Tach Problems

[Hunter92]

Has anyone experienced a problem like this?
Here's a video along with a scanguage connected, showing full acceleration from a stop. The engine is shifting at the correct time but the tachometer goes past redline and almost hits the molding.

Normal shifting points occur around 3500 RPM
Idle is at 1000 RPM

 

[Brian757]

I have no clue what that could be. I would take that to a calibration shop and have them fix that for you, or preferably the dealership.
Even though I know your not red-lining, it still made me cringe watching the tach needle soar that high. I would have that fixed asap. Even though I know you have the scangauge, which reads correctly, I don't think I could drive my truck watching my tach do that. I don't know, that is a major mind fu(k.

 

[t4r4life]

wow never seen that before, our rpm gauge is electronic i think not like the old school cable so it might be a ECU issue

 

[Singtoe]

If the scan gauge is reading normal then it is not the ECU.

Tachometer might be crapping out or the ground to it might be suspect.

 

[Hunter92]

Almost every person that I've asked says to check the tach sensor. Is there a sensor? If so, does anyone know where it is? I've looked. I'm also not sure where the ground would be located.

It reads about 1500 RPM's high or even a little more.
When my tach reads 5k its actually at 3.5k

 

[Kurtis]

If the scan gauge is reading normal then it is not the ECU.

Tachometer might be crapping out or the ground to it might be suspect.

Almost every person that I've asked says to check the tach sensor. Is there a sensor? If so, does anyone know where it is? I've looked. I'm also not sure where the ground would be located.

It reads about 1500 RPM's high or even a little more.
When my tach reads 5k its actually at 3.5k

Using the same logic as Singtoe, if your scan gauge is reading correctly you can safely assume that the ECU and sensing unit is not faulty. If it was then your scan gauge would be off as well. I would be looking at your gauge cluster.

 

[Hunter92]

Here's a video that shows the scanguage

 

[Singtoe]

If the scan gauge is reading normal then it is not the ECU.

Tachometer might be crapping out or the ground to it might be suspect.

 

[Hunter92]

Bump

 

[Manic]

Did you ever get this figured out? What did the problem end up being? I'm having the same problem, but mine is fine from idle to 3k, but above that it doubles(estimate) up on the RPMs shown on the tach.

 

[brifri01]

Did you ever get this figured out? What did the problem end up being? I'm having the same problem, but mine is fine from idle to 3k, but above that it doubles(estimate) up on the RPMs shown on the tach.

My 97 does more not working then working but there’s sometimes a jump or two around 3,000-3500.

 

[Manic]

My problem ended up being the ground wire for the diagnostic unit port in the engine bay. The bolt had backed out some.