Tps and more.
 

Have been having problems with the rear cylinder running lean.
Have reset the tps to 150mv butterfly fully closed, set throttle link with vac guages to achieve good ballance through rev range. Thus far all well.
Next step connect up co meter to both exhaust ports and trim air bleeds to achieve good co balance. This is where the problems start. Co on rear 3%, front 8% Finally got co balance with rear air bleed fully closed and front open about four turns. Cylinder balance is now around 3 inches hg out.

Any coments folks?

Always go for CO balance over vacuum. Did you adjust balance bar with air bleeds fully closed?

Hi Nelly.....Yep balance was done with the air bleeds closed. Its just that I cant remember it being this far out the last time I did it. Had a good look around and couldnt find anything wrong. Checked belt alignment and tension, Compression test was in balance, Changed coils and leads over, new plugs, changed injectors over all to see if it made any difference, but didnt.
Couldnt find any leaks in induction side or any leaks in the exhausts. Just seems a bit odd to me.
As you say, co balance is the most important, so it is set now, just got to take it for a road test to see if its all ok.
Just another question. Is there an offset in the rear cylinder fuel mapping on this (st4 2001)?