Speedometer Jumping - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

Welcome to LS1LT1.com/LS3forums.com - please click here to register...

 
LinkBack Thread Tools
post #1 of 13 (permalink) Old 02-01-2013, 01:01 PM Thread Starter
Regular Member
 
avoctane's Avatar
 
Join Date: Jan 2011
Location: Weslaco, TX
Posts: 277
 
Send a message via AIM to avoctane
Speedometer Jumping

I recently purchased a 99 Trans Am WS6.. I will post pictures & info on it in another thread..

Some Specs for diagnoising my problem...
LS1 Stock Engine
6 Speed Tranny
3.42 Gears
Original Speedometer

When I am driving from 40+ mph my speedometer starts to jump UP & DOWN within a 5-10 mph range... (Tach has no problems - Just FYI)

I read online the ALTERNATOR was going out (which it was) so I just replaced it. I installed a Remy New Alternator - 102 Amps Part No 91524.

And my speedometer is still doing the same thing... What could it be? Any diagnostics or tips would be very helpful, thanks!

avoctane is offline  
Sponsored Links
Advertisement
 
post #2 of 13 (permalink) Old 02-01-2013, 06:34 PM
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 11,536
 
Need to put car on a scanner that does real time sensor data. One of the readings you can view will be what speed the pcm is seeing from the vss. If the reading on the scanner fluctuates like your speedo, then theres a problem with the vss, it's wiring to the pcm, or the pcm. If the reading the scanner gives is correct and the speedo is off then the problem lies in the speedo itself, or the wiring from pcm to speedo.

Common problem with electronic speedometers is the circuit board inside going bad. One of the first symptoms, many times is a needle that jumps around.

Last edited by cocobolo95; 02-01-2013 at 06:37 PM.
cocobolo95 is offline  
post #3 of 13 (permalink) Old 02-02-2013, 09:22 AM Thread Starter
Regular Member
 
avoctane's Avatar
 
Join Date: Jan 2011
Location: Weslaco, TX
Posts: 277
 
Send a message via AIM to avoctane
thanks coco, i'll see if i can borrow one from a friend locally and i'll update you & everybody else here in-case someone else bumps into this issue... I have searched online for this issue for a while now and nobody ever seems to put the answer to the fix...

I'll make sure I do.

avoctane is offline  
post #4 of 13 (permalink) Old 02-02-2013, 09:42 AM
Supporting Member
 
GaryDoug's Avatar
 
Join Date: May 2012
Location: Florida West Coast
Posts: 771
 
If you can't find a scanner locally and you have a pc that can be put in or very near the car, this one will work: http://www.amazon.com/ScanTool-423001-ElmScan-Diagnostic-Software/dp/B002PYBZJO
There are cheaper Chinese-made ELM327-USB ones, but you would have to get good software to go with it, since the supplied software will not be adequate. I can tell you how to do that if you need it.

Another possibility is to use an Android-based phone and get the Torque-BHP app and a Bluetooth adapter: http://www.amazon.com/Soliport-Bluetooth-OBDII-Diagnostic-Scanner/dp/B004KL0I9I/ref=pd_sim_auto_9
It will be slower than the USB versions but should do what you need if the fluctuations are not too brief. That method will require some learning of the app and some possible assistance. Again, I can help if needed.

98 Trans Am, LS1/A4, all stock, original owner
GaryDoug is offline  
post #5 of 13 (permalink) Old 02-04-2013, 03:22 PM Thread Starter
Regular Member
 
avoctane's Avatar
 
Join Date: Jan 2011
Location: Weslaco, TX
Posts: 277
 
Send a message via AIM to avoctane
Garydoug I will order that today cause I don't know anybody who has a scanner, and I might as we'll have it for the future as we'll since I will be keeping this car. I will update the thread as soon as I get it and scan the car. Thanks again!

avoctane is offline  
post #6 of 13 (permalink) Old 02-04-2013, 05:01 PM
Supporting Member
 
GaryDoug's Avatar
 
Join Date: May 2012
Location: Florida West Coast
Posts: 771
 
If you are buying that exact one and need to fill out the $25 for free shipping, I would recommend the ($4) 15 foot USB extension cord, as the one on the tool is only 5-6 feet long and it would sometimes be handy to put the pc outside the cabin.

