mk2 16v idle screw

[Diluxe]

Guys,

is this right ? when my idle screw is all the way in the car should turn off?

then why is it on mine when i pull the idle screw all the way out the car wont start, and with it wound all the way in the car is ok?

i'm tryingto get to the bottom of a lumpy idle problem............................................

cheers

[jezza16v]

You have to disconnect the ISV before you fiddle with the idle screw. If you keep screwing it in the ISV compensates and tries to keep the revs at about 1000. If you take the screw out the air gets into the hole ummetered so does not lift the flap on the metering head. What year is your car? The idle will never be perfect in an old car as there is always some slop in the cam chain and dizzy drive. Check also for air leaks in the intake pipes and vacuum feeds, there's plenty of places it can leak. Also make sure you set the idle speed up when its well warmed up, usually just after the rad fan has switched off.    Try also squirting some carb cleaner into the idle screw hole, the air feed holes in mine were almost completely blocked with oily smeg so screwing it in and out made no difference at all!

[Diluxe]

right, today i checked for vacuum leaks couldn't find any, let the car warm up then pulled off ISV but car stalled, and wouldnt idle without, so couldnt set the idle withit disconnected, however advanced the dizzy a bit and can now adjust the idle using the screw  to increase revs with the ISV disconnected, does this mean my timing/co2 was initially out?

any ideas

cheers

[jezza16v]

  Am I understanding you correctly? By 'disconnect the ISV', I meant in the 'electrical' sense, not by pulling the pipe off. If you pull the pipe off it stalls as you say because you break the intake vacuum. You can disconnect the ISV electrically by pulling the plug off the back of it or even easier, there is a plastic connector by the coil with the red wires. The timing must be set to 6deg BTDC at 1000rpm before you make any adjustments at all or you are wasting your time, if you advance it beyond this you risk 'pinking' and damaging the valves. Your CO/timing was not necessarily out although some people do retard the timing in an attempt to run on 95RON fuel. The 16v ECU is not very clever, it adjusts all the timing based on the 6deg BTDC @ 1000rpm, temperature & vacuum, it has no knock sensor so cannot compensate for any error in the idle timing set up.  Come back if you are still stuck.

[Diluxe]

yep i pulled the electrical connector off the isv and car died (all done at warm up temp), tied the same on a mates 16v same age as mine 1988, and with the isv disconnected and the idle screw pulled out the car continued to idle at about 400 rpm but it still stayed idling which is more then mine did.

so we advanced the dizzy abit, car felt much stronger on the road, dont notice any pinking..........

however i can now adjust the idle with the isv unplugged, but still not to the same degree my mate can, e.g screw all the way or out to the point just before it pops out fully = about 200 rpm change up or down round the 900 rpm mark,

on my mates, car will stall with screw all the way in and rise to about 1800 rpm with screw nearly out.

all very weird

[jezza16v]

Sounds like you need to clean out the throttle body, you'd be surprised how much c**p gets in to the butterfly flaps, it stops them shutting off properly so air leaks past bypassing the idle screw. When I disconnect my isv, the revs rise for a second then settle back to 1000. I'm not sure if that is right but the car runs fine and passed the MOT emissions test Also on the plastic pipe just before the throttle body on the underneath where you can't see them are two vacuum pipe connections, check they have not fallen off. I never knew they existed until I took the inlet manifold off to sort the rocker cover.

[Diluxe]

Cheers Jezza

[Gambit]

sounds more like your injector seals are knackered. that will also cause the idlle screw to have very little effect on the actual idle speed of the car!

easy test is to spray WD40 down each injector guide with the engine running, if the engine note changes the seals need replaced