I have a '96 2wd 4runner. I bought it used for the wifey to chase groceries in.
It's really clean, and she likes it.

So far, it seems like it only has one problem.

The tachometer acts wierd. I believe that it reads too high.

At idle, it reads 1k. At 70 mph, it reads about 3k. if I push the pedal down enough to make it downshift, the tach will swing around to where 9k would be before it shifts back up. I'm talking about having the tip of the needle down where the idiot lights are!

I don't think that the motor is over-reving. It doesn't sound like it's turning too fast. I havn't heard any rev limiter stuttering. Besides, I'm pretty sure that 9k would have that motor flying apart. I believe that the motor is doing exactly what it's supposed to do, but the tach is reading wrong.

My first thought is that it has a 4cyl tach installed in the dash, and the 6cyl firing order is making it read high.

I can't see any sign that the dash has been apart, so if somebody was in there it was at least somebody that could pull the dash without tearing things up.

Have any of you seen this before?

Does anybody have any suggestions?

Does anybody know if the tach drives off of the ignition, or does it get a signal from the computer?

Any help would be apreciated!

Fast Frank

 

sounds like someone took it apart, removed the needle and put it back on in the wrong place

 

Is that possible?

In order to go all the way down by the idiot lights, it's about 1/3 of the face from where it should be.

It seems like doing that would have it reading 4k at idle.

If the needle was mounted that far from the correct position, would it go to zero with the motor off?

Fast Frank

 

on most tacks when the engine is off, the needles goes down way past 0 rpm

 

There's a peg at zero, the needle sits on it when the motor is off.

Fast Frank

 

I think that there is something else wrong with it something messed up electronic like. also if it was a 4cly tach i think it would read slow

 

Four cyls fire two times per revolution, six cyls fire three times per revolution.

More sparks per revolution= higher reading on the tach for the six cyl.

That's IF the tach is reading the ignition. If it's getting a signal from the computer, all bets are off.

Fast Frank

 

ah silly me

 

I'm hoping that somebody is going to tell me how to recalibrate it, or something.

I don't think that anything is wrong with it. it seems to read fine, just high.

Back in the "Good old days", a tachometer had a switch on the back that would let you calibrate it for 4,6, or 8 cyls. I'm doubting that I will find one of those on my 'Yota. Maybe a jumper that I can move?

Who is the electrical guru around here?

Fast Frank

 

Acording to the diagram, it is fed from the ignitor. I dont see any selector switch, but it doesn't mean there isn't one.

 

that could be a good explaination. if it was a 4cyl tach then it would probably read about 3/2 too high on a 6cyl. so if the idle was 750 (which is what i expect) the tach would read 1125 at idle. and if it's shifting at 6000, then it would read 9000, like you say.

you mentioned that older tachs had a switch to pick the number of cylinders, what that switch does is select which resistor to use in the counting circuit. it's been a while since i've played with that stuff, but i think you'd need a resistor thats 1.5 times bigger than what's currently in there. so if you can measure what resistor you already have in there, and then add another one in there that's 50% of that size, it may solve your problem. or you could just solder a potentiometer in there and then you can adjust it to read what you need it to.

 

in a cluster the best way imo would be to replace the tach machenics to a 6 cyl models....you can probably dissemble it and find the proper resister if you know your stuff...if thats even the problem to begin with...

 

Thanks, Yoda.

Now that I know that it's reading the ignition instead of some digital mumbo-jumbo from the computer, I'm thinking that maybe I can do something with it.

I'm having a hard time believing that Toyota would specify one tachometer for the six cyl stuff, and another tach for the fours.

I bet that there's a way to make it do both. now, to figure out how!

Fast Frank