Automotive Forums .com - the leading automotive community online! Automotive Forums .com - the leading automotive community online!
Automotive Forums .com - the leading automotive community online! 
-
Latest | 0 Rplys
Go Back   Automotive Forums .com Car Chat > Volvo > 780
Reply Show Printable Version Show Printable Version | Email this Page Email this Page | Subscription Subscribe to this Thread
 
Thread Tools Search this Thread
Old 04-06-2006, 06:30 PM   #1
nightsurfride
AF Newbie
 
Join Date: Apr 2006
Location: Mountain View, California
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
88 Volvo 760 Turbo Twitching Tach.

I am working on an 88 Volvo 760 Turbo 2.3L. When the vehicle is not warmed up, the tachometer needle twitches upward as much as 300RPM and then quickly back to the correct reading. The engine has steady RPM. I checked the CKP sensor wire at the Dist. and found a nice, clean, even square wave pattern that changed proportionately with engine RPM. The clean waveform is also seen on the input signal wire to the power stage. I checked both the signal wire from the power stage and signal wire to the inst. cluster which showed a waveform much similar to that of an inj. pulse, but with a 12 volt steady section in between the on/off time voltage spikes. This steady voltage section is the same as the clean waveform signal steady voltage of 5 volts as seen straight from the CKP and into the power stage. I am not sure if this stepped up wave form seen coming from the power stage and also into the inst. cluster is a good pattern, but it seems to stay the same even when the vehicle warms up and the twitching tach. stops twitching, so I am assuming that it is not the problem. The tachometer display/head has been replaced in the past for unrelated issues, but the twitching tach. problem was there before and after the replacement of it, so it is fairly safe to rule that out as well. Any ideas on what I should check next, or what might be causing this problem? Thanks for your time.
nightsurfride is offline   Reply With Quote
 
Reply

POST REPLY TO THIS THREAD


Bookmarks
Go Back   Automotive Forums .com Car Chat > Volvo > 780

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -5. The time now is 01:48 AM.

Community Participation Guidelines | How to use your User Control Panel

Powered by: vBulletin | Copyright Jelsoft Enterprises Ltd.
 
 
no new posts