Idle problem

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George R

George R

Mopar Nutcase
Joined
Oct 29, 2007
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Location
Trumbull, CT
Hi guys.
I ran the Dart 600 miles round trip from Connecticut to Carlisle and back and it ran like a clock. About 75 miles from home I stopped at Sonoco for gas and bought the 91 octane fuel. Once back on the highway I noticed the car pinging slightly going up hill at cruise speed. It didn't ping at all before this.
If I stepped on the gas harder the ping would stop as the vacuum advance would retard the timing from the throttle position. Anyway, didn't think anything of it. Once I got off the highway near the house, the car has a rough idle as if it is only firing on 7 cylinders. As soon as you touch the gas it smooths right out and runs great. It is only the idle that is affected. I also noticed the power brake pedal is harder to press. Maybe engine vacuum is low due to the dead cylinder at idle?
I still have 1/2 tank of that fuel in the car. Do you think it is bad gas, or did I ruin a plug or something? Should I screw around with it or just top it off with gas from another station locally and see what happens, or..??

Any help appreciated. I gotta have it fixed for Adam's party on Saturday! :D

George
 
I would just add some water remover,nowadays scammers are adding water to the gas.When you add gas it pushes water to the bottom,your probably sucking some water with gas?My 2 cents.
 
I'll try topping it up with fresh gas from the local station where I usually go for gas.
Any other suggestions as to why it seems to idle on 7 cylinders now? Should I replace the plugs, or does it sound like a carb problem??

Thanks fellas.

George
 
I would definitely put a couple bottles of dry gas in it before topping it off to bind up the water if that's what is causing the problem. Also, I wouldn't go replacing any parts until you get another tank of gas.
 
Most likely you got some bad gas. Years ago I had a similar problem but worse than you described. After filling up the car wouldn't pull any sort of a hill faster than 40 mph, felt like it was running on 4 cylinders. After a couple of bottles of gas line antifreeze as we call it up here in the north, all was well again.
 
I think the problem is the vacuum booster for the power brakes. It pulls vacuum from cylinder #7 via the port on the intake runner. I clamped the booster hose off and the misfire was gone, and the idle speed went down.

Trying to find out if the boosters for a 70 Duster with front disc brakes is the same as my 69 Dart with 10" front drum brakes as I have another booster here at the house.

Thanks for the help, guys. Appreciated.

George
 
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