driveing me nuts Been doing this since i bought it a while back and it was standard then.any ideas lads?

Maybe give the idle control valve a clean
worth a shot

possible lambda?

Yeah had a similar prob with my 99 turbo - its throttle body was full of gunk.

Mechanic gave it a spray with a xylene thinners and it did the job.

Cheers, P.

@briancollins-Sounds familiar doesnt it? I reckon lambda on way out too.

Thanks lads,it only passed nct few weeks ago and lambda seemed ok but i suppose it could have intermitent fault.Il check it out and let ye know what sorts it

cleaned idle air control valve,didnt make any difference so i adjusted it up a little with engine running raising the idle up to 950rpm.took it for a drive and now when i come to a stop its ok.idle isnt dropping down.its staying slightly high but id prefer that then cutting out.Engine light still coming on and when it does it seems to have missfire for a while until light goes out.Im thinking problem with coil maybe? I plugged in different diagnostic scanner to what i normally use and it brought up coolant temp sensor as a fault so must order one tommorow.

Sounds like the coil pack to me.

Ya thats what i was thinking alright.will prob put new coolant temp sensor in aswell.wonder how much coil pack is?