Help! A/F Lean!!

[LevinGT]

Okay i have this problem; when engine is cold mixture is rich, which makes sense, while driving A/F goes up and down. Still makes sense.
But then, as engine warms up, after say 20 min. at WOT A/F goes lean @ 3000 rpm till redline?
But only while driving, then as you stop and idle still lean, after 1 or 2 min idle A/F goes stoich. When revving A/F goes from rich to stoich, and everything seems normal then.
It's just a simple A/F meter, so I don't know how lean it's getting.
Any ideas?

[Aico]

No way to tell with a narrow-band.

[jamiemirror]

Change the rubber line to the MAP sensor.

[LevinGT]

thanx jamiemirror,
today i replaced all the old, dry vacuum lines. seems like it did help a bit, the new lines fit much better, the old one came off way to easy.

[jamiemirror]

You are welcome, LevinGT !
I prefer to change these lines instead of check - this is cheaper.
Often the MAP line is broken but you can't see that (the problem is on the back side ot line near the MAP sensor - must touch that place with fingers and feel notches from broken rubber). Another problem with "lean symptoms" are failed intake gaskets (don't forget - 2 gaskets because of TVIS plate).

[LevinGT]

the intake has never been removed, so gasket should be allright. should it? noticed one more thing yesterday, after pushing engine a bit harder, idle up 150/200 rpm, now idle @ 1000 rpm. strange?

[jamiemirror]

LevinGT, you can check intake for gasket leak simply by spraying some water (when the engine idles) on these gaskets. If the RPM start to vary - change the gaskets (~9EU from the dealer).