[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

1983 UrQ duty cycle

With the turbo problems I decided to finally check the mixture
adjustment. I warmed the car up, plugged the breather hose
and the inlet for the carbon canister and checked the idle
speed, a little high. I could easily adjust it up and down. Does
that mean I don't have a vacuum leak, 'cause lord knows I have
replaced just about every vacuum hose on the car. Then the
duty cycle check. It was high, fluctuating with an average of
75%. That's out of spec. I tripped the WOT switch and got a
steady reading in-spec with the intro service literature.
Disconnected the O2 sensor and got a steady 50%. All this
seems right. With the O2 sensor disconnected and 50% duty
cycle I adjusted the idle speed and instead of being screwed
all the way in to the stop, the screw was at the mid-point
travel. Then when I connected the O2 sensor back up the idle
speed was like 1200rpm. I'm sure this is because the duty
cycle was now back to 75%. So I adjusted it back down to a
reasonable level (880). My question is this: would this explain
why my closed loop or is it open loop (startup condition) has
such a rough idle. On startup I get a duty cycle of a steady
50% until it goes open or closed, so with this duty cycle the
rpm is way too low and therefore the timing not advanced and
hence rough idle. I have a bad cold so if none of this rambling
make sense, ignore it. I'm looking for a few pointers from some
experts out there. By the way, I don't own the 3mm CO
adjustment tool yet so that's why I didn't try to adjust the duty


Andrew Finney
1983 UrQ.