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Tach problems on 91 2.3l ranger


New Member
Feb 6, 2010
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Hey everyone. I'm new to this forum, but I have been using this site for a while now and I find it extremely helpful. I can usually find an answer to my problem, but I wasn't so lucky this time.

The tach on my 91 ranger (with the 2.3l dual plug system) hasn't worked right since i bought the thing a couple years ago. At an idle, it reads below 500 and when revved it never goes above 2000rpm. When driving normally, it hovers between 1000 and 2000. So, today I decided to try and see what was up. I started with swapping the tach altogether with a different, working ranger tach i had lying around. Problem did not change. Then I started investigating the DIS module. Everything seemed to be in order there, except something caught my eye. There is a wire going into the bottom plug on it (i think it is orange with a red tracer, but i could be mistaken) that is supposed to be the ignition ground from what I can understand. On it there is a bare wire wrapped onto it with foil tape all the way up. Now I know this bare wire is not supposed to be dangling loose, so my question is, where is it supposed to go? Does it ground onto something, or is it supposed to go into the same hole on the plug as the ignition ground? The reason I am so confused about this is that someone had replaced the bottom plug of the dis module and spliced all of the colored wires to the wires on the new plug. I don't know if this bare wire is supposed to be included in the splice along with the orange/red wire, or go elsewhere. And to further my questions, does this wire have anything to do with my tach not working right?

I did some research earlier today, and found out that the tach gets its signal from the black/yellow wire on the bottom of the dis module (the IDM wire). Is this correct? And is it in any way connected to the bare wire I'm having issues with? The truck runs perfect, so I think my dis module is still working correctly, so I'm at a loss of what do do.

Also, I forgot to mention that I did get the codes from the koeo test (18- TACH signal erratic, and 88- IDM,DPI, or Spout circuit fault).

I know my explanation above may be a bit confusing, and I can try to get pictures of that bare wire tomorrow if needed.

So anyone familiar with this setup able to help?

Thanks in advance

Oh, one last thing.... does anyone have a wiring diagram for the dis module and surrounding wires? I know its a longshot, but it would probably solve my problems.

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