rough idle?
Senior User
Joined: Nov 2002
Posts: 163
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From: chicago
rough idle?
[updated:LAST EDITED ON 09-Dec-02 AT 09:37 PM (EST)]my search icon does not come up so that is why i am posting this ? I have a 79 250 4x4 with all original 400. it idles a little rough but otherwise performs great. no hesitation, surging, missing, or pinging. i replaced duraspark module with a factory one. new plugs and wires. no apparent vacuum leaks. it smells rich idling. what could it be? it idles rough enough to vibrate the mirrors a litlle and that is what annoys me. the guy i bought the truck from did not do much highway driving. could it be excessive carbon buildup on the backs of the valves? oh, what is the size of the factory side mount tank on my truck?:-X12
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
rough idle?
Could be carbon build up. I would remove the EGR valve and clean or replace it. They tend to get carbon build up and fail to close all of the way which can give you a rough idle. Also try adjusting the mixture screws on the front of the carb. Turn them in until the idle starts to drop then back them back out until you get the fastest, smoothest idle. If you have a vacuum gauge, then adjust them until you get the highest vacuum.
I would check the EGR valve first, then adjust the carb.
Jimmy
I would check the EGR valve first, then adjust the carb.
Jimmy
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
rough idle?
Rusty,
Do a compression check. Start at the beginning and you'll finish at the end. I know that doesn't make too much sense but if you don't start at the bottom, you may skip something and never see what the problem is after you spend alot of money. If your valves are shot nothing you do will make a difference. Check your compression.
KingFisher
Do a compression check. Start at the beginning and you'll finish at the end. I know that doesn't make too much sense but if you don't start at the bottom, you may skip something and never see what the problem is after you spend alot of money. If your valves are shot nothing you do will make a difference. Check your compression.
KingFisher
