'88 3vze: warm idle, does ECU constantly fuel/air adjust (O2 sensor oscillate?)

[kbn]

Hi,
1988 3vze. I've done some of the typical things already, working on warm idle. Will jump to the question. I'm trying to debug a warm idle that won't go below 1250 rpm (it's a good idle though).

The FSM talks about testing the O2 sensor looking for expected oscillation at 2500 rpm. I'm fine there.

It doesn't give any info about what I should expect to see at cold idle or warm idle.

I'm guessing that seeing a steady rich condition during cold idle is fine.

But during warm idle, I'm still seeing a steady rich. (O2 sensor is new/good)

Good O2 sensor response time and swing during 2500 rpm testing.

I've gotten to suspecting my fuel pressure regulator. I get a good vacuum at the regulator during the warm idle. So the computer is trying to lean out the fuel pressure? I'm getting pulsing in the fuel return line, which I think is just from normal regulation. If I remove the vacuum line and plug it, the pulsing is the same though.

What I don't see, is the rpm increase when I remove the vacuum line and plug it. That makes me think the regulator isn't decreasing fuel pressure when it sees a vacuum...i.e. the pressure is the same whether or not there's a vacuum.

I'm going to try a new regulator, but it's gotten me wondering about what the computer should be doing during warm idle.

Do people see the Vf at the diagnostic connector swinging during warm idle, or the O2 sensor voltage at the ECU swinging during warm idle?

Another question: if you have idle at 850 rpm and you remove the regulator vacuum and plug it, does your idle go up? if so, by how much? I'm wondering about the indirect meaurement of the effect of the fuel pressure reduction.

thanks!
-kbn

[wonger]

so the issue is it wont drop its idle after warm? when warmed up. it idles at 1200rpm? i would start with checking your TPS. also where does it idle when its cold? you might just need to adjust the idle screw in