Crazy Tach

[92 LX]

Would any of you guys know why my tachometer reads 2700 rpm when my engine is idling at 900? On the way home today, it stayed there, then revved up to about 4gs while I was accelerating (5 spd) then after I shifted, it went back to 2700. It dropped back to normal right before I got home, and behaved after that. I'm thinking a loose connection (or maybe a ground) but any idea where to check? The engine runs fine, but this is annoying. It just started today. Anybody?
'92 LX 5.0 5 spd

 

[Noobz347]

OEM tach?

Any ignition system mods?

 

[wythors]

This is actually a fairly common problem that I've never found a fix for. My wife's car started doing that right after we got it. I scoured the 'net and couldn't find anyone that had fixed the problem. I checked all the connections. I paid for a couple of hours of diagnosis at my local Mustang shop. Nothing. I replaced the tach and no more problems. Since I have three Foxes, the next time I was at the bone yard I spent $20 and bought an extra cluster to have a backup.

 

[92 LX]

Yes, factory tach. Only an aftermarket coil.

 

[92 LX]

Hmmm,
A buddy of mine has an extra cluster. Maybe I can snag the tach from him. Still I'd like to try and fix mine. Seems the gremlins are appearing as she's getting old.
twenty this year as a matter of fact. I'm going to have to post a pic to replace the "?" now that she's gotten a much deserved facelift. Nice Calypso green Wythors. I ALMOST bought a '92 Calypso green vert. instead of my Emerald Green hatch. The hatch had too many more mods, and $3k less.

 

[Noobz347]

Hmmm,
A buddy of mine has an extra cluster. Maybe I can snag the tach from him. Still I'd like to try and fix mine. Seems the gremlins are appearing as she's getting old.
twenty this year as a matter of fact. I'm going to have to post a pic to replace the "?" now that she's gotten a much deserved facelift. Nice Calypso green Wythors. I ALMOST bought a '92 Calypso green vert. instead of my Emerald Green hatch. The hatch had too many more mods, and $3k less.

If you plug in the other OEM tach and the problem goes away then I'd say reviving yours would likely be cost prohibitive.

 

[92 LX]

Yea, I agree. I was hoping somebody would know where the ground was so I could just check that first, but I guess you already went thru that. Thanks for the tip. You guys (this forum) are the greatest.