Analog Tach Help

[oldgeek]

The 2.3l truck doesn't have a tach. I have two things available to try to figure out engine speed. One is a multi meter that has a Hz reading. The other is this old analog tach. I stick wires into one side of a coil pack. I get a reading of a bit under 3000rpm on the 8 cylinder scale. Using the multi meter I get a reading of around 9.3Hz which multiply by 60 comes to 558 cycles a minute.

Now with the tach, I'm thinking that one side of the coil pack would fire every revolution. A single coil on an 8 cylinder would fire 4 times a revolution, right? So I would assume that the scale on the tach would read the same for a 4 cylinder with coil packs. But it doesn't feel like it's idling at a bit under 3000rpm.

I'm confused.

 

[oldgeek]

Never mind the multi meter. I'm getting different results from nearly each spark plug wire

 

[2011Supercab]

A single coil on an 8 cylinder would fire 4 times a revolution, right?

Unless it's a waste spark system

 

[oldgeek]

This analog meter is old. The leads connect to the wires powering the coil.

 

[scotts90ranger]

The tach signal on those is odd, it's waste spark and does fire every revolution.

The great question is why are you wanting to know the engine speed? For curiosity sake setting the idle screw or something? Or are you looking to put in a tach? If you are wanting to add a tach your best/easiest option is a stock tach cluster, it's a simple swap and you can keep your original speedo/odo easily, you just need a cluster from a mid '92 model year Ranger or Explorer (as long as the explorer has a 6k tach, it's been 12 years since I've had one...) through '94, they looked the same from '89-94 but mid '92 was the split for the wiring change. Doesn't matter if the cluster is from a 4 or 6 cylinder, it figures that out somehow...

 

[oldgeek]

The tach signal on those is odd, it's waste spark and does fire every revolution.

The great question is why are you wanting to know the engine speed? For curiosity sake setting the idle screw or something? Or are you looking to put in a tach? If you are wanting to add a tach your best/easiest option is a stock tach cluster, it's a simple swap and you can keep your original speedo/odo easily, you just need a cluster from a mid '92 model year Ranger or Explorer (as long as the explorer has a 6k tach, it's been 12 years since I've had one...) through '94, they looked the same from '89-94 but mid '92 was the split for the wiring change. Doesn't matter if the cluster is from a 4 or 6 cylinder, it figures that out somehow...

One of the codes throwing out is:
411 (R) Idle speed system not controlling idle properly (generally idle too high) – ISC

I've taken off the IAC. The valve does not shut all the way, even if plugged in and key turned to ON (which the plug has 12v when ON). I don't know if that's normal. I'd just like to see what the idle rpm's are for reference. I don't want to spend the funds on a new IAC if it's not necessary.