289 4v wont idle more than a couple minutes - MustangForums.com



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Old 11-13-2016, 02:46 PM   #1
zeddy
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Default 289 4v wont idle more than a couple minutes

I have a 65 mustang gt with a 289 and a 4100. It has always smelled awfully rich at idle so yesterday I went to adjust the mixture and somehow I screwed up( I think I turned one side in and the other out) and I flooded it really. bad. I left it overnight and still couldn't start it today so I pulled the plugs cleaned them. I opened the butterfly and blew some air in there to dry out the fuel. I started with the base 1.5 turns out and got it started. I ended up somewhere around 2.5. The problem is that once totally warmed up it won't idle for more than a couple minutes or so. It idles fine for a good two or three minutes then stumbles once or twice then stalls. I have adjusted it up and down in 1/8 increments and it makes a slight difference(it takes longer to stall) but now I'm up around 3 turns out. The 289 is bored .0030 with a mild cam and ported heads. The 4100 has been rebuilt twice. It is a 1.12 venturi carb, I have no idea what size jets are in it. The points, wires, plugs fuel pump are all new. The car has a new fuel tank. I have put about 1000 miles on it since complete with no issues.
It has me completely frustrated. I have to quit for today but if anyone has suggestions on what to try it would be appreciated.
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Old 11-13-2016, 05:57 PM   #2
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There could be a blockage in a carb jet..you might want to pull the carb and clean it out..
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Old 11-23-2016, 10:51 PM   #3
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What about your curve Idle on your throttle linkage. Is it adjusted to keep it up to 7 or 800 RPM's after warm up? No mention of Choke or if you have one.
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Old 11-27-2016, 08:26 PM   #4
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It has an automatic choke and I had adjusted the idle to a little on the high side(about 900rpm) and it still dies.

I thought I had it close now I can`t even get it to start. it just floods.

What should I do to clean the jet? Back the needle right out and spray carb cleaner in it?
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Old 11-27-2016, 08:36 PM   #5
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It looks like an easy carb to work on.. I would remove it. Pull the top cover off and disassemble it. Pull the main jets and secondary jets clean all the passages, clean inlet needles and seats (it may not hurt to replace inlet needels and seats..if they are leaking it will cause flooding the carb is apart it might be a good time to do this.) clean out idle jets and passages. Take your time with it look carefully for debris caught in anything.
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Old 11-27-2016, 09:25 PM   #6
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I will do that. It's just a little frustrating as i have had the carb rebuilt twice in the last 500 miles.
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Old 11-27-2016, 09:45 PM   #7
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ahhh i over looked that part. was it the same issue that caused you to have the carb rebuilt or did this occur after the rebuild?
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Old 11-27-2016, 10:20 PM   #8
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I built a new motor, rebuilt the carb. On one of my first trips out I hit a bump and a float stuck. I took the carb back to the rebuild guy and he went through it again. Found nothing and I put it back on. I changed the fuel filter, flushed the lines. The tank sender and pump are new.
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Old 11-27-2016, 10:52 PM   #9
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so the carb had set for a long time and as far as we know has never worked right. Did this carb ever work right on say a previous motor? do you know what it came off of?

Its vitally important that at this point you know for sure that both inlet needles and their seats are new. If they are not new the rubber maybe hard and its unlikley they will seal reliably.

How much fuel pressure is your fuel pump making? If its over 7psi it will need to be regulated...You arent running like 9psi or something are you?
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Old 11-28-2016, 12:05 AM   #10
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This carb was on another 289 in my car. It ran fine. The block was the wrong year so I found a correct short block and transferred over the carb, manifold, and exhaust manifolds. The project took about 5 months so I had the carb rebuilt.

The pump is a NOS ford pump. I haven't checked it for pressure though. How would I rig a gauge?
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