low lumpy idle

[domisgar]

hi guys.
Started my g up 2day n it took a few attempts, when it started up the idle was at just 500rpm and real lumpy. Check the battery and its was 13.75. Checked leads coil and plugs all sparking but the plugs had a load of black soot on them. Whats that mean and what could causing such bad idle?
Thanks for your help.

[G-spot]

Sooty plugs points to a rich mixture, check your CO pot on the top boost pipe, it should be reading about 550/600ohms across pins 1 & 3, if it's not, pop the plastic cap out of the end and adjust cordingly with a screw driver. 

[domisgar]

yeah checked the co pot and hue reading 550. Could it have packed up and giving duff results? Could it b 2 do with the fuel regulator? How can i test it?

[vwmk3jon]

i adjusted the Co2 pot and then adjusted the screw on the back of throttlebody and it seemed to cure the problem.

[domisgar]

checked and reset the co pot 2 600. Tried adjust the screw 2 suit. Kinda work but now it idle nice for bout 30 seconds then stalls. I fitted a air/fuel gauge. Shows its running lean? But still black soot on the plugs? Im getting so confused what going on in the engine?

[hayesey]

sounds like a duff lambda probe, when the engine is up to temp you should see it cycle between lean and rich on the AFRM at idle.  The ECU isn't using the lambda at this point, it only gets used on part throttle but if it's not working at idle then it's not going to be working at other times either.

[domisgar]

Agh right thats next on the list to change! Would a small hole in the manifold make it worse?

[domisgar]

new blue temp and lamba. still the same problem? what fuel pressure should it b running at??

[hayesey]

it's a 3 bar pressure reg but the actual pressure you see will vary depending on vacuum or boost.  But it should be around the 3 bar mark at idle, prob a touch less.  I doubt that's going to be your problem because it would cause a LOT more than a dodgy idle.

[domisgar]

just that ive noticed there no vacume line going to the regulator or the throttle body. i kno it will effect it when on boost just wondering if it makes a differents idling? and where should they be going to?