I have a stock 91 si hatch that I just bought a week ago and when I rev it past a certain threshold (usually around 3-4k rpm) the tachometer needle just starts jumping around all over the place lol.

It seems to be just the tach, cause the engine is running fine.
Before I go out and buy a new cluster, I'd like to see if there are any easy fixes to this.
I tried searching but couldn't find anything with my exact problem.

Thanks for lookin.

 

Sounds like the ignitor in the distributor is dieing. Pretty common on these cars.

 

Pull the cluster out and there will be a ground wire on the back held on with a Philips head screw make sure that is tight. Clean around the contact area as well with like a baby wipe.

 

Wouldn't that make the car run funny too?
The engine isn't revving all over the place, just the tach needle.

OK cool, I will try that. I figured that might be the issue.

 

Yes when mine went out on my it was backfiring through the intake manifold and mine would rev for a sec and then just die.

Make sure there isn't a break in the blue wire going to the distributor as this is the tach signal wire.

 

OK cool thanks I'll check it out!

 

ya the the ignition control module in the dist. when mine was going out the only thing that was actually acting up was the tach needle. i then swapped with a known good ignitor and sha boom! problem solved

 

the ignitor fails in stages. jumping tach is just a warning. itll fail completely eventually.

you can check grounds, or even clean the contacts at the back of the cluster, but its probably the ignitor that needs to be replaced.

 

get your alt tested too. could be because of lack of propper voltage being sent from the alt

 

It is the ignitor. I had the exact same problem in my CRX.
Take the dizzy cap off. The ignitor is right there, it has two wires connected to it. Mine was held in by 4 stripped screws... Just get one from a junk yard, or a new one for around $100 i think.

 

is it #8 or #12

 

Its #12 on that diagram. Good luck some times people strip the hell out of those screws.

 

#12 = COIL
#8 = Ignitor

 

yeah you replace the coil when theres no spark at all. that fails pretty often too.

 

what about when the speedometer needle jumps and rattles in the cluster.?

 

you either have a broken speedo cable or the gears in the acutal cluster ar going bad. i did a b16 to my last ef and when i tried to hit vtec it wouldnt engage. when i took the speedo cable out of the back of the cluster i noticed it was ground down to a smooth surface. it should be square shaped.

 

alright im gonna bump this as im having an issue.

I was told/read from someone else that the reason my tach is jumping randomly and not the engine as well and every once in a while the engine back firing through the intake like dephtone stated, that it could be the ignitor is failing...But I just replaced the Distributor today and it's still doing it. Granted the distributor is a re-manufactured unit from advanced auto parts and i've heard of people getting shitty reman parts from advanced/auto-zone but how likely is that to have happened?

 

Check your distributor it could be the problem either or the alternator.

 

check your grounds as well.

 

I had a jumping tach once and it jumped at the same spot (3-4k rpm) all the time. I did not have anything faulty other than the tach itself, the dizzy was replaced with a new one but the problem persisted. I replaced the motor (not to fix the tach) and the tach still jumped around. I replaced the tach and the problem went away.

Sometimes, it's as simple as that.