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View Full Version : Jumpy tach


Strahan
03-26-2009, 07:52 PM
I've noticed sometimes when I let off the gas my tach surges around. Sometimes it jumps a few times, sometimes it's just once. I had my camera handy today so I caught it doing it: http://www.nischan.com/temp/MOV05833.MPG. The bigger jump around 0:20 is when I shifted, but the rest of the time the throttle was smooth, I wasn't pegging it to cause the earlier on tach motion.

I'm not particularly worried, but what would cause that? A sensor or something?
LX-incredible
03-26-2009, 09:43 PM
An ignitor on it's way out, or a bad connection/ground.
Rendon LX-i
03-26-2009, 09:44 PM
or your dizzy
3rd Party
03-26-2009, 10:19 PM
heh, time to download the shop manual and find the wiring diagram to see where your tach gets it's reading from, along with it's power supply and ground!
1ajs
03-26-2009, 10:33 PM
sounda like the voltage is bouncing either a loose wire somewhere or the tach needle is getting finicky and needs replacement
3rd Party
03-26-2009, 11:04 PM
heh, time to download the shop manual and find the wiring diagram to see where your tach gets it's reading from, along with it's power supply and ground!

x2
1ajs
03-26-2009, 11:12 PM
x2

why u quoting urself ?
3rd Party
03-26-2009, 11:26 PM
because what i'm saying seems to make sense...you check where the tach draws it's reading from, along with where it gets it's power and you're set?
LX-incredible
03-27-2009, 08:22 AM
It's the ignitor or a connection/ground at the distributor. A break in the blue coil wire, which also directly connects to the tach wire through the coil, will not cause an upward jump in the rpm like that. When ignitors start to fail they usually "break up" the signal to the coil, which causes the tach to jump due to the increased coil firings.

This happens mostly after you've been driving for a while, correct?
2oodoor
03-27-2009, 01:34 PM
^^^^ he is almost always right on the money
:D I concour
stat1K
03-27-2009, 02:24 PM
^^^^ he is almost always right on the money
:D I concour

lies!

but yeah it's true... i'm having the same problem on my civic, only i've changed ignitors and other parts as well and my problem seems to be my tach connection because it's not the oem tach.

it's probably your ignitor as it's the most common cause of this problem.
lostforawhile
03-27-2009, 02:43 PM
it's probably your ignitor thius is usually what happens when it's going out ,it causes multiple sparks like an msd which confuses the tach
Dr_Snooz
03-27-2009, 07:58 PM
If memory serves, Rock Auto had Beck Arnley ignitors for like $50 not long ago.
LX-incredible
03-27-2009, 10:31 PM
You'd be better off with a junkyard oem ignitor than that chinese bullshit anyday.
lostforawhile
03-28-2009, 05:45 AM
You'd be better off with a junkyard oem ignitor than that chinese bullshit anyday.the beck arnley is one of the better ignitors,thats what nappa carries or used to.
Dr_Snooz
03-28-2009, 07:55 AM
So you know this is coming...

Why does my tach go all crazy when I'm cranking it over in the morning.
MessyHonda
03-28-2009, 04:41 PM
what if u dont have an ignitor like i do?
guaynabo89
03-30-2009, 02:17 PM
what if u dont have an ignitor like i do?

you do. its inside the distributor.
'A20A3'
03-30-2009, 03:05 PM
you do. its inside the distributor.

correct
MessyHonda
03-30-2009, 07:01 PM
you do. its inside the distributor.

nope...i gutted my distributor....i did a ignitor bypass...no more msd fired ignitors
Rendon LX-i
03-30-2009, 07:12 PM
i took my bros ignitor or coil in the inside out and put the two black wires togethers and the white wire also to the white and red wires on msd...is that what you bro
MessyHonda
03-30-2009, 08:48 PM
yeah but i did this
http://www.3geez.com/forum/showthread.php?t=56779
guaynabo89
03-31-2009, 01:26 AM
nope...i gutted my distributor....i did a ignitor bypass...no more msd fired ignitors




Maybe your problem is just the tach. try running the rpm output of the msd to the tach and see if it stops. If yes then its probaly a ground or something odd like that. wouldnt hurt to keep it wired directly to the msd though
lostforawhile
03-31-2009, 04:28 AM
Maybe your problem is just the tach. try running the rpm output of the msd to the tach and see if it stops. If yes then its probaly a ground or something odd like that. wouldnt hurt to keep it wired directly to the msd though
wait you are running an msd with your factory tach? of course it doesn't work, you need a special box between the tach output and the input of the tach. this has always been a problem with a lot of tachs and msd boxes. some tachs work right,and some don't
guaynabo89
03-31-2009, 05:52 AM
No Im not running a msd at all anymore. it took a crap. I have no problems with the tach.
lostforawhile
03-31-2009, 05:54 AM
i was going to say if you had a factory ignitor, you could just tie into where the original ground wire went to the coil,before the box, this probably would work,then it would be reading rpm from the ignitor like the original setup
Strahan
04-01-2009, 11:56 AM
Thanks for the tips guys. Sorry for the latency in reply, been too busy lately hehe. I'll give it a shot and see how it goes.

Thanks again!
MessyHonda
04-02-2009, 07:23 AM
Maybe your problem is just the tach. try running the rpm output of the msd to the tach and see if it stops. If yes then its probaly a ground or something odd like that. wouldnt hurt to keep it wired directly to the msd though



yeah i need to beef up my grounds again...i just wanted it to run so i didnt go back and take my time