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Discussion Starter · #1 ·
Got a 68 mustang with a 289, which is idling really lumpy, it started to play up about a week ago and the problems has been fairly intermittent since then, sometimes running perfectly and sometimes hardly idling at all.

If you touch the throttle it seems to rev fine and smooth out, and i can't feel any problem when driving, except on really light throttle when it hunts a bit.

I've checked points, timing etc, fitted a new fuel line with a filter in case it was dragging crap up. Looking at it today I started pulling plug wires off to try and isolate a cylinder, and pulling off 4 of the 8 plug leads (every other one in the firing order) made no difference to the idle at all, pull any one of the other 4 and the engine would stall.

Any ideas?
 

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Discussion Starter · #3 ·
I've had a spray round, can't find any leaks. I'll try the plugs.

I'm starting to wonder if I've got a duff carb (it's the stock 2 barrel)

Jon
 

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What's throwing me is the fact of ''pulling four leads is not affecting the idle''. Other than that I would say possibly dirt in the carb. Check the needle valve and clean and then if that does not help maybe do a basic carb strip/blowout/rebuild.
 

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i would guess dirt in the carb idle circut first, then because its the stock 2 bbl carb thats got lots of miles check for wear on the throttle spindle, when worn lets extra air in and upsets the idle
 

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Do the 4 leads that cause the stall correspond with 4 runners from the same side of the carb? Or is it not set up like that.
 

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Discussion Starter · #7 ·
The bad cylinders are 2 on each bank, every other one in the firing order.

I'm guessing the manifold does branch off 4 ways from each barrel?

I'll pull the carb off and have a poke around, and give the carb a blow out while I'm there.
 

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i wouldnt go that far mate just clean the carb out! :D

jim
 

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The bad cylinders are 2 on each bank, every other one in the firing order.

I'm guessing the manifold does branch off 4 ways from each barrel?

I'll pull the carb off and have a poke around, and give the carb a blow out while I'm there.
That's how the 4 barrel dual plane works. You should be able to tell the layout of the runners without removing the carb.
 

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No need to remove carb to fix problem, as it sounds like one side of the idle circuit is gummed up. To find out which side just spray a little carb cleaner into the throat of the carb with the engine running, one side at a time. The extra fuel in the good side will cause the engine to stumble, but in the bad side the engine will smooth right out. To clean them [might as well do both] simply shut off the engine, unscrew the idle mixture screws, place a rag over the top of the carb to catch the resulting spray and give a healthy squirt of carb cleaner into each idle hole. [Berryman is by far the best if it is available over there.] Follow this up with a good blast of compressed air. Reinstall the screws, all the way in and then back out one and a half turns.The car should now start and idle fine. Fine tune the idle to suit.
 

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Discussion Starter · #13 ·
Just followed the advice above and it seems to have done the trick, at least for now.

Thanks to all for your help

Cheers
 
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