91 4.0 Tach Inaccurate

[Kadams87]

I have checked grounds and am out of ideas. My tach is extremely inaccurate under 3k rpms at which point it slowly becomes closer what seems reasonable. Has anyone experienced this. I had this trouble with the factory 2.9 also. I did a complete wiring harness as dash swap from a 4.0 ranger so all the gauges and wiring are factory. Any Ideas would be appreciated.

 

[swynx]

Did the tach somehow get spun? And the retention rate is higher at the top end. Had a similar problem with an aftermarket tach that my little brothers spun forwards about 9 times.. Try hooking up an aftermarket one

 

[Kadams87]

Factory cluster in both the 2.9 and 4.0 dashes, same problem. Aftermarket tach is how I know the tach in the 2.9 was off. 4.0 is playing the same way so I am figuring the same issue. The only aftermarket tach I have is a huge Autometer that is slated for a more worthy recipient.

 

[swynx]

Try tracing the wire? And just replace anything in between. Simplest solution would be aftermarket tach. But it seems silly to have 2 tachs. Have you replaced the ignition source. Been awhile since I've been under the hood. I.e. Ignition coil?

 

[Kadams87]

Try tracing the wire? And just replace anything in between. Simplest solution would be aftermarket tach. But it seems silly to have 2 tachs. Have you replaced the ignition source. Been awhile since I've been under the hood. I.e. Ignition coil?

I would like the tach in the dash to work correctly, If this were a track truck then I would put the autometer in no problem. This one goes to work and back. 4.0 has EDIS and it's a new pack...problem existed before I changed over to the screamin demon.