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1985 Ford idle problem


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Dnake1
Novice

Jun 16, 2009, 11:52 AM

Post #1 of 16 (8884 views)
1985 Ford idle problem Sign In

F250,460 cu in engine,Holly4180C carb.
I have owned this vechicle for 8 years. Normally when started cold it goes to a very high idol until warms up then goes to normal.Suddenly now when started cold, doesn't go to fast idol but the auto choke seems to open properly.Runs well at higher rpm but doesn't idol very good and carb is loading up. All the emission hoses seem to be okay.Before I start replacing the carb, could the emission stuff be causing the problem? Nothing mechanical has been done recently ha been done to the vechicle.
Thank you,
Tom


Loren Champlain Sr
Veteran / Moderator
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Jun 16, 2009, 1:34 PM

Post #2 of 16 (8877 views)
Re: 1985 Ford idle problem Sign In

Dnake; The cold fast idle speed should be around 1700rpm. With the engine cold, prior to starting, the choke should be closed. (may have to tap the throttle to allow it to close). You should be able to feel a bit of resistance if you push the choke butterfly open with your finger. Once the engine starts, the choke should open about 1/8" initially. If it doesn't, it will cause a flooding condition. The vacuum operated choke pull-off is responsible for this. Some, are internal in the carb, others an external diaghragm. Also, make sure that you are getting 12V to the choke thermostat with the engine running. The choke thermostat (electrical) heats the choke and causes it to open as the engine warms.
The choke thermostats do go bad. And, the linkage can get gummy and sticky. A can of carb cleaner will clean up the fast idle linkage if that's the problem. If the engine is still 'loading up' after the choke has opened and the engine is warm, then that's another story. Let us know.
Loren
SW Washington


Dnake1
Novice

Jun 16, 2009, 3:39 PM

Post #3 of 16 (8875 views)
Re: 1985 Ford idle problem Sign In

Thank you for your prompt reply.I'll try the cleaner.The choke is opening fully and still getting black smoke and rough idle.This suggests Needle/float problem but shouldn't have any affect on decreased rpm on cold start up.


Loren Champlain Sr
Veteran / Moderator
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Jun 17, 2009, 12:04 PM

Post #4 of 16 (8868 views)
Re: 1985 Ford idle problem Sign In

Depending on which Holley you have, most had externally adjusted floats.
Loren
SW Washington


Guest
Anonymous Poster

Jun 17, 2009, 1:05 PM

Post #5 of 16 (8864 views)
Re: 1985 Ford idle problem Sign In

Thank you,
The carb is apparently a .
4180C made for motocraft by Holle.The no. on the outside tag:Motocraft E3TERD,B4L13
The no. the carb body: E3TE-9510-RD,List 50003-1, 3184.
I'll try tofind a book on the carb.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jun 19, 2009, 1:04 PM

Post #6 of 16 (8854 views)
Re: 1985 Ford idle problem Sign In

Just a note: The alcohol (methanol) can raise hell with materials used in older vehicles. Carb kit for eth-alch may be needed,

T



Dnake1
Novice

Jul 23, 2009, 7:40 AM

Post #7 of 16 (8796 views)
Re: 1985 Ford idle problem Sign In

Update. Replaced the distributor and this solved the idle problem. Now the problem is it will run for a couple of miles and slows down and start backfiring through the carburetor and then a large backfire from the exhaust. Timing is set at 8 degrees BTDC per vechicle specs. Used the old cap and wires.They look very good with no visible signs of wear or leakage when run in a dark room.
Can the carburetor still be the problem or could the cap or rotor be a problem even though no visible signs of damage.
Thanks again.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 23, 2009, 9:35 AM

Post #8 of 16 (8789 views)
Re: 1985 Ford idle problem Sign In

You might want to replace that distributor again. It sounds like something in the ignition is being effected buy heat and breaking down. If you didn't have the problem before, it's likely something in the distributor.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 23, 2009, 9:42 AM

Post #9 of 16 (8786 views)
Re: 1985 Ford idle problem Sign In

There are still more possibilities. Ign secondaries should NOT react if wet for any reason. You could mist cap and wires while fairly dark and they could show a flaw when sprayed - arching.

If high miles or not the timing chain if known original could have used a nylon cam gear. Those don't like high miles nor age unfortunately. You can turn crank bold to TDC one way and watch how many degrees going opposite way for how many degrees it can go without turning the dist rotor. 5-6 is plenty or could be the issue.

