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Can I install a tachometer?

Can I install a tachometer on my pickup (87 Toyota, gas, 4-cylinder, carbureted, manual)? It isn’t made for one. How would I hook it up?

Of course you can, you would look for a gauge that screw mounts to the bottom of the dash, it will come with directions, but why do you want one?

Barky, you beat me to it.

Sure, you just need something like this;

There are lots more versions available from a number of companies and in larger sizes an they all come with instructions on how to wire them up. The Old School way to mount them is with a large worm drive hose clamped to the steering column positioned so you can see most of the car’s actual gauges.

It used to be in the conventional points-ignition days of yore any tach pretty much would work, just hook it up to the - coil lead; but with electronic ignition, which I presume your pickup has, it’s a little more complicated. There’s often some circuit loading restrictions. Just make sure the tach you buy is compatible with the ignition system you have is all.

I failed the emissions test Monday, not because my emissions were high (they’re as low as they have been for 30 years) but because the idle speed was too high.

I hadn’t driven in 10 months, so I assumed something was stuck. I took off the air cleaner and sprayed a bottle of carburetor cleaner over everything I could reach; the mechanism went from stuck to free. The engine now runs okay (the open throttle made starting hard, but that doesn’t surprise me after 10 months.) but the idle still sounds high, and the idle screw doesn’t make noticeable difference until I screw it almost all the way in.

I don’t want to fail the re-test, and I have to take it before February 6.

I used to have a dwell tachometer, the kind that required putting it into the circuit of plug #1, but that disappeared when my truck was stolen a few years ago. It was primitive and cost $15.

The only thing at Autozone that seemed to do the same was a timing light that cost $45. I don’t want to pay that much. But they had cheaper dashboard tachs. Are they accurate enough? 1200 is too high; mine was running 1300. Toyota spec is 700.

Maybe they will lend me a timing light.

Should I be able to turn the idle down so low the car won’t run? I can turn the idle screw to the point that it wobbles and I worry it’ll fall out, but it keeps on running.

The old GM HEI distributor caps made tach installation easy. It was marked for the tach lead.

So what will the tach tell you that you don’t already know? It wil tell you the trucks going to fail emissions again. Don’t waste your time and money on adding a tach.

Fix the problem with the carb! If you adjust the idle screw until its loose and the idle is still too high then air is getting past the throttle plate. The carb needs a rebuild because there is trash inside or a gasket has failed or a diaphragm is blown. Ignore the tach and get to work!


If the idle is < 1200 I can pass the emissions test now, take my time rebuilding the carb (original, never re-built), a big job I have never done.

Not a big job, just a fiddle-ey one with lots of small parts. Rebuild kits come with instructions, take your time and give it a try.

If you have access to a lab o’scope, for a one time deal, just wrap some magnet wire around the number 1 spark plug wire a dozen times or so, then connect the ends of the magnet wire to the scope probe. You’ll get enough inductive pick up to see the number 1 ignition pulse on the o’scope display and can time it pulse to pulse on the o’scope to figure out the rpm with some simple arithmetic. I did it that way on my Corolla prior to most recent emissions testing.

Please see next post by @RandomTroll What's this other adjustment screw on my carburetor? he she it found the idle adjustment screw on the carb.

Your underhood sticker lists a specified idle speed. When it comes to the typical smog inspection, you’re only allowed a few rpms variance. If it’s too high or too low, by a wide margin, you fail. If the sticker says 700rpm, and your truck is idling at 1100rpm, you’ll fail the test, no matter how clean the tailpipe emissions are

Why are you fixated on getting the idle below 1200rpm. Your goal should be a well running engine at 700rpm

Your '87 Toyota pickup uses a distributor based ignition system, and installing a tach should be easy. For diagnostic purposes, which if I understand you is what you want a tach for, a simple dwell/tachometer with an inductive pickup is all you need. Instructions for use will come with the device. It’s been many years since I bought one, but I’m sure they’re still available at parts stores. There’re still a lot of old vehicle afficiados around.

However, IMHO trying to adjust the idle without correcting the cause of the problem is futile. If I understand your posts correctly, this carb needs to be rebuilt. In short, I wholeheartedly agree with Mustangman.

I need to pass an emissions test soon, perhaps sooner than I can fix the problem. Seeing as how I don’t drive it but a few times a year (haven’t since April, until I needed to get this test.)

It passed the emissions test, with numbers as low as ever. Once I got the throttle unstuck it sounds okay.

I watched the display during the test; only when it exceeded 1200 did it object.

I want it to idle at 700. I want to fix it at my leisure. I have other things to do. It will be easier and cheaper if it’s licensed, even if the idle is a little too high. I promise not to drive it until I get the idle down: will that make all you scolds happy? I don’t need to be told these things. I asked for help, not lectures.

Mark Twain had to rely on locals to advertise his appearances (he had no advance man). When he got to town, if somebody had advertised his presentation as a lecture, he remonstrated with him, ’ I don’t lecture: lectures annoy people.’

I already found the ‘idle speed adjusting screw’ 20 years ago (according to the pictures in the Chilton’s and Haynes.) I found a different screw, one that sets the minimum position of the throttle. The throttle rests against it (or would, if it were screwed in enough). Could it be the ‘fast idle adjusting screw’ that other Toyota engines of the same era have?

What does the ‘throttle positioner adjusting screw’ do?

I’ve passed with the idle as high as 1169. Getting it running well at 700 is my goal. It’ll be more convenient and cheaper if it’s registered.

Then you live in a state with EXTREMELY relaxed standards for smog inspections

In California, you would fail, no ifs ands or buts

That may vary from state to state. In WA the idle speed simply needs to be between 450 and 1100 rpm. If the idle speed is too high the car won’t fail a test, it just won’t be tested–no harm, no foul.