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Discussion Starter #1
Hello,
I Have 85 Bronco with a 300 I-6 engine that has recently developed a sputter when accelerating lightly @ low rpms. It however runs fine when accelerating firmly and when you get up to speed.. I'm not sure what to check.

The plugs look good and are a light tan color.
The plug wires are newer, same with cap and rotor.
Could it be bad gas?
Something stuck/ or wrong with the carb?

Any ideas for things to check would be greatly appreciated..

Mark
 

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Timing. OR Try replacing the fuel filter. Checking both will only help you anyways, so why not try the easy stuff first. Try one thing at a time and drive it to see what fixed it. But try the easy/free stuff first like I said before. Good luck.
 

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A fuel filter would most likely cut out more at high speeds, hard acceleration due to higher fuel demands, but it's always a good thing to check first and replace. There should be two if it's like my early 80's I6. One up in the engine bay either ON the carb, or near it, and one on the rail behind the driver's door. Replacing one when the other's plugged won't do much good.

Take the cap off the distributor and wiggle the rotor shaft. If there's a lot of play in it, your bushings are shot and the distributor's your problem. It's still sputtering at high speeds but you just can't notice it.

Also, I imagine you have all of the color coded brittle plastic vacuum lines? One of the best things I did with my I6 was to replace all of those with fresh, new, rubber vacuum lines. You'll need about 25' of it and a handful of vacuum T's. Those plastic lines can get hairline cracks in them (especially since by now they're all 25 years old), and you can't see them. But hundreds of hairline cracks adds up to a lot of vacuum leak. Replace all of them.

Has the carb ever been rebuilt? All the smog equipment hooked up? The '85 was in the era that the 300 had the computer controlled feedback carb and if something goes out, it won't run right. The computer adjusts the mixture and the timing and needs everything in top working order to function correctly (mostly why people retrofit the system with an older non-feedback setup.)
 

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Discussion Starter #4
Thanks for the replies so far.

It started acting up about a week ago, it starts fine and purrs like a kitten @ idle. It seems to sputter/stall more often when the weather is warmer.

One of the things I changed recently was, the 2 wires that connect to the primary side of the coil were very frayed and corroded, after several trips to auto part stores and not being able to find a replacement I cut off the click in connector and crimped on some standard connectors ... Could this be a problem? Any ideas on where to get the correct connector?

I checked the carb fuel filter and am going to look for the on the frame rail today.

the vacuum lines are all newer rubber, and haven't been messed with.

Any help or ideas appreciated.

Mark
 
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