2.3L ('83-'97) Idle speed for a 94 2.3 (average)

[racsan]

So after many failed attempts for a dash mounted tach I got a tach kit meant for a diesel, it has a sensor that mounts to the alternator as its signal. Since it has to be calibrated Im not sure on where the idle rpm would be. One idea is to pull the driveshaft & have it idling in 4rth gear (its a manual) , use a mechanial tach up against the transmission yoke & see where it is, possibly turning the idle speed up to 1,000 for the calibration. The instructions say to check it at cruising speed but I have no idea what the rpms would be @ 55 or 60 mph with 4.10’s. from what Ive seen rpm could be anywhere from 600-800 at idle when warmed up. seems like quite a variance.

 

[RonD]

4cyl engines only fire every 180deg so tend to vibrate under 750RPM, where a V6 or V8 will still be smooth at 600rpm

If you have a manual shoot for 750, automatic 850

As for calibration just use pulley size
Measure crank pulley diameter, and the alternator pulley diameter

Then go here: http://gadi.agric.za/software/renting/pulley_calc.php

Pulley A is the alternator, smaller pulley, B is the crank pulley, larger pulley

Usually its "about" a 3 to one ratio, so alternator pulley 2" and crank pulley 6"
In calculator enter 2 and 6 and then, say 800rpm, for crank pulley, so alternator pulley would be at 2400rpm when engine is at 800rpm

Or use it in reverse, enter alternators RPM from tach and that will tell you crank RPMs at that time
Say alternator pulley is 2.5" and crank is 7"
alternators RPM is 2200 at idle, that would mean crank is at 785rpm

Not sure what you use to calibrate your new tach, whats the model number?

 

[racsan]

I’ll look in the morning, its in the garage. I know its a auto-meter brand, but not sure what model # it is.

 

[RonD]

I looked up autometer alternator tach....................you NEED an accurate tach to set it up................at least the one I looked at

It basically says run engine at 1,000rpms exactly and then press the button to calibrate alternators rpms to 1,000
So you will need to borrow an inductive tach(hooks up on spark plug wire), for 4cyl engine, to set up this tach

 

[racsan]

Ive got a mechanical tach thats used against the end of a shaft (like for tractor pto or for a combine cylinder speed) . I could use that at the transmission with the driveshaft off & turn the throttle stop up on the throttle body until I get to 1,000 rpm with transmission in 4rth gear.

 

[RonD]

Yes, then that would work in 4th gear on trans drive shaft output

But inductive Tachs are not expensive and easy to hook up on any spark engine, just make sure it has cylinder number selection, 1 to 8
On a waste spark system(1989-1997 2.3l) it would display double RPMs, so display of 2,000rpms would be 1,000 actual RPMs
Thats because waste spark sends a spark to each cylinder every RPM instead of every other RPM like most spark systems
If it has a Coil Pack, its waste spark