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96 T100 3.4L Tach problems..

13K views 14 replies 5 participants last post by  BamZipPow  
#1 ·
Hello,
anybody have a direction to point me to a area to look for a problem I am having with the Tach in my 96 3.4L Auto T100? When I start the truck, tach initially jumps up and reads correctly, then slowly settles back to zero @ idle. When I give it gas, needle responds correctly, also reads fine when driving around. When I come to a stop the tach goes to zero. Engine does not change tone or stall, or have any other negative symptoms other than the tach not reading @ idle. I do want to fix this because I am listing the truck for sale and think a interested buyer would not like the situation. The truck runs and drives fantastic apart from this, and has not given me any other trouble. This just started today too.....
thanks for any help.
 
#7 ·
Looking into this issue as well. I have a 96T extended cab 2wd, 3.4 L Automatic. I am having the same issue as described above. It is an intermittent problem. I was wondering if anybody had any pics or could describe the locations where to look for the problems. Any help would be appreciated. Its not a huge problem... but i am a perfectionist, and it drives me nuts:D:D
 
#11 ·
took a look around the engine bay today, and im not 100% sure where to check for the coil grounds. is the ground where the coils sit on the valve cover?

does anybody have some pics or diagrams on exactly where to check?? it would be very very helpful.
 
#12 · (Edited)
The interior ground points should be behind the left and right kick panels.

The engine bay ground points start at the battery, driver side fender wall, the engine one looks to be near the air plenum close to the diagnosics port/throttle body.

Another thing to check is the harness on the back of the combination meter...yes...it means you have to tear things down to check it and the wires as well. It happens... :(

Not sure if you have any aftermarket radios/amps installed or not but the installer could've taken some shortcuts and screwed a screw into the wire harness that might make it tough to detect....but that's probably a long shot.

It would probably be a good thing to hunt down the factory wiring diagram fer yer year. It's come in pretty handy fer me... ;)
 
#14 ·
I replaced my battery recently and decided to clean that ground connection right by the batter as well. So far, so good, i haven't had the tach act funny yet, but it only did it like 3 times a yr so not sure if its fixed yet, but looking like it. The ground connection had paint on it so that could keep it from getting a proper ground. so i sanded it off. so far so good though!!!
 
#15 ·
Glad that worked out fer yah... :D

You might want to put some dielectric grease on there (the stuff you put on the bulb sockets) so you don't have a problem later on...or even running another body ground further up the fender away from the battery. ;)