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Author Topic: '85 GF idles/ runs rough... reasons/ fixes?  (Read 1026 times)

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granfurious

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'85 GF idles/ runs rough... reasons/ fixes?
« on: January 02, 2011, 14:38:17 »

I have an '85 Gran Fury Salon that I bought off a farmer down the road about a month ago.  I just couldn't resist it for $800.  It has the original 2bbl 318 in it with 82k miles. 

The car starts up fine, but it sounds like it's missing when it idles and runs.  It doesn't seem to make much difference whether it's cold, warmed up, running, under acceleration, etc.  When it's idling it kind of backfires a little.  I've attached a pic from under the hood.  I was wondering if anyone knew what might cause this to happen on this car.  As you can see in the pic, the hose is missing that returns warm air up to carb.  Does that have something to do with it?  Could it be the Electronic Fuel Control System on it?  If that was bad, would it make the car miss?  Does anyone know how much it costs to replace one of those, and are they available at an Auto Zone or other auto parts store?

Thanks.  I appreciate any advice anyone can give me.  I was originally going to drive this car this winter just as a beater, but it doesn't have much rust on the body and it's kind of fun to ride around in, so rather than totally destroy it with road salt I'd like to try to fix it up this winter and then drive it a little come summer.

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granfurious

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #1 on: January 02, 2011, 14:39:42 »

by the way, in case anyone's interested, this is a pic of the car.  It wouldn't let me attach both pics to my first message.

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Mike

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #2 on: January 02, 2011, 16:35:06 »

The computer could cause it but so could carb problems, ignition problems, needing a tune up and a lot of other things. The only way to fix it or to even know what is causing it is to start with the simple things and go from there.
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270SE

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #3 on: January 02, 2011, 16:58:12 »

Computer could be an issue, timing chain may be a problem, that shouldn't have anything to do with it but it's called a preheater hose and isn't very expensive.

What's "kind of backfires"? It fires through the exhaust, or up the carb, or it doesn't.
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lsm360

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #4 on: January 02, 2011, 17:04:52 »

Nice looking M, and I dig that older Dodge truck next to it 
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DobaMark

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #5 on: January 02, 2011, 17:36:57 »

Do a tune up.  The spark plugs will tell you a lot.  My bet is a combination of fouled plugs, old wires and a bad carb.  Make sure to change the small things also like cap, rotor and PCV valve.  The air tube you point out is only active when the car is cold and won't affect the engine when warm.  If the car's been setting, and it may well have with the lower mileage, the gas may have turned to varnish both in the tank and in the carb.  Chances that it is the computer are small.  I've never replaced a bad computer and I've been driving cars with this style ignition since they were new (1981 actually).  Given the age, the timing chain could be an issue but get the basics sorted out first.
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granfurious

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #6 on: January 03, 2011, 09:44:19 »

Thanks.  I'll try the tune-up.  The plugs, wires and cap look pretty new, but I'll pull them and check them anyway.  The roads are clear here right now so I drove it around a little yesterday and did notice that as it got up to temperature the roughness gets better, even though it doesn't totally go away.

The car makes a popping noise through the exhaust when it's idling.  It's not backfiring up through the carburetor or anything.

Thanks for the compliment on my truck.  It's an '88 D-150 with 265K miles on the original 318 and it runs like a charm, which is why I didn't hesitate to buy this car knowing the engines were similar.  I've never really had to work on the truck's engine though, she just starts up and runs so I don't know a ton about working on 318's.
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270SE

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Re: '85 GF idles/ runs rough... reasons/ fixes?
« Reply #7 on: January 03, 2011, 11:33:19 »

Does the choke close at all?
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