Slant Six Forum :: Rough Idle Intermittant

I have a 1986 Dodge D150 pickup, 225 cu in six, auto trans. New intake and exhaust manifold, carburetor, plugs, points, distributor cap and rotor, fuel pump and fuel filter, PCV valve. I checked the float setting in the carburetor and it was fine. PCV valve rattles continuously. Engine starts and idles beautifully. It accelerates smoothly. Problem is after normal acceleration from a traffic light, at the next light the idle is awful, the engines shakes and bucks. If I stay parked for a few minutes after the rough idle, it smooths out again. If I drive slowly from point to point the idle is fine. Sounds like a low fuel level in the carburetor to me but I checked that. I checked for vaccum leaks and found one small one on cylinder #1 intake manifol. I tighted it down and it was reduced. Looks to me that it would not ever idle well if the vaccum leak was the problem. Any ideas?

Author:	jkotis [ Wed Jan 12, 2011 11:00 pm ]
Post subject:	Rough Idle Intermittant
I have a 1986 Dodge D150 pickup, 225 cu in six, auto trans. New intake and exhaust manifold, carburetor, plugs, points, distributor cap and rotor, fuel pump and fuel filter, PCV valve. I checked the float setting in the carburetor and it was fine. PCV valve rattles continuously. Engine starts and idles beautifully. It accelerates smoothly. Problem is after normal acceleration from a traffic light, at the next light the idle is awful, the engines shakes and bucks. If I stay parked for a few minutes after the rough idle, it smooths out again. If I drive slowly from point to point the idle is fine. Sounds like a low fuel level in the carburetor to me but I checked that. I checked for vaccum leaks and found one small one on cylinder #1 intake manifol. I tighted it down and it was reduced. Looks to me that it would not ever idle well if the vaccum leak was the problem. Any ideas?

Author:	63Dart [ Thu Jan 13, 2011 2:43 am ]
Post subject:	Re: Rough Idle Intermittant
I've had this before. It was the throttle linkage! It was kind of binding under normal driving - so under normal driving, it would stay "bound" - then would loosen up and fall back down to a slower idle after I "got on it." Quote: I have a 1986 Dodge D150 pickup, 225 cu in six, auto trans. New intake and exhaust manifold, carburetor, plugs, points, distributor cap and rotor, fuel pump and fuel filter, PCV valve. I checked the float setting in the carburetor and it was fine. PCV valve rattles continuously. Engine starts and idles beautifully. It accelerates smoothly. Problem is after normal acceleration from a traffic light, at the next light the idle is awful, the engines shakes and bucks. If I stay parked for a few minutes after the rough idle, it smooths out again. If I drive slowly from point to point the idle is fine. Sounds like a low fuel level in the carburetor to me but I checked that. I checked for vaccum leaks and found one small one on cylinder #1 intake manifol. I tighted it down and it was reduced. Looks to me that it would not ever idle well if the vaccum leak was the problem. Any ideas?

Author:	olafla [ Thu Jan 13, 2011 7:31 am ]
Post subject:
Me too! I discovered it at the time because I was totally empty of all ideas about what could be wrong, so I just stood there and stared at the carb, and suddenly something in the linkage moved all by itself! When that is said, seeing to that things move freely is one thing, it is very easy to over-lubricate; oil and grease accumulates dirt and dust and may actually be the cause for binding joints. Olaf.

Author:	jkotis [ Sat Jan 15, 2011 7:14 am ]
Post subject:
Yes, you guys are correct. The idle was set when the throttle linkage was not all the way closed. The movement is very small, maybe 1/8" at the very most. I have ordered new throttle return springs and will check the throttle linkage for binding. Thanks for the suggestions.

Author:	wjajr [ Sat Jan 15, 2011 1:36 pm ]
Post subject:
Sometimes one will find egged out holes, and worn in grooves where a rod connects to its mate. After awhile, these worn spots conspire to impede free movement at these joints or connections. To relive binding, dress the spots where worn with a fine file, smoothing imperfections out so that no binding takes place. This may take several disassemblies, filing, and reassembling before the linkage moves freely. Remove a little metal as possible. Be sure to examine all linkage from gas pedal to carburetor for problems, and obstructions such as carpet & padding. Remove any rust, and lubricate any hinges & pivot points housed within the cockpit, making sure that these items move effortlessly. Once all the binding spots are removed, the linkage will move freely not requiring a heavier throttle return spring.

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Author:	63Dart [ Mon Jan 17, 2011 9:46 am ]
Post subject:
Awesome! I'm not a great mechanic - but I am usually pretty good at diagnosing problems (which I then let other people fix). . . Quote: Yes, you guys are correct. The idle was set when the throttle linkage was not all the way closed. The movement is very small, maybe 1/8" at the very most. I have ordered new throttle return springs and will check the throttle linkage for binding. Thanks for the suggestions.

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