1994 Toyota Corolla Speedometer Problem

Chances are on a '94 it's still mechanical, and a couple things are going on here:

The 'clockspring' is going away (but not that likely)

The cable is biting the dust. This makes more sense, since it is affected by the brakes. Maybe the cable's binding on something.

If it's electronic, then I would look for a loose connector or a bad ground.

If it is a mechanical speedometer, then the speedometer head is probably bad.

It's mechanical.

How do I change it and where is it located?

Gee, Ray, I've never had one of these go bad!

On my '74 1200 the speedo started doing what he's describing, and "Rusty Jones" greased the cable!

I'm wondering if I sell the car do you think it will pass smog?

What I mean is do the people look at the speedometer as one of the requirements, or do they just go by there RPM's from the machine?

My speedo in my Supra is stone cold *BROKEN*!! (Well, the connector from the tranny is).

Check with someone that does inspections as to what the regs are in your area!

I'd go with Hachi on this one ....start by lubing the cable, and if it's still erratic, replace the whole speedo head.

The speedometer cable is the more likely suspect, can be disassembled easily for inspection, and is a whole lot cheaper to replace than the speedometer head. When it starts going bad it snags and when it 'unwinds' it makes the speed indication bounce up.

Take the cable loose from the transmission and the back of the speedometer head. With both ends loose, a good speedometer cable core should spin easily with finger pressure. If it jerks and fights, or sticks, it's bad.

The core pulls out in one direction or the other, there's one end with a thrust flange on the drive tang or square drive adapter, and one that's sized to fit through. If the core is tight and intact the entire length, clean it off and grease it with a white lithium grease or a motorcycle cable lubricant and put it back.

If it's sprung and frayed, replace the core and the casing as a unit

- the inside of the casing gets damaged by the sprung core, and it will damage a new core. And if it's sprung badly the core won't pull out easily (or at all), if you do get it out it will never go back in.

Treat the new cable and core gently, you can kink and ruin them by installing it roughly and bending it tighter than the allowed limits.

-->--

And, DON'T use WD-40. I would say PB Blaster, but I have found something even better than that. GM Penetrant and Lubricant. Comes in an aerosol can and runs $8~12 at your local GM parts counter. Superior stuff!

The speedometer head is located in the instrument cluster - it is driven by the speedometer drive cable from the transmission and includes the head, gauge, and needle. To change it, remove the instrument cluster, disconnect the cable, unscrew the speedo head, and reverse the process. You need to attach a label in a conspicuous place to note the correct mileage when the old one was removed.

After driving with the needle pegged for a while, the speedo head starts bouncing all over the place. This was a problem when the max indicated speed was 85 MPH ;-)

I doubt if this is the cause of the OP's problem, but the result is the same.

Whether the car will pass smog depends on the laws where you live. I doubt if a speedometer reading is necessary to pass a smog inspection but it probably will not pass a safety inspection if there is one in your state.

I could be wrong, but speedometer cables in Toyotas generally make noise before they start causing erratic readings, and the complaints I've seen generally are a needle that wobbles, not one that reads 0 and then too high. Anyhow, a cable is a less expensive fix so it wouldn't hurt to fiddle with it first.

No - "pegged for a while" on a mechanical speedometer system indicates something mechanically wrong in the speedo head, the reluctor cup is making physical contact with the spinning magnet (driven by the cable) to toss it to full scale.

Or it's got a big glob of grease or other high-friction gack in that gap that's effectively doing the same thing - dead bugs? Spider eggs?

But reading 0 (stopping) for a while and then going way high before settling down and reading right (at least for a few seconds), with the odometer dials doing the same thing, that would be a speedo cable binding and jamming (and slipping somewhere at the transmission drive gear end most likely) and then freeing up and zinging the needle high as it unwinds.

That's always a good clue - if the speedometer reads crazy (0 MPH or

9999 MPH) but the odometer is still ticking up miles like normal, the cable is turning like normal. THEN it's in the head, gaaa-ron-teed.

If they aren't listening for odd noises, they could easily miss it.

I'll hear an odd noise (sometimes rather loud) in a car or a piece of equipment and know what it means, point it out to the owner of said equipment, and they'll invariably say "Gee! I never noticed..."

Lots of mechanical and electronic things in this world will give you a whole lot of advance notice that they have problems /before/ they break - if you know how to listen to what they're saying. ;-)

You can call me "The Car Whisperer." (Among other things.) ;-P

-->--

How long's it been? Thirty-three years? OK.

Maybe it had to do with the Toyota Warranty Extension Plan. I was putting about 500 miles a week on my '74 Corolla 1200, and was chewing through the warranty pretty quickly.

Didn't take me long to discover I could reach up behind the dash and yank the cable head out of the speedo...

That was when I was young and stupid and only had one car. Now I put the high-mileage on the beaters. I bought the Scion in September w/11,995 miles, and it has about 15,500 on it now. The Supra and the Mazda take the brunt of the mileage...

Good point about the odometer acting weird while the problem is occurring!

The speed indicator has no direct connection to the driver on a mechanical speedometer. There is a magnet connected to the driver that rotates around a drum like receiver connected to the indicator. If the needle jumps it in generally caused by a cable in need of lubrication or a worn cable or housing that is causing binding.

mike

Gee, the driver just looks at it. I never had a direct connection to my speedometer when I was the driver. In fact, I would have to take apart the dash to just touch it. ;-)

Jeff

Well, you know they say the hardest part of a car to fix is the loose nut behind the wheel!! ;)