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#1 |
Registered User
Join Date: Aug 2011
Location: Lakewood WA
Posts: 30
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we have 1989 Gmc s15 truck 112k miles
when I check timing instead showing at 8 degree it flickers between 6 to 10..sometimes 6 sometimes 8 or 10 etc. same thing with vacuum ..flickers between 14 to 17 etc. also when we start the truck it vibrates heavily and when stomp on gas pedal vibration stops...when we drive it does not vibrates..so am not sure...if this is due to engine mounts. I also think when engine is warm it does nor vibrates... changed spark plugs, checked wires for resistance, cleaned cap and rotor... what should be reason? and what's solution? |
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#2 |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: timing light does not shoot at steady 8
check for vacuum leak. IAC is attempting to bring things back to normal as well as ECM changing timing which accounts for fluctuating timing.
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
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#3 |
Registered User
Join Date: Jun 2011
Location: Richmond,Va
Posts: 2,934
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Re: timing light does not shoot at steady 8
I would agree with 68C15, if it fluctuates its internal like a miss. Remember, there is such thing as a lean miss which would be where he is pointing you. Simply enough, it is an internal problem and not a problem with mounts or something similar.
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Nick Carter 1967 C10 Short bed Fleetside Project Cheap Thrills! 2WD C10 Modern/Performance Alignments Easiest Alignment Ever! |
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#4 | |
Registered User
Join Date: Aug 2011
Location: Lakewood WA
Posts: 30
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![]() Quote:
also how do I check for IAC? if its working properly or something wrong there? |
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#5 | |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: timing light does not shoot at steady 8
Quote:
the IAC is like the sheriff in town. if he is arresting a bunch of drunk drivers he is not the problem, he's just doing his job.
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
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#6 | |
Registered User
Join Date: Aug 2011
Location: Lakewood WA
Posts: 30
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![]() Quote:
Thanks I found a vacuum leak and fixed the hose and it runs smooth now..truck or engine is not shacking any more...thanks for advice.. I did not understand what you meant for IAC though... |
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#7 |
Registered User
Join Date: Jun 2011
Location: Richmond,Va
Posts: 2,934
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Re: timing light does not shoot at steady 8
IAC= Idle Air Control
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Nick Carter 1967 C10 Short bed Fleetside Project Cheap Thrills! 2WD C10 Modern/Performance Alignments Easiest Alignment Ever! |
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#8 |
Registered User
Join Date: Oct 2009
Location: .
Posts: 2,185
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Re: timing light does not shoot at steady 8
when you check timing, are you unplugging the timing connector under the pass. side carpet?
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#9 |
Registered User
Join Date: Aug 2011
Location: Lakewood WA
Posts: 30
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#10 |
Registered User
Join Date: May 2002
Location: VA
Posts: 1,337
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Re: timing light does not shoot at steady 8
Yup, all computer controlled vehicles do.
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69 Chevy C10 88 Sierra 02 2500 Suburban And too many S10s to list! |
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#11 |
Registered User
Join Date: Aug 2011
Location: Lakewood WA
Posts: 30
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#12 |
Registered User
Join Date: Oct 2009
Location: .
Posts: 2,185
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Re: timing light does not shoot at steady 8
its up close to the fire wall and kick panel. a single wire connector, i cant remember what color the wire is
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#13 |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: timing light does not shoot at steady 8
tan with a black stripe
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Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card |
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engine mounts, rough idle, timing, vibration |
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