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Rough Idle 1990 5.7

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Old 07-03-2009, 09:12 PM
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Default Rough Idle 1990 5.7

I have a full size 90 with the 5.7. I have had problems with rough idle while in gear. I had a friend check the timing and it was set at 6 so he put it back to 0. That worked for about two week till I replaced the battery. I checked the idle and in park its about 550. I checked for any vac leaks and found none, any ideas????
 
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Old 07-03-2009, 10:38 PM
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Have you cleaned or replaced the EGR valve? When was the last tune-up? A sticking pintle valve in the EGR valve or worn spark plugs/wires/cap/rotor could cause that.

Josh Hucks
 
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Old 07-03-2009, 10:46 PM
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Originally Posted by jhucks03 View Post
Have you cleaned or replaced the EGR valve? When was the last tune-up? A sticking pintle valve in the EGR valve or worn spark plugs/wires/cap/rotor could cause that.

Josh Hucks
EGR has not been cleaned or replaced. Last tune up was july 08 plugs/wires/cap/rotor/fuel filter. EGR looks to be factory org. itsgot 104k on the the org. motor
 
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Old 07-04-2009, 08:50 AM
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Have you checked or replaced the throttle body base gasket? These are known to leak causing a vacuum leak that is very hard to find.

How does the fuel spray out of the injectors look?
 
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Old 07-04-2009, 04:00 PM
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Clean the throttle body and Idle Air Control. You are running AC Delco spark plugs right? I would also re-check the cap, rotor and wires... take a look at the plugs for any weird color or signs of fouling.
 
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Old 07-04-2009, 05:35 PM
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I am running ac deco plugs and injector spray looks good. Will look over the other things noted. Thanks for the help. Will keep post up to date.
 
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Old 07-05-2009, 10:16 PM
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I found 1 of my plug wires has been melted a little. It doesnt look to bad but could this be a problem? It now has a bad vibration at hwy speeds. I dont dare do above 65mph
 
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Old 07-05-2009, 10:27 PM
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If you suspect the wires being a problem, mist them down at night with the engine running with as little ambient light as possible. If you see arching from the wires, they need to be replaced.
 
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Old 07-05-2009, 10:40 PM
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Originally Posted by swartlkk View Post
If you suspect the wires being a problem, mist them down at night with the engine running with as little ambient light as possible. If you see arching from the wires, they need to be replaced.
Thanks for the tip, going to try it tonight
 
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Old 07-10-2009, 02:00 PM
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Problems solved


Wires were bad and U Joint was bad

Thanks for the help
 

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