Hi everyone. It's been a while since I've been on here and I need your help. I'm getting my car up and running again after it sat for about 2 years. I'm having a problem with the idle dropping, which eventually causes it to stall. Engine is a 225 slant six with a single-barrel Holley 1920 carb. The car has 104,000 miles. All components are original or stock replacement parts. No internal engine work has been performed on it.

So anyway, I had the carb rebuilt by a reputable shop who was recommended by 2 different mechanics from 2 different shops. I bolted it back on and fired it up, but it ran rough, backfired, stalled out, etc...... after checking all ignition components, timing, points and carb settings, it turned out that i had a dead cylinder #6. Lucky for me it ended up being a pushrod sticking out. My mechanic fixed it, i bolted the valve cover back on, made connections and it's singing smooth and responsive again.

My only problem now(with exception to some frame repair needed) is that the idle will drop really low to the point where the engine sputters. It will come back to normal idle, then a min or so later, it will drop n sputter, then come back to normal....this process repeats until it drops, sputters and cuts out. If you try to pump gas while it drops, it usually doesn't make much difference, but sometimes you can catch it and get it to rev up smooth. Eventually though, pumping the gas does nothing and the engine cuts

As I've said, I just had the carb rebuilt. I've put a new distributor, cap, rotor, plugs, wires, fuel filter.....everything but an ignition coil. 2 mechanics from the same shop said that maybe the coil isn't putting out consistent spark and is causing the drop.

My questions are.....A) Does this sound like a symptom of a bad coil?....and B) When replacing the coil, will putting in a high performance coil have any negative effect on the rest of the system? I don't mind paying more for some better performance and reliability and I saw an MSD performance coil available at NAPA.

Let me know what you all think and as always, thanks so much for the good info.

I think you have a sanitation problem. Your freshly rebuilt carburetor is most likely suffering from dirty tank syndrome and its idle circuit has some fine rust or varnish starting to build up blocking fuel flow.

Did you run some old gas through the rebuilt carburetor?

Did you clean out fuel line before installing rebuilt carb?

Has the fuel filter been replaced?

Did you drain out the old fuel from tank and refill with fresh, or just dump in some new to mix with the old fuel?

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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

Thanks for the reply. Bad fuel was the only other explanation that my mech gave me as well. No, I did not use fuel stabilizer and did not drain the tank. I did not drain the line or anything. The fuel filter was replaced a couple of years ago, but doesn't have many miles on it. I just fired it up with what was in there - a full tank (less about 1.5 gallons) of 2 year old 87 octane gas with no additives. I'll try and drain it on Monday and let you know how I make out. Once I fill it with new gas, is there anything else that i should add to clean the system out? Thanks again.

Ah ha! The old stale gas trick 99...

I would detach the soft line at the tank connecting it to fuel line and at pump and blow some air through it to purge all the crap it may harbor, and replace with new soft fuel injection line that has the inner liner which resists degradation by todays fuel do the same for connections at pump filter and carb. Replace the fuel filter, it had fuel in it that evaporated leaving behind varnish and particulate even though it has little mileage or use it is contaminated. While you are at the tank/fuel line connection I would renew the sending unit ground jumper to insure good fuel gage operation.


The tank is another thing it could possibly have a good coat of rust from that old alcohol laced fuel sitting exposed to the air for two years, yes air, as the pre 1968 or 69 or 70 fuel tanks (can't recall when closed loop systems came on line) were direct vented to the air via a tube terminated within the driver's side rear frame rail. But, before you go yanking the tank, I suspect that where the tank was almost full there was not a lot of air to trap humidity as the weather goes from dry to wet, and you may be ok with just draining the old fuel.

One thing you can try is once you have fresh fuel to the carburetor carefully back out the idle mixture screw one turn, or more turn paying attention to just how many turns to be able to set it back where it was, and blip the throttle a few times and reset the screw to where it was. Sometimes crud will hang up at the needle point restriction and once opening is enlarged crud will pass.

