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Re: URQ sorting out
>Tonight I disconnected and grounded the temp sensor - no change in duty
>Disconnected the O2 sensor -- no change in duty cycle.
>Checked the 2 throttle switches for wiring and operation - OK, no change in
>Frequency valve buzzing, but duty cycle _won't_ change.
>My confidence is waning.
You can't give in yet, you have the engine running!. If you haven't already
checked, I would look at continuity in the wiring harness for all the
you have been checking. Unplug the ECU and work through the signals
which are going to it. If you don't have ur-q wiring diagram, Steve E or
myself can help out.
Also I remember a test which RDH posted years ago, with the engine
runnning at idling, manually activate the full throttle switch, the DC
go to 50%.
Part of old post included here
P.S. 'nuther random thought -- on my car, there is a two-conductor
"test socket" (rectangular, female connectors) dangling near
the coil. This is in parallel with the Freq Valve signal, and
should yield a duty cycle of 50%(*) when working properly. When
starting, it can go as high as 95%. So if you see any signal
present there, you know the engine computer is "working", more
or less properly. If you see no signal there, either the com-
puter has no voltage, or has "shut down" to due faulty sensors,
excessive cosmic rays, etc. This is an easy-to-access test,
as opposed to pulling the computer to get at the master wiring
harness to start checking voltages/resistances/etc. presented
to the computer connector.
P.P.S. Check the simple and obvious first. For all their inability
to use wire and connectors and relays and fuses in a safe and
sane manner, I have never heard of an engine computer failing
(I'm sure they do, but with nowhere near the frequency of just
about everything else in the car), so you can probably assume
the basic computer is behaving the way it is supposed to be-
have ("is not broken"), and thus the problem's a "simple" one
of bad wire/connector/sensor/etc. You just hafta find the sim-
ple and obvious problem . . .
(*) OK, before I get flamed -- 50% is "ideal" reading; actual will
vary depending on what the computer thinks about the exhaust
composition, in static conditions it will typically vary in
a 5% window; full-throttle should "lock" at 70-80% range. On
my car, at idle, if you actuate the WOT switch the duty cycle
should lock at 50% solid (this is a quickie self-test of the
idle and WOT switches (and computer) working properly).