My 1986 Dodge D150 pickup has the 3.7L slant six and auto transmission, new Holley 1945 carb, new spark plugs, wires, distributor cap, insulated fuel line, new fuel filter, intake and exhaust manifolds. The idle is perfect most of the time. However, after it is warmed up it will sometimes develop a very rough idle. Then in a few miles it will go back to a smooth idle. I have checked all of the plug wires and they fit tightly. I have put new gas in the tank. Sounds like it may be trash in the main jets of the carburetor. What do you suggest?

Might be the EGR valve is hanging up a little.

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

I second the EGR valve. My '87 318 with Holley 1920 (yes I know not /6) had rough idles and would have some rough acceleration as well. When I disconnected the hose from the carb to the EGR (and plug the hose), the problem went away.

Hope that helps.

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~Less think, more do

You may have a few water droplets in the bottom of the bowl that will occasionally restrict flow at the jet. Some gas dryer may help especially in the winter months. I run a fuel water separator which stops that from happening. You can click on the red link below to see my installation. It was one of the first things we would install on a boat or diesel truck. Why not our cars? Some older gas stations pump some pretty bad fuel.

If you used any 30R7 fuel line, it melts and disintegrates with the new ethanol fuel blends. You may have some debris floating around in the bottom of the bowl as well. 30R9 fuel line is much better.

Double check your voltage at the coil and valve lash if your engine is transplant, like an older solid lifter motor.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

OK here is a stupid question. With all the Ethanol in gas these days do we really need to by more (gas dry)?

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

For some reason that 10% fuel blend exacerbates moisture collecting in fuel. Also, fuel sitting for much more than a month or two can give problems with water separating out.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC