speedo question

[94conv.]

Ive been searching forums but havent found anything substantial yet. My speedo was reading around 35 - 38mph and I know I was going that fast, maybe 25. Tried running with trafic but couldnt tell anything definate. I did notice its slow to return to 0 after I stop, if I stop fast enough its still reading around 20 and takes a couple of seconds to reach 0. I just replaced the stereo system and didnt know if that would have anything to do with this. Any ideas?

 

[aklim]

I would hook up a scanner to see what the ECM is seeing so you know whether the speedo is lazy or that somehow it is seeing the numbers. I suspect it is the speedo but can't be absolutely sure.

 

[94conv.]

I hooked the gps to it this morning on the way to work and it was matching what the speedo was saying. It may have been an isolated incident. Im going to keep an eye on it.

 

[steverichmond]

I hooked the gps to it this morning on the way to work and it was matching what the speedo was saying. It may have been an isolated incident. Im going to keep an eye on it.

This inspired me to check mine. I did the same thing and checked it again my GPS. Mine is accurate, but I think the GPS updates quicker than the digital speedo on my 93 thus there was a difference of one mph during speed rate changes.

 

[aklim]

This inspired me to check mine. I did the same thing and checked it again my GPS. Mine is accurate, but I think the GPS updates quicker than the digital speedo on my 93 thus there was a difference of one mph during speed rate changes.

When you are going on flat straight lines, is it correct? If so, I would say it is correct.

Another question is does the ECM see the same change as the speedo? Could it be some sort of lag mechanism like the fuel gauge so that when you go around a curve and the fuel sloshes to one side you don't get a lower reading?

 

[94conv.]

When I noticed it being slow, we were coming off a 55mph zone into a 35 mph zone and it was reading like 38 and it felt like we werent even going 25. So then I got paranoid and went out on the interstate to see how it ran with traffic then back to town and I couldnt tell at that point. So then I saw on another thread someone checked theirs with the gps and when I did that it was ok. These cars are 16 years old, it could be connections getting old making it slow, really hard to say. Im going to keep watching it

 

[steverichmond]

Yesterday, the weather was beautiful so I had to get her out. Anyway, I did a number of steady speed comparisons and the speedo and GPS agreed. I think your right the ECM does some type of delay to avoid erratic displays.


Steve