Tach Fluctuating

[TheCanadian007]

Hello everyone, I've got an '87 Plymouth Horizon with a carb'd 2.2 Sometime around last summer my tachometer began fluctuating and moving erratically.

I tried swapping the cluster out with one from the local scrap yard and I had the same result. Two funky instrument clusters seemed likely, so I posted a similar thread on TurboDodge a few months back. Everyone suggested that the solder points on the back of the tach PCB were cracked and needed to be re-flowed, so I redid all of them and still have the same result.

The tach generally reads around 500 RPM higher than the actual engine speed is and at idle it's really all over the place. Last December my HEP was replaced with a new aftermarket Niehoff (generic manufacturer that Canadian Tire carries), so I doubt that the HEP would've gone bad again, as the engine runs fine; only the tach is wonky. All other gauges in the cluster operate as they should.

So my question is, do I have a bum instrument cluster or what else would be causing my tachometer to behave oddly?

Thanks, TheCanadian.

[TheCanadian007]

Bumpidy Bump

[shelbydave]

It's running good though? My carbed 2.2 did that but it ran like crap while it was happening. I would shut it down, then restart it, and all was fine. A new computer fixed it for me.

[BadAssPerformance]

Solder points are VERY common in the l-bodies, but and connector issues are common tpp and it could be a broken wire somewhere between the coil and computer and cluster as well.

Is it bouncing around or just losing signal and falling? Act worse when it hits a bump?

I hate electrical gremlins

[TheCanadian007]

The car runs fine, it kinda hesitates and misses occaisonally when it's not warmed up, but that is just the glory of carburetors. Once the engine is warmed up it runs fine. Restarting it doesn't help and it doesn't fall and then bounce up; it just flutters back and forth around the RPM that the engine is going at. I don't believe it changes when i hit a bump or when I hit the dashboard with my fist. I'll double check the grounds and maybe try swapping the Spark Control Computer with one from a wrecking yard....

[TheCanadian007]

Bumppp

[mcglsr2]

i had that happen to me for a little on my P body - it did it when i swapped out computers. since then it has stopped. all i did was disconnect the battery then reconnect, let the computer "re-learn." that seemed to work for me as it has not been back since. good luck and i hope you find the issue.

[CDNTurboZ]

Bumppp

If you want to try another cluster I might have a spare kicking around...

[TheCanadian007]

O rly, thanks! Where abouts are you in Winnipeg anyways?

[TheCanadian007]

bump.... CNDTurboZ.....?

[CDNTurboZ]

sorry about that I forgot about this post lol, pm sent.