wrong speed on speedometer

[cIutchkick]

i took my car to the highway today, got on it a little to match speed of traffic, i look down and my speedo and says im doing 95mph. i kno i was not doing over 70mph. what suggestions you have? im running a bone stock 89 ka24e. my brother has a 89 coupe i can get a hold of to switch out the cluster to test it out but would prefer hearing from you guys first instead of taking apart the 2 cars. thanks in advance

[5t341tH]

did u change to bigger wheels recently?

[BoostedCoupe]

In my friends car his speedo got messed up some how. IT skipped 10 or so mph. We fixed it by. Pulling his needle off. then cranking the car then putting the needle back on. His speedo is fine now. your problem might be the speed sensor on the transmission. But you could give my method a try.

[ZX88]

damn you must be running 22 for it to be that big of a difference in running 17s and my speed is off by ~5mph

[BoostedCoupe]

I dont think bigger wheels mess our speedo's up, since our speed is caculated from the trans.

[luftrofl]

did u change to bigger wheels recently?
damn you must be running 22 for it to be that big of a difference in running 17s and my speed is off by ~5mph

Wouldn't larger wheels make the speedometer read lower than your actual speed? (Fewer rotations for same distance with a larger wheel)

I dont think bigger wheels mess our speedo's up, since our speed is caculated from the trans.
... which is connected to the wheels

[brokeAs240sx]

did u change to bigger wheels recently?

Even if he did, don't think it would cause 25mph off, haha.

There's only really 2 things that go wrong - either speed sensor or gauge itself - usually, if speed sensor is broken, then it won't really display speed @ all.

My car had the same problem (but only by ~5-6mph). Swap out the cluster & see, sohc clusters are really cheap, too.

[aznpoopy]

not bigger wheels alone

bigger overall wheel/tire diameter

and yes it does, but certainly not by that much.
and if im not mistaken a bigger combo makes you read slower

[Oo_Skyline_oO]

actually, I'm having the same problem, except I went from SOHC to DOHC

[jinesz32]

speed sensor?

[cIutchkick]

thanks for all the responses. i will try what you have posted and let you kno if i come up with a solution. wheels im running 962 staggered 17s, but they were already on the vehicle when i purchased it. but i agree i dont think 25mph would make that much of a difference. but it is weird because once the speed displays around 50 it climes faster than it did below 50.

[jinesz32]

my speend sensor is wrong, in 3rd gear i can go past 120 all the way to the pin, rofl! so i just unhooked it :D

[brokeAs240sx]

thanks for all the responses. i will try what you have posted and let you kno if i come up with a solution. wheels im running 962 staggered 17s, but they were already on the vehicle when i purchased it. but i agree i dont think 25mph would make that much of a difference. but it is weird because once the speed displays around 50 it climes faster than it did below 50.

I just looked @ mine closer tonight & I think you have the same problem I do - the speedo gauge itself on the cluster.

I compared vs the display on my power fc (km/h) & a couple "Your Speed is: XX" Radar displays in my city.

I noticed below 45-50mph, the gauge itself is only slightly off from the power fc reading (about 1-2mph). Once I hit the freeway, if I floor the car and keep load high enough to be in the 80ish mph range (slightly faster than traffic), the powerfc will be drastically different than the gauge - sometimes I can get the gauge to say I'm going 95-100mph, but the power fc reads something more accurate (direct from ECU).

Of course, even then, my speed is still off because of my differential & wheel size, but it is fairly obvious that the culprit is the speedo gauge itself - especially since I've gone through several different digital & analog gauges.

Easiest fix is to swap in another one. If you want to try fixing it, you can always install a potentiometer - not sure if the write up is still available, and make adjustments @ certain voltages, etc - specific #'s & voltages can be obtained either by trial & error, and possibly the FSM.

/end thread?

[xsparc]

I noticed below 45-50mph, the gauge itself is only slightly off from the power fc reading (about 1-2mph). Once I hit the freeway, if I floor the car and keep load high enough to be in the 80ish mph range (slightly faster than traffic), the powerfc will be drastically different than the gauge - sometimes I can get the gauge to say I'm going 95-100mph, but the power fc reads something more accurate (direct from ECU).


The speed is given to the ECU from the cluser....

But yea.. sounds like a bad cluster

[gnxregal]

I have a simular problem, HUD reads zero with switch on, but when started HUD reads 12 mph at idle. Any ideals on a fix.