I have a '94 Legend L, with about 110k miles. Actually it is my wife's ride. As I we were on a trip last weekend, I noticed the speedometer was not correct, and by using a stopwatch and mile markers, I discovered the speedometer was reading faster than I was actually going. When the speedometer reads 70, the actual speed is about 65 or 66. Is this likely a bad VSS?
-Jim

 

no the vss is working fine.

your talking about 5-7% inaccurate

are you running correct tires?

ever have the transmission overhauled?

was it a metric stop watch? (just kidding)

 

I will verify the tire size is what is supposed to be on it. Is there any adjustment that can be done to correct the speedometer?


"was it a metric stop watch?". . . thanks for the laugh.

 

I forgot to also answer the other question. Trans has not been overhauled, but has been flushed at least twice in the past 10 years. Other than replacing the Timing belt and front rotors, we've had no problems.

 

at this time im not aware of any adjustments on the speedo system.

it may be such a thing that a dealer can reprogram the ecm for your
current tire size. btw if its been off for the entire 100k+ miles
then your

odomiter is fast by 5-7% as well.

 

With regard to tire size, the book calls for 205/60/15. Tire size currently on the car are 215/60/15, which isthe size for the GS model. Not sure about the electronic Speedometers, but for cable driven Speedometers, a larger tire size would make the Speedometer slow, not fast. I called the Acura Dealer here in Wichita late yesterday to see if there was something they could adjust. They were of no help.Guess I may just have to live with it.
I will keep checking back in hopes someone will have an idea.


Thanks for your help/ideas
-Jim

 

Jim,


The speedometer is electronic and driven by the PCM (ECU if you have a manual transmission). No drive cables involved; a sensor monitors output shaft speed. The PCM computes speed by counting pulses or measureing pulse width, then doing a bit of math, and finally driving the speedometer with a DC voltage and pulse for the odometer solenoid. The GS has a different PCM from the L or LS models with different computation constantsto compensate for the different tire size.


I run 205-65-15 on my 95 L. The only checks I have been able to use are the Radar devices placed on the highways to scare motorist into slowing down. Those usually indicate a slight 1 or 2 mph below what my speedo reads. Before switching to the larger size tire the error was about twice that.


You should expect your actual speed to be greater than the speedometer indicated by the percentage of difference from standard tire circumferance and the oversized tire circumferance. Unless the check range is calibrated, inother words the road department placed the mile markers in the correct locations, you can't trust the distances to be exact; they could be off 5 or more percentage points. Your thumb on the stop watch button may be off.


Your results indicate an error in the opposite direction, such as you have smaller than normal tires mounted. Recheck you computations ortry using a table generated in a spreadsheet.

 

the tire isnt considered an over sized tire because the hight of the tire didnt change. the only differencein the tires are that they are about a half inch wider and that wont affect your speedo. now if they have a lower series tire or larger series tire then you would need to to get the correct tires put on or have some adjust your speedo.

 

going from a 205 to a 215 would affect speed by less than 2%



and tire width would affect your over all tire size because your side profile is a % of your tire width



a 335/35/17 is 26 inches tall and so is a 265/45/17



35% of 335=11.7cm of side wall that = a 25.83 total tire size

45% of 265= 11.9cm of side wall that = 25.98 total tire size



eithor way i dont believe your tires are off enough to cause your speedo issues.



imo it time to hit a dealer and see if thay can calibrate it.

(by reprograming that comp)

 

btw there are pulse modifiers out there that take a input pulse and
read it and send out a pulse that is different according to a preset %
difference requested.



look up speedo shops in the phonebook/ online.



and putting 1 on your rental/leased car will get you arrested. if done for the wrong reasons.