another bouncing tach,also noise from under hood

[deadflo]

I experienced the infamous bouncing tach issue this weekend. It occured when I was stopped at idle, with the tach needle bouncing all over the place. When in gear and driving it was minimal.

I then noticed a "whirring " noise from under the hood near front of the engine. It appeared the noise occured exactly the same time as the tach bounce.I suspected it was from the dizzy, but im not sure. I pulled the cap and rotor off, didnt seee anything obviously amiss though.

Note I DO Not have pertronix, just stock ignition system.

Any ideas? I note some foks said they were able to get their tachs fixed for about 50 bucks. Wonder who works on such items?

[bemmerguy714]

My tach is bouncing all over too! Would I just have to replace it completly? :stupid:

[deadflo]

This has been a common topic, I don't hink anyone really knows whats going on although theories center on connections at the coil, the dampening oil in the tach, or incompatability with aftermarket ignition systems. In my case it is definitely linked to some weird noise from the front of the engine.When the tach jumps around, you can hear the noise. When the noise stops, the tach is OK.

I havent had time to re-eximine it. I have a mechanic in mind who has owned several Z's I will try to have him look at it in the near future.

[deadflo]

I had a chance to drive my Z over to the shop i mentioned but the owner (and z expert wasnt there). However another guy there said he belive the buzzing noise to be originating from the dizzy as well.(bad bearings?)

Again the tach is only bouncing when the noise occurs.

Although she is ruinning OK now, I figured I'd order another distributor.You think it could go out completely soon?

Whats everyones opinion on replacements? Are the rebuilt units Motorsports and VB carry ok???

Please remind me what the deal is with the alignment of the unit when you replace it that is shown incorrectly in the service manuals...

[SavannahZ]

Mine had the exact same problem awhile back. In the end it turned out to be a poor connection I had made to the ignition module after doing the ZX upgrade.

It did what you describe. The noise and poor running only when the tach bounced. My car got to the point where it would stall and then start and stall repeatedly.

Simply retwisting the wire and tightening the connection made it right.

Hope this helps,

Jonathan

[EScanlon]

AFAIK the only connection to the Tach from the Dizzy is through the coil, as that is where the leads (both of them) from the tach end up. I would definitely question any electrical connections you have recently made / repaired / changed or in any manner is different from when the car did NOT make noise.

Aside from that, if you are running the true-blue original system, then you are running points, condenser and rotor. There are various items there that would definitely affect the tach's operation. If the points are starting to arc and make poor contact because the dwell is off or because the points are pitted etc, then the coil wouldn't discharge and you would sense a "miss" at the tach.

Is your resistor still functional and not corroded at the connection points?

Ask Bambikiller (Carl) and HLS-30 (Will), they're bound to have better guesses than my WAG. I'm not an engine mechanic, I do bodies. But before you opt to replace, make sure that it can't be traced elsewhere.

Enrique

[deadflo]

It was the distributor.

Replaced it, the buzzing stopped, and tach works like new.

When I had the dizzy out you could spin it by hand and it made the buzzing noise.

[EricB]

geez... how much did a new distributor set you back? - Mine's an '81 ZX unit.

The same thing started happening to me right as I pulled in to Monterey Historics on Saturday morning. Did it a couple more times on the way back home to Los Angeles on Sunday... great....

I did a search for distributor rebuild and didn't find anything.

Does anyone have any added tips on rebuilding them? To me the "buzzing" sounds like it would be coming from a bearing that's all out of lube... My $0.02

-e