If messing with the idle mixture is unsuccessful in restoring a good idle you may have to open up carburetor and blow out passages of idle circuit, and main jets. You may also find running the car for a few days will clear up the idle problem.


So a few little things to address:
Clean fuel line, replace soft fuel line couplings, change filter, drain tank, and clean carburetor as needed.

Maxwell Smart

_________________
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

Thanks again for the replies. Here's where I am......

I siphoned out all of the gas(as much as I possibly could). Mechanic checked the gas that I drained and said that it looked and smelled okay. I put 15.6 gallons of 93 octane in there anyway, filling it. I ran it and same thing...real responsive and smooth, but then idle drops, sputters and runs rough. Wasted $55......

So then I replaced the ignition coil.....fired it up....same thing.......another $50 wasted.

At this point I've replaced every single major electrical component, rebuilt carb and ran fresh gas........ Could it be some little resistor or something? What is the stock points setting? I want to confirm that my mechanic has them set right.

I'll try the idle screw trick and the other things mentioned. If it was the fuel filter, wouldn't the sluggishness and sputtering be consistent?

You mentioned the sending unit. My gas gauge does not work and I believe it works off the sending unit. Would this be part of the problem?

Any other ideas? I'm totally lost and going out of my mind throwing time and money at this problem. Every time I think it's all figured out, I find myself in the same position. Any and all help is greatly appreciated. Thanks.

No, that is a separate from drivability electrical problem that can be addressed in the electric heading of this site. Best to keep problem discussion to one at a time per relevant heading for simplicity and clarity.


I still cast a vote in favor of crap in the carburetor's idle circuit.


I estimate your fiduciary over exuberance at about 5 bucks, the amount one would have coughed up to step up to 91 from basic rotgut 87 octane; you were going to fill'er up sometime anyway.

_________________
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

Make sure your distributor vacuum advance is hooked up to the upper port on the carb. This is the one above the throttle plates. If it is hooked to the lower one, it will go into cycles like you describe. Say a small contaminate briefly limits the fuel flow: then the idle drops a bit and so does the timing at the distributor, which further drops the vacuum, which further drops the timing which further slows it down, which further drops the timing etc. until it dies.

Sam

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Hi all. I finally got the car running. All of the fuel system checked out. It ended up being internal to the distributor. My friend replaced the points and resistor, dialed it all in, checked timing and it came back to life. When he pulled the distributor out, he found the vacuum advance module to be bad(that was just replaced earlier today). I found my ballast resistor on the firewall was blown also, so I replaced it as well. Total parts was less than $50 I think. I also replaced the rotor since it was already ordered and also inexpensive.

While it was there, I cut out the 6" x 9" speaker holes behind the rear seat, mounted the speakers, some subs in the trunk and some 2-way speakers to the kick panels in front, sitting the tweeters on top of the dash. I know it's a little bit ghetto, but it's basically all out of sight anyway. I'm going to mount my stereo to a simple center console setup because it's a fold-out DVD player and it won't work right under the dash. The glove box doesn't open correctly and it would be annoying to lean over and change stations, etc.....plus the fold-out problem.

The day we got it running, I drove it directly to another friend's auto/auto body shop for the welding. It was done by the next afternoon. Charged me $100. I feel like I'm ripping him off, so I'm going to buy him lunch and do some minor website work for him. I'm getting my money together for insurance, registration and inspection now. It should be rolling reliably and legally within a couple of weeks.

Hopefully this will be the last of my engine problem posts for a while. Thanks again for all of your help and good luck with your autos.

If it will make you feel any better about the fuel... regardles of how it smelled, the #6 pushrod being out is probably due to the old gas varnishing a valve guide and the valve sticking a bit and letting the pushrod fall out. (Especially if it was the intake pushrod.) These don't fall out by themselves. 2 year old low lead fuel in this day and age is well on its way to being bad, so IMO consider yourself to be fortunate to get that old gas out. I have ruined a 4 cylinder 151 ci engine with old gas, with the valves so badly sticking as to break a rocker when the pushrod got out of whack.