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Re: Some Data Points on my sick ur-Q
I have a few data points from messing around with the ur-Q this weekend.
First off, I think I may be dealing with multiple problems, one of which
may be fuel tank contamination. I put in $10 worth of premium, and it
seems to have improved a bit.
Also, it mostly only backfires when accelerating while it's not fully
warmed up. When fully warmed up, it's hard to get it to backfire. But
it does not have the power it should in the lower RPM range.
Cam slipped a tooth? It shouldn't backfire at all. Ever. Is it running
terminally rich? What is voltage on O2 sensor?
I tried to run the dwell meter-based ECU diagnostics as shown on Scott's
page, but I'm not getting any change of the meter's default reading. The
meter is working fine, I verified it on the Coupe GT's duty cycle port.
O2 sensor bad ==> locked in open-loop. (Alternate problem: block temp
sensor bad ==> also locked in open-loop. Distinguish by watch duty cycle
from cold start -- if it starts at somewhere over 55% [high as 65%],
progressing fairly linearly to 50%, sudden drop to 39%, then jumps
back and holds at 50%, your block temp sensor is working and it's not
getting an O2 voltage it understands. If it just holds steady from
cold start, bad block temp reading. Secondary test -- hitting the WOT
switch in idle should cause duty cycle to lock at 50% irrespective of
either above scenario. I think.)
I can't find my remote starter switch, so I can't get it positioned to
what I can be certain is 0degTDC. However, someone has marked the fly-
wheel with an orange mark, the engine usually stops with that mark
lined up in the timing window, and that mark lines up in the window when
I hook up a timing light.
How can it "usually stop" like that? Unless 4 of five cylinders not
Again, since I can't find my remote starter switch, I can't do a compression
test yet. But I hooked up an outboard vacuum guage, and here are my manifold
idle: 8 to 8.5 in. HG
3000 RPM: 13.5 in. HG
Full Decel from 3000 rpm: 16 in. HG
As I recall from mine: idle is 10-12; 3000RPM is 8-12 depending (70-75mph
steady-state), unless you mean stopped in neutral, then it's 20; full
decel is 22-24. Your readings sound awfully low to me.
These figures look kinda low. I didn't see any wierd needle movements while
accelerating; I used to have a chart that correlated vacuum guage needle
ballistics to various engine problems.
Oh, the 4000 RPM cutout problem is there, for sure.
Well known, expected, fairly easy fix.
It has a noisy clacking/banging sound, not very loud, louder when colder,
almost disappears when engine fully warmed up. Hopefully, this is solid
I seem to remember checking the plugs last fall, all look fine and were
gapped properly. Worth a recheck, though...
Can't think of anything else... I did poke around looking and listening
for vacuum leaks, but no go... I had changed the smog valve with the one
on the Coupe, as the one on the ur-Q had melted a bit due to a too-close
proximity to the lower part of the wastegate... changed them back, no
difference (same part, didn't think there'd be a difference).
So, than the compression test, and other than finding a way to do the
ECU tests, what's next?
Next thing I'd do is just shoot myself (it's a lot easier and less
painful). But assuming family and friends find that unacceptable
. . . I'd check the O2 sensor voltage (easy), and the cam timing
(verify cam and flywheel agree on TDC...), since if that's slipped a
tooth or two all else will be for naught.
Oh yeah, don't forget to fix the 17 bad grounds and corroded crimp
Oh, and where the hell do you guys hook up stuff like timing lights
to get +12v when you're under the hood of an '82-83 ur-Q? Can't find
anywhere to hook up, so I used the jumper cables!