lean fuel trims?!?!?

Hey

my car has always been known to me and whoever has seen it for being stupidingly rich.
the fuel trims from time to time where down to like 78% or so.

I have done a few things including upgrading the fuel return system to lower the pressure to get it right.

Recently I got the lower honey comb out and not the fuel trims are at 130% to 140%

would that cause such a drop in air metering accuracy?! is the car so lean now?!

I know the intake leaks and that should if anything make it rich?!


what is up?

An intake leak will make you rich at WOT (ie:under boost) and can make you lean at cruise (ie: under vacuum).

I've been trying to figure out my trims also. I have the lower HC out, screw backed out, pump rewire and my trims are maxed.

It's weird. When my O2 volts cycles super quick up/down my O2trim is between 80-110 which is where I would expect. However, when my O2 volts cycles slowly (more of a sine wave) my O2trim jumps to 140ish!

I also get random 43 count knock when everything is looking good and I'm just cruising.
My O2 readings are between 0.14 and 0.90 and at WOT I'm 0.9volts.

I've even had the occasional 93% injector duty cycle show up for a split second. Makes no sense.
It's like the things on drugs, none of it jives.

What Steve said makes sense. Guess I have to look for an intake leak now.

t.

Steve,

I guess that is true if the leak is after the throttle,
otherwise I would thing there is actually positive pressure right up to the throttle.

There is small leak through the shaft and a very small one through the BISS. But would that cause the thing to be 140%!

the plugs where a bit white but the logger never shows any knock. (getting off the throttle it does like 4-5 counts)

All I know is: if I have an intake leak anywhere between the turbo outlet and the intake manifold, my low trim goes up, and my high trim goes down.

Take what you will from that. I'm not going to try and draw any concrete conclusions, or make any theories from it. All I know is that's what I see.

<shrug>

put the honeycomb back in and the fuel trim droped to 80%. that is about 80% drop from what it was (160%).

how restrictive is this little crap!!!!

back the screw out till you hit 100% with the honey comb in.

All mafs are different. Some seem to be affected dramaticly by the removal of the honeycomb or any alteration from stock form.