98 Trans Am, LS1/A4, all stock, original owner
GaryDoug is offline  
post #7 of 13 (permalink) Old 02-13-2013, 08:41 AM Thread Starter
Regular Member
 
avoctane's Avatar
 
Join Date: Jan 2011
Location: Weslaco, TX
Posts: 277
 
Send a message via AIM to avoctane
Coco & Garydoug, I went ahead and purchased that OBD2 scanner from amazon and ran the program w/ the dashboard view while driving last night. The refresh rate was a little slow but enough to tell that the PCM is increasing on the MPH normal. So the issue lies between the speedo itself, or the wiring from PCM to speedo correct?

Are their any other tests to further diagnosis the speedo itself or the wiring from the PCM to speedo?

avoctane is offline  
post #8 of 13 (permalink) Old 02-13-2013, 10:07 AM
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 11,536
 
if the vss is sending the correct reading to pcm then your most likely suspect is the speedometer itself. The circuit board inside is probably going bad. Time to find a replacement instrument cluster.

I see them fairly regularly on craigslist, here in Florida, don't know how your area will be. Try this salvage yard search engine. All the yards ship parts so if you don't find one nearby, branch out to your whole state, region, or entire country.
Car-Part.com--Used Auto Parts Market
cocobolo95 is offline  
post #9 of 13 (permalink) Old 02-14-2013, 06:54 PM
Regular Member
 
Join Date: Jul 2010
Location: South Texas
Posts: 61
 
had the exact same problem a few months ago on my 99 camaro. v6 auto by the way. the speedo would work one second then start jumping all over the place the next . by any chance does it also drop to zero likes its not working then goes back to jumping?mine would work ,not work start jumping around etc,etc. Well anyways i went under the vehicle on the passenger side and saw a wire going up the side of the transmission and couldnt see the connector but i believe that to be the vss. i was going to replace but couldnt even put my hand to reach it or see it for that matter. got pissed just wiggled the wire for the hell of it and speedo been working perfectly for four months
Jrsgalaxy is offline  
post #10 of 13 (permalink) Old 02-16-2013, 08:29 AM Thread Starter
Regular Member
 
avoctane's Avatar
 
Join Date: Jan 2011
Location: Weslaco, TX
Posts: 277
 
Send a message via AIM to avoctane
coco, i would really like to keep my Original Mileage from my speedometer.. I think I read online that people can re-program a speedometer to whatever # you want... Maybe I can use that to re-program the new one to my original mileage?

jrsgalaxy, my speedo never drops to 0. It just moves up & down after 40 mph and i've noticed that when im on a smooth road it doesn't do it as much, and when im hitting a bumpy road it moves up & down much more. (night & day difference)

Maybe a part inside the speedometer thats broken?

avoctane is offline  
post #11 of 13 (permalink) Old 02-16-2013, 12:23 PM
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 11,536
 
I believe cars with digital odometers need special equipment and a program to change the reading. But do a google search to make sure I haven't forgotten the correct info.
cocobolo95 is offline  
post #12 of 13 (permalink) Old 02-23-2013, 09:40 PM Thread Starter
Regular Member
 
avoctane's Avatar
 
Join Date: Jan 2011
Location: Weslaco, TX
Posts: 277
 
Send a message via AIM to avoctane
Talking

To coco, Gary, and all... I have figured out the resolution to my problem so if anybody else has this happen to them they may fix it as we'll.

My resolution to the problem was doing a tranny fluid change. I used 4 qrts of Dex 3 ATF Valvoline. It's been a week since the fluid change and it hasn't happened again, btw it's my daily driver so i really kept an eye on it!!

The tranny fluid change corrected the speedo jump and butter like shifting now!!

I thought I'd share cause I've read lots of threads here that have helped me in the past and i would like to give some help back and to others... Thanks again!!!

avoctane is offline  
post #13 of 13 (permalink) Old 02-24-2013, 05:50 AM
Global Moderator
 
cocobolo95's Avatar
 
Join Date: Sep 2008
Location: Fruitland Park,Florida
Posts: 11,536
 
That just goes to show us how something seemingly unrelated can cause a problem.
cocobolo95 is offline  
Sponsored Links
Advertisement
 
Reply

Bookmarks

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome