L-Jet going full Rich on Deceleration Options

[Brian Fuerbach]

1974 1.8 with L- jet. Been playing with a wide band air fuel meter and noticed that when I lift the throttle the AFR goes to max value on the gauge. I thought it was supposed to go lean. I checked the throttle position switch and it checks out fine. Going to check the wiring harness next.

What else should I check? Decel valve?

[emerygt350]

Is this correct?
I know they changed stuff every month on these things.

[emerygt350]

If it is, man that doesn't make much sense to me. Why would you pull air through the AFM bypassing the throttle blades? There must be an 'on off' with the TPS. If throttle is closed, don't listen to the AFM. At that point, why not just suck it before the AFM for the decel?

[Van B]

If it is, man that doesn't make much sense to me. Why would you pull air through the AFM bypassing the throttle blades? There must be an 'on off' with the TPS. If throttle is closed, don't listen to the AFM. At that point, why not just suck it before the AFM for the decel?

TPS really only knows when the throttle is open (not at idle) and when it's full throttle. Everything is driven by the AFM. It's a v1 MAF really.

If @Brian Fuerbach can confirm the opening vac for his decel valve than that will give a clue into whether the AFM is sending extra fuel even when the throttle is closed. I'm a little skeptical about that because if the decel valve was sending air, I would expect to see rev hang i.e. very slow wind down of the engine from high RPM.

My money is on the timing. too much advance at high RPM + not enough air = incomplete burn that is picked up by the AFR.

[emerygt350]

Too much advance could certainly do it, but there should be a healthy fuel cut too. If the TPS is saying the throttle is closed, the AFM should be ignored (well, idle level), and the decel pulling air from the boot and dumping it into the plenum should (should) cause a lean mix. And add to that the vacuum on the fuel regulator. If that is all working correctly then the only thing left is advance. Or just normal behavior. Not like many of us have AFRs. Wish they were more common and less expensive..

Speaking of that, Brian, out of curiosity, where is your O2 sensor located?