I have found countless threads on here about tach problems but none that I could find that applied to my set-up. I have an '88 2.8L V6 with cranecams fireball ignition coil, and their HI-6 ignition module. Tach worked great for a couple years then got a little off. When it finally just lost its mind - 5500 at idle and pegs out as soon as you touch the gas- I replaced the pick-up coil and the "ignition control module" that are inside the distributor, but it made no difference.

Is there a pre-set order of things to do to diagnose the culprit short of taking out my cluster and buying a new one? If I have to buy new I will, but if there is a simple way to correct, I'm all for spending that money on something else on the car.

Thanks.

 

tachs go bad over time, some faster than others. something about capasitors getting weak.

I went through 4 tachs on my v6 trying to find one that worked. I got lucky enough recently to find somebody that was parting out a V6, and he sent me a video of the tach operating before I bought it. Installed it in my car, and it was perfect

I actually bought a brand new tach off ebay a year ago... new in the box, and it was worse than the one I took out of my car... terrible.

just for the record, you can use a V8 tach, it will just read a little low. I saw one on ebay for $20 recently, and it went unsold. shocking

 

I would not recomend installing a V8 tach in a v6 car. The exact problem you are trying to fix would still exist,.... only in reverse ( low reading rather than high reading. )

The V6 distributor would only send 3 signals per revolution rather than the 4 pulses per revolution that the V8 tach is expecting. This would lead the reading to be off - significantly. You'd be looking to replace it with the correct tachometer right after installing the V8 version.

P.S. A signal converter could be installed between the tach and the distributor to correct the number of pulses the tach reads, but the expense of the converter ( about $80 for a new one ) is greater than the expense of simply buying the correct replacement part !

 

well, he did say his current tach peggs when the car is running, so effectively, it's totally non functional

when I had the V8 tach in my car it read 1700RPM at 70MPH in 5th gear
my working V6 tach reads 2600RPM on the highway

I'd rather have the v6 tach, but at least the V8 tach doesn't peg, and he can use it until he finds a v6 tach that actually works, then resell it

 

Where would I find replacement tachs that aren't used for under $80?

 

I buy used parts,..... you'll have to search for new stuff !