Also carb's choke could be the issue. It's a tad odd that you get both exhaust and intake backfires just with a choke issue on carb though. Watch it's operation that it's proper would help peg down the issue,

T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 23, 2009, 10:12 AM

Post #10 of 16 (8781 views)
Re: 1985 Ford idle problem Sign In

The large backfire that you describe in indicative of primary ignition cutting out and the backfire is the result of fuel accumulation with no spark that ends with a single spark that ignites the accumulated fuel. I think for sure your problem is ignition and most likely the primary side, not the cap and rotor.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Dnake1
Novice

Jul 25, 2009, 2:16 AM

Post #11 of 16 (8763 views)
Re: 1985 Ford idle problem Sign In

Thanks guys,
Put the old distributor on. Set timing and it advances about 5 degrees when you rev up the engine.The backfiring is gone but the driving down the road is still a problem.It idles okay and will run up to a mile or better then start to slow down.It acts as though you are turning the switch on and off. Filled the tank with fresh gas and changed the fuel filter(which looks good) and no improvement. If you drive about 35 to 40 mph it seem normal, but a soon as you speed up to 55-60 mph it will slow down and start to balk. Found a shop that still works on old vechicles but its about 60 miles away. Would prefer to drive it there rather than haul it(its a guy thing).
Have a great weekend.Appreciate any ideas when you have time.


Dnake1
Novice

Jul 29, 2009, 4:34 AM

Post #12 of 16 (8728 views)
Re: 1985 Ford idle problem Sign In

Tom Greenleaf,
I did the test for timing chain slack,The movments are very jerky(spark plugs still in).The rotor moves at about the 6-8 degrees area.Would this be enough to cause the timing chain to jump a cog.The reason I ask is,when I retard the timing about 5-6 degrees the backfiring goes away and It will run at 65mph easily.At 70 mph it starts to balk a little but no backfire.Old distributor still instaled with new vacumn advance. Run crappy at low rpm and doesn't idle very good.
Thanks again.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 29, 2009, 6:02 AM

Post #13 of 16 (8720 views)
Re: 1985 Ford idle problem Sign In

IDK 100% if 460s used nylon gear. If you know it is original and watch 8 degrees of change it's done with. The nylon wouldn't hold up from just time and heat. Once done I've never done another on same vehicle no matter how many more miles they got after getting first ones out. Planned obsolescence at it's best - not just Ford.

Now long retired - I used to do timing chains for this and much older if they needed a water pump as you were mostly there for the chain. They plain run better with a new all metal one!

I just by chance don't recall how hard a chain is on a 460 or if I ever did one on the specific engine. Don't ask why but for some mystical reason the chains when bad enough can jump off time and back on time for years and folks put up with it. Me for one did just that on a car of my own that once in a blue moon would backfire then be fine for months. When I had to walk and finally did what I suspected on that old Olds 98 - 455v the original chain came off without removing the gears first! I was shocked because I knew that car from new with no missed oil changes or overheats in it's history.

These are 1/4 million mile engines but most have had a chain TMK in their history. I've owned one at over 200k but it was done and ran as new @ 30 years old! Laugh - the pre smog 460s would pass anything but a gas station!

If you love this thing I'd put that on the list and no harm done just a lot of time and isn't that expensive. It makes it easier if you take the radiator out to do them and use air tools if available to you.

You might see with the timing light at assorted revs it may stay steady on the marks or jump around right in front of you if you have a good timing light.

Your call of course if you know the history,

T



Guest
Anonymous Poster

Jul 29, 2009, 7:02 AM

Post #14 of 16 (8714 views)
Re: 1985 Ford idle problem Sign In

Thanks Tom,
Don't know the history. Bought it about 8 yrs ago with 75,000 miles.About to turn over to 80,000 miles.Another guestion,I'm using my old timing light from the 60's that uses an adpter to hook to the plug wire. Also because of the rough idle having trouble keeping a stable rpm while testing.Would either have a material affect on setting the timing.When I turn it to 8 btdc it lines up really close to no. 1 plug wire.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 29, 2009, 8:11 AM

Post #15 of 16 (8705 views)
Re: 1985 Ford idle problem Sign In

If not getting interference and do get a regular flash the light should be fine. I have now and antique "advance" Snap-On so you set it to the desired timing and just look for TDC and is inductive pick up.

That's not a lot of miles but like I said the nylon isn't age or heat friendly. I have a clean #2 88 Town Car 302 in reality and want to keep it forever so it's getting a timing chain just because of the age and about 90k totally cared for car.

When you said retarding the timing eliminated the backfires makes me think the chain is possible and if 8 degrees off was seen with a static test then I just have to wonder. 85 was tough to have a carb too as emission limits came they hung on too long fussing with carbs (many car makers) before giving in almost completely to FI a couple years later.

This could be dual issues also. Hard to say without some testing and making sure one thing is definitely fine and go on to the next when and if you know it is. Keep at it,

T



Loren Champlain Sr
Veteran / Moderator
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Jul 29, 2009, 2:20 PM

Post #16 of 16 (8695 views)
Re: 1985 Ford idle problem Sign In

Dnake; 8 degrees is too much. And, 5 degrees advance is not anywhere near enough. Anything above 6 degrees of timing chain slop is too much. The centrifugal advance should be in the 20 degree neighborhood. With the vacuum advance connected, you should be seeing total advance in excess of 30 degrees.
Loren
SW Washington






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