A number of years ago I swapped a 150 MPH SHO speedo head into the cluster. Worked fine for about a year, then it started acting weird. I replaced it with a spare head I had and the problem went away, but it's now back again after about 3 months of trouble-free operation.
The easiest way I can describe the problem is to say it looks like there's a loose wire somewhere and the signal drops, causing the needle to "bounce" around. Sometimes I'll be going 30 or 40 and the needle just sits there at 0 for 10 or 20 seconds at a time. It seems to be most pronounced at lower speeds (40-50 or under, seldom does it at 60 or 70) and only for the first, say, 20 minutes of driving. Both the odo and speedo are affected (when it sits at 0 the odometer doesn't move either, and I've lost 9 miles off the trip odo on the last tank's worth of travel alone).
I thought for sure it was the head gone bad after the problem went away after I swapped it out and put in my spare. Now I'm not sure that's the issue.
I'm wondering if it's a connection somewhere, although it doesn't seem like the speedo bounces are in any way related to road bumps/vibrations.
I am pretty sure the PCM is starting to do weird things (have to wait for the SES light to flicker after turning the key on before starting otherwise it cranks without firing for a few seconds) so I'm wondering if the PCM could be the cause.
The other possibility I can think of is the head has indeed gone bad (again), and I need another replacement. I can always swap the stock 120 in without pulling the cluster out (leaving connections as they are) to try and determine if it's the head or not.
It's not trans/VSS related. The speed signal is good and clean since I've never seen it do anything strange while datalogging. I also have my ScanGauge set to read out speed, and it also is normal.
What do you guys think I should try first?
The easiest way I can describe the problem is to say it looks like there's a loose wire somewhere and the signal drops, causing the needle to "bounce" around. Sometimes I'll be going 30 or 40 and the needle just sits there at 0 for 10 or 20 seconds at a time. It seems to be most pronounced at lower speeds (40-50 or under, seldom does it at 60 or 70) and only for the first, say, 20 minutes of driving. Both the odo and speedo are affected (when it sits at 0 the odometer doesn't move either, and I've lost 9 miles off the trip odo on the last tank's worth of travel alone).
I thought for sure it was the head gone bad after the problem went away after I swapped it out and put in my spare. Now I'm not sure that's the issue.
I'm wondering if it's a connection somewhere, although it doesn't seem like the speedo bounces are in any way related to road bumps/vibrations.
I am pretty sure the PCM is starting to do weird things (have to wait for the SES light to flicker after turning the key on before starting otherwise it cranks without firing for a few seconds) so I'm wondering if the PCM could be the cause.
The other possibility I can think of is the head has indeed gone bad (again), and I need another replacement. I can always swap the stock 120 in without pulling the cluster out (leaving connections as they are) to try and determine if it's the head or not.
It's not trans/VSS related. The speed signal is good and clean since I've never seen it do anything strange while datalogging. I also have my ScanGauge set to read out speed, and it also is normal.
What do you guys think I should try first?
