[DMCForum] Re: Tach Twitch

[doctorDHD@xxxxxxx]

Ryan,
 
My tach also twitches a bit at around 3000 rpm even with the resistor in  
place that prevents the twitch at idle.  I have replaced the ignition coil,  
pulse coil and ECU with no change.  (The ECU and ign coil were used parts.)  What 
are the chances that one of those used parts has failed in the same mode as  
my originals?  What else is left in the circuit besides wire??
 
 
With regards to measuring the voltage at the ( - ),  white/slate  WS  side of 
the coil, you can't just do that accurately with a regular  meter because 
there is a complex waveform signal there.  That being said I  just went outside 
to check it myself and on both AC and DC scales the voltage  reading on my 
digital meter does increase even after 2500 rpm on my  car.  So while the actual 
reading may not be accurate, it seems that the  your lack of upward trend after 
2500 may indicate a problem.  What coil are  you using?
 
Dave Delman
D² & 6530 (+2700 ohms)
 

Tach  Twitch
Posted by: "Ryan Wright" ryanpwright@xxxxxxxxx  ryanpwright
Date: Sat Sep 2, 2006 4:14 pm (PDT)

Short  story: My tach has recently started "twitching". It seems worse
above  3000rpm. Doesn't matter if I'm moving or stationary. The tach
will move up  ~300rpm briefly, then drop back down.  No change in the
engine, it  seems related to instrumentation (though I don't think it's
the tach  itself; the twitch is present all the way back at the idle
controller, so  unless the tach is feeding back on the signal from the
coil, I'd guess this  problem is with the coil, idle controller, or
something else on the  line).

Any ideas?


...  except for one point: The
connection to the coil (I made this on the  white/grey wire connected
to the ECM) is supposed to increase voltage as  engine RPM increases.
This is true up until about 2500rpm; adding  additional throttle and
increasing the RPM actually causes voltage to begin  dropping. I'd
think it should keep going up? 

 


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