Idiots question: CO and Idle adjustment on 8v digi

[cняis]

Hi!

Am i right in thinking that the screw on the front of my throttle body (brassy coloured) is purely the idle screw or does this adjust the CO too?

I ask this because after my (useless) garage tried setting my car up properly, it was idling too high (1000-1200 rpm when warm). i adjusted this screw so it sits at about 850 rpm, but my MPG has increased from average 34 to 42 over the 5 mile trip to work! 

Anyway it seem to run a bit smoother so im happy 

[dubslug]

i believe the screw ur on abt is just idle

[DarnPB]

The idle adjustment screw is a recessed screw on the throttle body. You need a very small screw driver to adjust it. If you have used a spanner and screw driver to adjust what you thought was the idle screw, then you got it wrong and thrown out the throttle stop and microswitch setting. The CO is adjusted on the Mas Air Flow (MAF) sensor on your air box.
There is a thread in the maintenance section on how to set this lot up. Print it out and go to a noteworthy garage and say, ¨do this please!!!¨¨

[cняis]

i adjusted the recessed screw, so all's ok - no worry of "throwing out the throttle stop and microswitch setting" 

its just odd that after adjusting the idle, the car now returns better MPG... 

[DarnPB]

Sounds as if the ´useless garage´ didn´t do a bad job after all then. Just didn´t set the idle correctly.

[fused]

42 mpg on a 8v digi? I never knew this was possible!  on the other hand could the fueling be too lean? is there good pull through the gears? any over heating? pinking? if so need to get that sorted, if not then very nice! 

[cняis]

yes its pinking slightly, which is why it went to the garage in the first place. but it was pinking even before i adjusted the idle (i.e. at 34 mpg average). 2 garages have looked at it so far and havent come up with an answer!! 

it doesnt over heat or anything, and only pinks when under heavy load (i.e. full throttle)

the last garage that looked at it couldnt even find any timing marks on the gearbox (even took the cap off), so "set the timing by ear"  but they didnt charge me just in case it was wrong!

im half tempted to take it to a tuning specialist who might know their stuff. fed up is an understatement!

[DarnPB]

I would get it done properly if I were you. Pinking is bad news and puts a hell of a strain on the engine. Pinking is spontanious combustion and not a steady burning of the fuel. It´s caused by peak cylinder pressure being reached too soon. This is usually caused by badly adjusted timing or too lean a mixture. Or the wrong grade of fuel being used. (should be 98, not 95.)Either way, the burn heat in the cylinders is excessive, although this is not reflected by the engine temp.
Bosche agents, I have found usually know what they are doing, even on a digifant system. The didgifant system is basically an electronic version of the Bosche k-jetronic, with a few other differences.

[rubjonny]

if they set it up by ear thats why its pinking, it has to be set to exactly 6 degrees BTDC @ 2.25k rpm with the blue sender disconnected, as per my FAQ.  Did the garage know they have to remove the large round bung screwed into the top of the gearbox housing?  It's possible the top end is 180 degrees off from the bottom end too, which would explain the lack of timing marks...

[cняis]

if they set it up by ear thats why its pinking, it has to be set to exactly 6 degrees BTDC @ 2.25k rpm with the blue sender disconnected, as per my FAQ.  Did the garage know they have to remove the large round bung screwed into the top of the gearbox housing?  It's possible the top end is 180 degrees off from the bottom end too, which would explain the lack of timing marks...

They removed the bung but could find no marks, so sounds like its all 180 degrees out... what do i do?? 

oh and i always use 98 Ron