I'm building a 1986 SR5 that was "hacked" from EFI to carb. We have rebuilt a strong motor for it and installed a Weber, but I need to set the idle and high idle.

I don't have a tool with an inductive lead to read it from a spark plug wire, but did borrow an old school Actron from a neighbor that can read RPMs and such off an old school coil setup. (It doesn't seem to work off of this coil though.)

I've searched with Google and it seems there should be a diagnostic wire near the fuse block under the hood that is there to get this reading, but I can't find it. I searched the FSM and didn't see it either. The wiring harness was butchered when the PO did the EFI to carb swap and I fear it is in that mangled mess.

Can someone verify where that wire should be, color, and if it fed to the main harness going through the firewall?

Any other ideas on reading the RPMs?

 

If your truck was a SR5 then it should have had full instrumentation. The tach signal wire in the harness for the 22-re was black. It connected to the igniter through a 2 wire female plug that was green. The other wire in this plug was a black / red or might look like a black /orange that comes directly from IG2 of the ignition switch. On the igniter side (male plug) the two wires are white and pink (or red). The white wire is the tach signal wire.

 

The truck had a factory SR5 sticker on the tailgate, a factory sunroof, and bucket seats so I've assumed it was a SR5. The dash does not have a tach though. The front bumper is gray and the grill is painted black. Who knows????

I'm beginning to think the dash may have been "exchanged", but I don't know about the bumper and grill.

I'll look around for these wire this weekend and hopefully I can get a RPM reading from them.

Thanks!!!!