funky tach readings - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


General Miata Chat A place to talk about anything Miata

Reply
 
 
 
LinkBack Thread Tools
Old 08-31-2010, 10:19 PM   #1
Junior Member
Thread Starter
iTrader: (3)
 
frostyllama's Avatar
 
Join Date: Feb 2008
Location: Pollock Pines, CA
Posts: 281
Total Cats: -2
Default funky tach readings

i adjusted the idle on the TB and i had it at about 700 and it after a couple of starts it came down to the picture bellow. occasionally the tach will jump around in about 300-500rpm increments unprovoked, some days it will read 4k @ 65, other days 3.5k. wiring, tach, cas, TB? i don't think it has anything to do with the clutch because i did the full throttle at 40 in fifth test with no slipping (referring to the 3.5k 4k variation.) i'm pretty sure the o-ring on the cas is fried so i'm going to start by replacing it.

i just wanted to know if this was even possible for miata engines to idle stably at this actual rpm, because it definitely wasn't complaining (i increased the idle after i saw this):
Attached Thumbnails
funky tach readings-img_0144.jpg  

Last edited by frostyllama; 08-31-2010 at 10:44 PM.
frostyllama is offline   Reply With Quote
Old 08-31-2010, 11:14 PM   #2
Newb
iTrader: (1)
 
Join Date: Mar 2010
Posts: 40
Total Cats: -4
Default

what computer are you using? is the battery and coil good?
GVwannabe is offline   Reply With Quote
Old 08-31-2010, 11:44 PM   #3
Junior Member
Thread Starter
iTrader: (3)
 
frostyllama's Avatar
 
Join Date: Feb 2008
Location: Pollock Pines, CA
Posts: 281
Total Cats: -2
Default

computer? i have a stock ecu, i haven't checked the battery or the coil, those are probably good places to start. i plan on upgrading to cops, so that should eliminate the problem if it is coil related. i'll check the battery when i get i chance, but come to think of it those two things make a lot more sense.
frostyllama is offline   Reply With Quote
Old 09-01-2010, 04:08 AM   #4
Elite Member
iTrader: (4)
 
MartinezA92's Avatar
 
Join Date: Aug 2009
Location: Mountain View, CA
Posts: 1,702
Total Cats: 28
Default


Grounds grounds grounds.
This is a really common problem.
MartinezA92 is offline   Reply With Quote
Old 09-01-2010, 04:38 AM   #5
Senior Member
iTrader: (2)
 
Join Date: Nov 2007
Location: Saint Paul, MN
Posts: 1,295
Total Cats: 22
Default

Check the ground behind the head under the heater core, and on front of the block by the throttle body.
Der_Idiot is offline   Reply With Quote
Old 09-01-2010, 07:05 PM   #6
Junior Member
Thread Starter
iTrader: (3)
 
frostyllama's Avatar
 
Join Date: Feb 2008
Location: Pollock Pines, CA
Posts: 281
Total Cats: -2
Default

Quote:
Originally Posted by Der_Idiot View Post
Check the ground behind the head under the heater core, and on front of the block by the throttle body.
this makes even more sense. i'll check it out when i get a chance.
frostyllama is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 58 12-13-2017 10:04 PM
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
Low oil pressure after 1.8 swap and new turbo setup JesseTheNoob DIY Turbo Discussion 15 09-30-2015 03:44 PM
Are my coils failing? viriiguy General Miata Chat 5 09-28-2015 08:39 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:54 AM.