Rough running 302.....
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Elder User
Joined: Nov 2001
Posts: 892
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From: Duluth, MN
Rough running 302.....
If it ain't broke.....change stuff till it is!
Ok..i own an 86' f-150 4x4 with the 302 efi. when i start it up, it runs fine, but after it warms up it starts to run rough with a varied rpm reading. the rpm's will vary from like 400 to 700. they go up and down randomly. is this a clogged cat.? or a vacuum leak of some sort? what can i look for and where is it on the engine...thanx.
I just changed the plugs. Also, if i step on it after driving a while(while in park and rev. to about 300 rpm's) black carbon smoke comes out the pipes. could this be a fuel filter too? any help would be appreciated....
Ok..i own an 86' f-150 4x4 with the 302 efi. when i start it up, it runs fine, but after it warms up it starts to run rough with a varied rpm reading. the rpm's will vary from like 400 to 700. they go up and down randomly. is this a clogged cat.? or a vacuum leak of some sort? what can i look for and where is it on the engine...thanx.
I just changed the plugs. Also, if i step on it after driving a while(while in park and rev. to about 300 rpm's) black carbon smoke comes out the pipes. could this be a fuel filter too? any help would be appreciated....
Thread Starter
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Elder User
Joined: Nov 2001
Posts: 892
Likes: 1
From: Duluth, MN
Rough running 302.....
If it ain't broke.....change stuff till it is!
If i was to purchase and replace the fuel filter and 02 sensor, would this help in the rough idle too?
Does the 86' f-150 4x4 have 1 or 2 filters?
If i was to purchase and replace the fuel filter and 02 sensor, would this help in the rough idle too?
Does the 86' f-150 4x4 have 1 or 2 filters?
New User
Joined: Feb 2002
Posts: 14
Likes: 0
From: Vancouver Washington
Rough running 302.....
Bring the engine up to temp first. Try the IAB valve on the intake of the Throttle body, it is sticking. Buy a replacement gasket (felt) and remove the IAB body from the housing, spray carb cleaner in it and let it sit. Also spray into the throttle body to remove any visible dirt. Let it dry of any excess in there and reinstall. The engine will not start up right away, but it will. Sure worked for me.
John (JC)
1977 F150 302
1987 Nustang GT (244K and still running new)
John (JC)
1977 F150 302
1987 Nustang GT (244K and still running new)
Thread Starter
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Elder User
Joined: Nov 2001
Posts: 892
Likes: 1
From: Duluth, MN
Rough running 302.....
If it ain't broke.....change stuff till it is!
How do u change the rich mixture? I took the TB off today and sprayed it out along with the IAB, and it runs a bit better. btu it still sounds like the engine is shuddering when i go to slow down at stop signs. it feels fine accelorating, but goin into stop signs is when it sounds and feels terrible. is this a plugged cat? if so, whats the easiest way to go about knocking the crap out of the inside? i don't want to replace it , because we don't have strict emission laws, so if i can just get the stuff out and leave the shell, that would be great. also...could an exhaust manifold leak cause this surging?
How do u change the rich mixture? I took the TB off today and sprayed it out along with the IAB, and it runs a bit better. btu it still sounds like the engine is shuddering when i go to slow down at stop signs. it feels fine accelorating, but goin into stop signs is when it sounds and feels terrible. is this a plugged cat? if so, whats the easiest way to go about knocking the crap out of the inside? i don't want to replace it , because we don't have strict emission laws, so if i can just get the stuff out and leave the shell, that would be great. also...could an exhaust manifold leak cause this surging?
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