Civic LX, with a jumping tach (steady idel) that started to have stalling issues. I replaced the ICM and the stalling issues went away but the tach is still jumping? Isn't that tach controlled by the ICM? Any ideas?

 

Ohm test the blue tach wire attached to the ICM.

 

Check the CFK wires attached to the timing belt cover. It runs down from the harmonic balancer up around the alternator. Make sure that is still intact. If there is any sign of damage, you may have shorted out the tach in the cluster. Happened to me after doing a timing belt change. I forgot to secure the sensor wires on the cover and the alternator belt chewed through it.

 

The wires are intact 09 chaplak.

RonJ, how do I ohm test a wire when I can only access one end of it?
Do I ohm test from the ICM to the distributor pig tail?

 

You have access to both ends - ICM and gauge cluster connector.

You can ground one end of the wire and test continuity to body ground to look for an open.

You can unplug both ends and test for continuity to body ground to look for a short.

 

Update: I just noticed a stutter in the idle at around 35mph. It kind of felt like misfire, but no CEL. I was able to duplicate the incident a couple more times, no CEL. I am thinking that is may be spark related? Good compression, 40psi fuel pressure. So maybe the tach is reading correctly???

 

How do you know there are no CEL codes?

 

coil and icm will strand you eventually if you dont carry spares and tools.
jumpy tach is classic bad icm symptom.
be prepared is the boy scout's marching song.

Advanced Ignition Troubleshooting - Team Integra Forums - Team Integra

Starting Problems

 

I have been scanning the OBD system and there are no codes being thrown. Good advice tamboo.

So I was being lazy doing some testing and put the distributor back on with only the TOP bolt holding it and went for a drive... NO MORE JUMPY TACH!!! That must be a coincidence, so I reinstalled the front bolt and took for a drive, The tach was jumpy! Again I took out the other bolts and again, NO MORE JUMPY TACH! 5 test drives later and still NO jumpy tach! How is this possible?

 

Does jumpy tach equate to engine misfiring/running poorly or does the engine run smoothly when tach is jumping?

 

I thought that the jumpy tach was unrelated to the RPM of the engine just because it was SO sporadic. However, I listened very closely and discovered that there was a correlation. Driven the car 100 miles now and still no jumpy tach or rpm, but mild shutters (misfires) when holding a low speed (35mph).

 

Just to finish this thread, the shutter at 35 was tire related. I replaced the distributor and never had an issue with the jumping tach or RPM again.