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Mis at idle

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5 years 3 days ago #28878 by amd.auto
Mis at idle was created by amd.auto
2004 GMC Sonoma 4.3 4wd. Donr lower intake and replaced distributor. Replaced distributor due to no spark. and intake due to leak. Starts fine but white smoke out exhaust clears up then comes back but constant miss. Haven't changed the plugs yes which are bad for customer but any ideas. I can get any info needed. And I use a mac mdt10 scanner for all information.

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5 years 3 days ago - 5 years 3 days ago #28882 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic Mis at idle
Any sign of lost coolant ? Single cylinder misfire at cold start up can be a head gasket or manifold gasket leak.
My next move would be some kind of compression test, but I suspect it may not show a bad cylinder.
A valve guide oil seal problem can cause grey smoke when the throttle is opened but clears.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Last edit: 5 years 3 days ago by Andy.MacFadyen.

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5 years 3 days ago #28891 by Tyler
Replied by Tyler on topic Mis at idle
The white smoke definitely suggests coolant, but could also be fuel from a stuck open injector or fuel leak beneath the upper intake.

Have a look at any codes, fuel trims at idle and 2500 RPM, and which cylinders show miss counts. Also have a whiff of the smoke to see if it's fuel, coolant or something else. ;)

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