So my tach still jutts up and down every now and then, it is quick but it happens frequently once it gets started. I cant notice any significant cutting out or bogging of the engine...(at least not that I can hear/feel) happens on accel and decel.

Mystery: (Replaced)

Fuel pump, filter, filler neck, fuel lines
Distributor, cap, rotor, ICM
Spark plugs, wires

all within the last year! Before it would flat out just cut out...but thats because there was corrosion in my distributor cap. Got that all fixed. Now it seems as if the most it will "jutt" is 500 rpm max. And I may be wrong but I cant notice anything out of the ordinary beside the tach needle. I know for a fact that there is a short in my tach cable on the other side of the firewall...but I think that it would do it much more frequently if that was the case.

What else could cause this?

 

Normaly a bad/loose plug, wire or blown out cap will cause that.
I have also seen a chaffed power wire to ground cause it.
Even a new plug or wire can be bad. Ohm check the wires.
Or a tach filter on the power wire.

 

I had mechanic check the wires and all and said they read fine. When I completely put a brand new ingintion system in, I made sure and used the best parts, Ac Delco plugs, wires etc. so even if a plug or wire is bad...im not going to spend another $100 plus dollars to replace all that and then have it do it to me again. I can almost gaurentee that its not the plugs/wires. I cant hear or feel a single thing when it happens.

I have a 91 Trans am, and after reviewing info on other threads, there have been problems with 90-92 tachometers...not sure what it could be thats causing this or why...

If it is just the tachometer fluttering from time to time...im ok with it, however if it is something that is faulty/bad I would be uber pissed seeings how I have a brand new ignition system.

 

Good to know you used good parts. These car did have some problems with factory tach filters.

 

mine has done this for 3 yrs now. where is the tach filter located? where can you buy one? lol

 

Bad distributor module maybe?

 

I replaced a module and it fixed that, Also fixed a misfire I was having at high RPMs too.

 

changed engine during swap and used all new dizzy. problem wasnt so bad but still jumpy. then 2 months later its back to being all over the board...