e30 tacho playing up

[bravo 34]

The tacho on my e30 started to play up today. Moves jerkily through the revs and sometimes appears "caught" at certain revs.

Battery in the cluster is only 1-2 years old.

Dodgy tacho or sensor or what?

Cheers.

[Forrest 35]

Have you checked the plug on the back of the diff?

[dr_sinist3r 0]

my skyline tacho used to play up. it would work sometimes but then few weeks ago just stoped working all together.

i'd put mine down to dry solder cos i opened the tacho up sprayd it with contact cleaner and heated it up with my heat gun for a minute or soon.. cooled it down and it startd working.

what id do first is

-open it up and connect an aftermarket tacho to see if the problem is still ther. if it is then the problem is on the sender unit side. if the problem goes away then we know your tacho is the problem.

[turboprop 0]

Have you checked the plug on the back of the diff?

blonde moment?

[Forrest 35]

Isn't that the speed sensor? actually that would be connected to the speedo. Fail.

[turboprop 0]

my skyline tacho used to play up. it would work sometimes but then few weeks ago just stoped working all together.

i'd put mine down to dry solder cos i opened the tacho up sprayd it with contact cleaner and heated it up with my heat gun for a minute or soon.. cooled it down and it startd working.

what id do first is

-open it up and connect an aftermarket tacho to see if the problem is still ther. if it is then the problem is on the sender unit side. if the problem goes away then we know your tacho is the problem.

The signal comes straight from the ECU, which uses the VR crank angle sensor to determine engine position and speed, if the sensor was stuffed, the car wouldnt run. What im saying is, we can assume the signal getting to it is fine, and its not a sensor fault, unless the ECU is playing up (unlikely).

It seems to be a common problem with E30's, im not sure what causes it, if it is the tacho it self (easy to replace) or the circuit board in the gauge cluster, but dry joints / broken joints are common.

A friends tacho is stuck on 6500rpm

Edited January 2, 2010 by turboprop

[bravo 34]

I'll pull it out and check the plug on the back of the cluster and give it a gentle once over with an air gun.

Then I'll try a spare one I've got lying around.

Thanks turboprop - you confirmed my thoughts about the sensor.

I'll let you know how I get on.

[Silver Fox 43]

I thought the Tacho read off the sensor from the spark plug lead, or is that only on the M40's?

[e30ftw 396]

That inductive pickup is for 2 stage injection AFAIK, m20's have the inductive pickup on the #6 wire. If disconnected, the ECU injects fuel every stroke, instead of alternating strokes (1,3,5 as one and 2,4,6 as the alternate).

[hotwire 352]

my skyline tacho used to play up. it would work sometimes but then few weeks ago just stoped working all together.

i'd put mine down to dry solder cos i opened the tacho up sprayd it with contact cleaner and heated it up with my heat gun for a minute or soon.. cooled it down and it startd working.

what id do first is

-open it up and connect an aftermarket tacho to see if the problem is still ther. if it is then the problem is on the sender unit side. if the problem goes away then we know your tacho is the problem.

Glenn - you watching??

Here we go again with my ..... did this & it was ..... causing the problem. Every car is different!

Graham - The tacho signal IS fed via ECU (signal in turn from low tension) & unlikely to be an ECU problem.

As you say - check dash plug connections but my money would be on fault in tacho - dry joint or similar

EDIT: Or - "sticking" - check needle

Edited January 3, 2010 by hotwire