bouncing tach?
 

Here's my problem:
While driving, my tachometer is bouncing. The RPM gauge on my VAFC & AVC-R are not changing like the tach is. At idle the tach doesn't bounce, and reads the same as the other guages. What is going on? Where is the tach getting this strange reading from?

Here's some recent info on what i'v done lately:
2 nights ago, i was able to get my car street tuned at 7psi with the VAFC. I was pretty satisfied the way Low throttle has been tuned, but WOT isn't completely tuned yet. I've noticed some serious boost creep at WOT.... it's max holding at 1 bar on the AVC-R.

Last night i left a parking lot and started driving, about a half mile down the road, the battery died while moving. I got it jumped, but it died a few seconds later. I then got a new battery and some new spark plugs. The car started up and i was able to drive fine. But, when i looked at the tach, it was bouncing up and down between 3k & 4k when i was driving at about 3,000 RPM's.

does anyone have any idea what is going on?

Re:bouncing tach?
 

Ever since I switched to OBD1 from OBD2, my tach's done the same after 6000 RPM. I think it's something in the distributor. Possibly the internal coil gone bad. I'm going to switch to an MSD type ignition and see if that changes, because when I had an AFC, the RPM on that was steady as well.

Re:bouncing tach?
 

mine doese that after 7 but then it just stopped on day :)

Re:bouncing tach?
 

have your alternator tested.

Re:bouncing tach?
 

Ground?

Re:bouncing tach?
 

is this an after market tach? i had a problem similar, and the ground wire was loose

Re:bouncing tach?
 

it is not an aftermarke tach..... it is a gs-r tach added to my LS cluster. It has worked fine for over 2 years.

since i first posted, i started the car back up, and drove it around a little more. whenever the tach started to bounce, the car started to run like crap. i tried switching ecu's .... adjusting the distributor, and checked grounds. i then got real frustrated and decided to beat the ---- out of it, so i floored it a couple of times, and the problem went away!?

i started driving around some more, and things were fine for narrow throttle (below 60%). i then started to tune for High throttle, and nothing i could do could keep it from lean popping and going into limp mode.... i tried running richer, but the car kept running progressively worse. I felt something was wrong so i started driving home..... it didn't make it the whole way. now the car will not start. i have a feeling it has something to do with timing or spark. I think i may have fazed out my sparkplugs. to make things worse, I can't pop the hood now! So, now i have two questions..... if you can't pop the hood with the hood latch, how can you un-latch it? and why won't my car start?

i'll try to answer any questions if you can help me get to the bottom of this ------- caper.

Re:bouncing tach?
 

dam sounds like what mines doing also but mine still runs but it cuts out and ---- when it starts bouncing around.

Re:bouncing tach?
 

Check the Tach signal wire in the Dizzy, its conected to the TDC censor also, so if it burns up or grounds out somewhere internaly, it will let the car crank but not start, Have this wire checked out for cont. from the dizzy to the ecu and the cluster.
Also if you have multiple devices tagged to the tach wire, it will draw to much away from the guage.
thats my best guess.

Bryan