Can't get a steady idle...
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
Can't get a steady idle...
I'm having an issue on my '84 with 302/ 2bbl; I can't seem to achieve a steady idle. When I set the idle to where it should be which I seem to remember is around 750 (manual trans), it searches between 700 and 1,000. I've attempted to adjust the carb with a vacuum gauge to get highest possible reading with leanest setting which is now fluctuating between 17"-21". I've reset the timing, still to no avail. It seems to be running very rich even after leaning it out. I just set the thing for 1,000 RPM because I'm afraid it's going to stall at a red light. I've also disconnected the idle control motor with no change. Is there anything to look at first before I start ripping things apart to diagnose the timing set/cam/lifters, etc? My vacuum lines are all new so I don't suspect a vacuum leak.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
I extracted your post from reamer's thread and created your own with it; one problem per thread works well here and hijacking is discouraged.
Please feel free to edit & set the Title to whatever you want....
-ct
Please feel free to edit & set the Title to whatever you want....
-ct
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Where are you getting your vacuum for the advance? I'd bet you are using manifold vacuum. If so, pull the vacuum line and plug it - do you still have problems? If not, find ported vacuum where there's no vacuum at idle, and use that.
Super Moderator
Joined: Apr 2004
Posts: 34,499
Likes: 2,811
A wandering idle is one symptom of a sloppy timing chain. Pull your distributor cap and rotate the engine until the rotor moves. Then reverse rotation and note how much crank rotation you have before the rotor moves. That is how much your cam and ignition timing wanders at idle.
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
But to get to the end of your statement, a ported vacuum source should have 0" of vacuum at idle? This port I am using has some vacuum at idle, but not at 0".
Trending Topics
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
Carb is still original but was completely rebuilt last year- used new gaskets and bolts are still tight. I suppose that's not to say the gaskets are defective or the carb base is warped...
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
A wandering idle is one symptom of a sloppy timing chain. Pull your distributor cap and rotate the engine until the rotor moves. Then reverse rotation and note how much crank rotation you have before the rotor moves. That is how much your cam and ignition timing wanders at idle.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
If you have the throttle plates open very much you will have some vacuum at idle. And since the advance can start coming in at about 10", that's too much.
What causes the throttle plates to be open too much is a poor air/fuel mix and/or late ignition timing.
What causes the throttle plates to be open too much is a poor air/fuel mix and/or late ignition timing.
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
Pardon my ignorance but how does the ignition timing affect the position of the throttle plates? I thought those could only be controlled by either the accelerator pedal or by turning the idle adjustment screw.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Well, yes and no. Late engine timing makes the engine idle slowly so you have to open the throttle more to get the RPM up where you want it. And a rich air/fuel mix makes it run slowly as well. So lean out the mix and turn up the timing. That'll let you close the throttle plates.
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
Well, yes and no. Late engine timing makes the engine idle slowly so you have to open the throttle more to get the RPM up where you want it. And a rich air/fuel mix makes it run slowly as well. So lean out the mix and turn up the timing. That'll let you close the throttle plates.
Still trying to figure out why it's running so rich still, I've got it leaned out as much as I can, any leaner, the engine wants to stall.
Thread Starter
|
Senior User
Joined: Dec 2014
Posts: 233
Likes: 0
From: Buffalo
I'd have to think they quit using nylon long ago, but who knows. Until I open it up I won't know for sure. I remember taking apart the 460 on my '69 Mark III and saw nylon gears and I was amazed that they were still in perfect condition but still wondered how they could ever be so (and I hate to use this word) DUMB and think that would ever last.