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?

[wonkipop]

@Emerygt350 .

always have to go back and re-read this Ljet stuff carefully.

not sure if 1,8s incorporated the fuel shut off thing.
may not have been in all L jet systems, just for some cars.
someone like clay perrine would know.

1.8s definitely had spark cut off via the rotor for over rev.
whether that cut off fuel too i don't know, but i don't think so.
reason i say that is 75 calif 1.8s had a whole separate switch to cut off fuel to stop catyliser being ruined.
but as to coasting over-run, not certain. maybe note posted above inaccurate.

def adjust fuel pressure.
at low vac situations its 35 lbs.
and at high vac it reduces to 28 ilbs.
you test that as part of standard testing.

very definitely the throttle switch takes over at WOT.
just full on gives you fuel.
less clear about what tps does at idle (or throttle closed).
thinking about it, i believe its the AFM does it all.
when the throttle is closed the switch is simply sending a signal to the ECU that its closed. and ECU then knows this and does its routines based on other inputs.
i think only time ECU overrides the AFM is WOT and gives full enrichment.

so......
just not sure what could cause richness on over-run other than Van's suggestion that the distributor does the clean up via the timing. the fuel pressure lowers to assist due to high manifold pressure. and the ECU knows that the throttle is closed, but the engine revs (spinning) are high so it does an adjustment to the enrichment the AFM would usually signal at the flap position it is at because the decal valve being open (which is happening simultaneously with the fuel pressure regulator lowering fuel pressure).