The tach on my 87 944S doesn't seem to be working right.

In 5th gear, I would sometimes need 3600 rpm to go 70mph, and sometimes I would need 4200 rpm to go the same speed. The user manual has a graph that shows 5th gear to need 3500 rpm for 80mph!

Tested my clutch, it's not slipping, and doesn't produce any burning smell. Speedo also seems right, judging from the relative speeds of the rest of the traffic.

So prime suspect is the tachometer. But the workshop manual only has test procedures using the 9288 tester. Any DIY method for testing the tach/senders?

 

No clue.. Palo Alto Speedo might be able to help. Give them a call.

 

Hay maybe all your problems are the speed reference sensor.

At 70 i'm only at 2800.

Just a thought.

 

hook up an external tach, triggered by a spark plug wire, some timing lights have a tach function, and compare readings with tach in dash. I cant think of any other way to check the tach, but you could check the speedo calibration. It would require an empty or lightly travelled road and a stop watch. Set speed to 60 mph and measure time from one mile marker to the next. Speedo is usually slightly optimistic and will read a couple of mph faster than you are travelling.

 

UUTQ, how do I test the reference speed sensor??

MHT, I will shop around later after work....

I have been toying with the idea of getting the G-Tech Pro Competition, which will give me an accurate speed, and a tach (but I don't know how accurate the tach is)