NEED HELP (long)...Bronco dies at idle and is running a little rough

[BamaBronco73]

??? First of all, I have a 73 w/ 302, stock(?) Motorcraft carb, stock points-style distributor.

I have noticed my Bronco running a little rough at idle lately. Seems to have been doing it about 50% of the time. Yesterday while driving, it just died at a red light when it dropped to idle from driving speed. I pressed the accelerator and it would crank back up. As long as I pressed the gas it would run (though a little rough) but would die when it went back to idle. Returning home, I could keep it running when I pushed the gas, but if I had to coast or come to a stop, I would have to shift it into neutral and rev it up. It cranks fine if the gas is depressed, but will not idle.
Any help is greatly appreciated. I believe it has to be either the carb or the distributor.... just not sure which way to lean to. May be leaning a little to the carb, as it just seems not to be getting gas at idle. It has new plug wires, plugs, fuel pump, fuel filter....so I can rule those out as they have been operating well for the last couple of months.
Thanks in advance.

 

[76Broncofromhell]

Sounds like a vacuum leak. What I do is spray carb cleaner in there while it's running. When it smoothes out (IE: the cleaner momentarily blocks the leak) you've found your leak. That or check all your vacuum hoses.

 

[GRIZZLY]

Idle set too low?

 

[Alex]

May be the distributor cap has a crack in it? Coulda lat in some moisture. I would change that and then check fuell filter and all the cheap obvious stuff.

 

[Gordys74]

Possibly one of the idle jets has something partially blocking it. Take out the needles (count the turns) and blow some air thru them then replace the needles. Might work, easy to do, and costs nuthin'.

 

[Skuzzlebutt]

Probably a vacuum leak like BroncoHell said. The leak could also be in the vac advance unit of the distributor, or a crack in the vac line. If you got an A/T there could be vacuum leaks down there too. Slight but unlikely chance the dist has come loose and needs to be retimed.

 

[ken75ranger]

I'd check the choke first when the vaccuum second.

 

[BamaBronco73]

Thanks guys for the ideas. Please keep them coming.

It is definitely not moisture in the distributor. My Bronco hasn't been off the road (or even out of the garage) around water.

I don't have a vacuum hose out of the vacuum advance on the distributor....never has had one.
A vacuum leak on the carb or a clogged idle valve may be the problem.

If it is the carb, can you recommend a replacement? I would rather replace than rebuild.

 

[BamaBronco73]

[quote author=Gordys74 link=board=5;threadid=19961;start=0#msg153417 date=1058158534]
Possibly one of the idle jets has something partially blocking it. Take out the needles (count the turns) and blow some air thru them then replace the needles. Might work, easy to do, and costs nuthin'.
[/quote]

I have never done any carb work. Any directions would help.
Thanks.

 

[GRIZZLY]

BC Broncos quadrajet.............

 

[Vin-Man]

Mine did that exact same thing about a month ago. Had the carb rebuilt and she runs fine now.

 

[BamaBronco73]

[quote author=Vin-Man link=board=5;threadid=19961;start=0#msg153498 date=1058191556]
Mine did that exact same thing about a month ago. Had the carb rebuilt and she runs fine now.
[/quote]
I am guessing that is my problem. Should I rebuild or buy new. If rebuild, who should I get to rebuild?

 

[Vin-Man]

[quote author=BamaBronco73 link=board=5;threadid=19961;start=0#msg153530 date=1058197784]
[quote author=Vin-Man link=board=5;threadid=19961;start=0#msg153498 date=1058191556]
Mine did that exact same thing about a month ago. Had the carb rebuilt and she runs fine now.
[/quote]
I am guessing that is my problem. Should I rebuild or buy new. If rebuild, who should I get to rebuild?
[/quote]

I had a local mechanic do mine. Carb kit and a couple hours labor, cost me a couple hundred bucks.

 

[wildbill]

8) 8) 8) I would say gey a can of carb cleaner and as was said take out the idle needles and spray carb cleaner in to hhe holes and put them back in and unscrew 1 1/2 turn and start the motor and then just turn untill runs smoth. Also spray some around the vac ports and ck. for a vac. leak good luck. : : : Bill 8) :

 

[BamaBronco73]

Not having dealt much with carbs....how obvious is the idle needle?

 

[Gordys74]

If you peek down under the front of the carb you should see two fairly large screws (one on each side of the front). These are the idle adjustment screws. They have springs on them to hold their position once they are set. These screws are formed into a point on the inner end and that point goes into the idle jets. Adjusting the screws in or out adjusts the amount of fuel the engine gets at idle. You can take them out without removing the carb and use air or carb cleaner, as suggested, to clean the idle jet. If you count the turns till loose, you should reinstall after cleaning the same number of turns and should be close to original setting. You may have to fiddle with them a little to get smooth idle.

 

[Wildturkey]

Did I read right when you said you dont have the vacuum advance hooked up on the distributor?Doesnt run real good does it and dies at idle?By all means hook it up before adjusting anything.

 

[LowerDixie]

Hey cuz, I been there, especially this time of the year in Alabama. I've got a new edbk carb and I still had problems. I'm pretty sure it was a fuel cook problem. I ended up wraping my fuel line in header wrap and bumping the idle screw 2/3 turn higher ( mine idles at 800rpm). I 'm sure my headers didn't help any , the heat and the humidity would cause vapor lock. I haven't had any problems since.

 

[Wildturkey]

If you are sure its still the carburator I picked one up at Advance Auto Parts a few months ago for about 125.00 I think it was.Just had to adjust idle screws a few turns.Only difference was the fuel line was inverted flare instead of stock carb fuel filter which is not a bad thing in that you can run bigger inline filter.

 

[BamaBronco73]

[quote author=Wildturkey link=board=5;threadid=19961;start=15#msg153806 date=1058237418]
Did I read right when you said you dont have the vacuum advance hooked up on the distributor?Doesnt run real good does it and dies at idle?By all means hook it up before adjusting anything.
[/quote]
Where does the other end go?