1988 Chevy Sprint

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billscorpio - 29 Sep 2006 23:06 GMT

I Have this Sprint and I can't get it to lean out the mixer control
selenoid unless I ground the blue wire with red stripe which the
computer is supposed to ground. At first the selenoid wasn't working so
I installed another one that does work. I watch a volt meter connected
to the o2 sensor to see if the computer is trying to control the ground
and it doesn't. Do I need a speed sensor signal for the feedback to
work?
I do have some high ground resistance in a black wire with a green
stripe, .99 MV, does anyone know if this is a computer ground? It runs
lean at idle .230 MV, and real rich at 3000 rpm 1 volt and higher,no O2
switching at all. Has anybody ran into this no feedback problem? Any
and all help and any idea somebody might have has to why the feedback
system is not working right will be greatly appreciated.

Thanks, Bill

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Mike Romain - 30 Sep 2006 01:04 GMT

On an 88 I would make sure the body has a really good ground path to the
battery. When the ground connections get corroded or go rotten like
some mesh straps do, the computer can loose it's ground tag and things
like you describe can happen.

I live in the rust belt and see it all the time on various vehicles.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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> I Have this Sprint and I can't get it to lean out the mixer control
> selenoid unless I ground the blue wire with red stripe which the
[quoted text clipped - 11 lines]
>
> Thanks, Bill

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jdl - 01 Oct 2006 22:18 GMT

Was the vehicle running poorly, any codes? How old is the 02 sensor?

I've seen brand new, one wire 02 sensors, that would not switch at idle,
not getting hot enough. I would go off idle, a few rpms, and the thing
would start switching like crazy.
If it won't switch at lower rpms, try to richen the system, see if the 02
sensor voltage changes.

At higher rpms, some systems will go into open loop. The computer won't
pay any attention to the 02 sensor.

The last feedback carb I worked on, I hooked a dwell meter to the M/C
solenoid connector, to see what was going on.

I can't tell by your post, what tests you've tried.

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billscorpio - 03 Oct 2006 16:01 GMT

Thanks for your replies, Have a great day!! I am getting no trouble
codes. The car runs fine, it just has a high HC & CO reading when I
take it to get smogged here in CA. I will try a dwell meter in the MC
circuit. The O2 is a new one, it responds to both lean and rich
commands, low&high MV readings. When I tap into the MC selenoid wire I
get battery voltage which gets no ground to the computer, I go back to
the computer and at that point I still read battery voltage, so the
wire has continuity. Though I haven't checked yet to see if possibly
another return voltage wire has shorted out and burned into the MC
selenoid wire. Now I can ground the Blue WRed stripe MC wire and the O2
will lean out. The wiring diagram I have for this is not a very good
one to follow, it is a do it yourself chilton1985-93. Thanks Again,
Bill

> Was the vehicle running poorly, any codes? How old is the 02 sensor?
>
[quoted text clipped - 11 lines]
>
> I can't tell by your post, what tests you've tried.

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