Bad engine stumble
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Pro
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From: Flakewood Wrench, FL
Bad engine stumble
Since getting my 66 300 hp coupe out this year, I have been noticing a slight stumble both on acceleration and at cruising speeds. Nothing major but a slight miss, a little bump, some hesitation. But it got progressively worse, so much that on the short return ride home last night, it started to stumble so much and so hard, my wife and I felt like we were riding a badly behaved horse. It lurched, bucked, the engine felt like it was cutting out then re-igniting. We made it back home but it got worse and worse the longer we drove it. A short back story: 2 years ago I replaced the points, rotor, cap and condenser with new. Also, in October of last year, for the first time in ages, filled up with non-ethanol fuel. This just came out of the blue. I've checked the threads here and see a lot have to do with newer years. Any thoughts on this is appreciated.
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Does it stumble/hesitate only when you try to accelerate? Or is it stumbling during steady throttle?
Does it feel that that the engine wants to stall and then comes back to life?
Joe
Does it feel that that the engine wants to stall and then comes back to life?
Joe
Team Owner
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Army
I think he is saying it stumbles at cruising speeds too Joe...but he can confirm.
A few quick things to check (most likely not accel pump on carb if it does it at cruising speeds):
Fuel filter/fuel pump output
Make sure distributor hold down bolt is tight
Distributor cap/rotor/plug wires (and routing) - points/condenser/coil
A few quick things to check (most likely not accel pump on carb if it does it at cruising speeds):
Fuel filter/fuel pump output
Make sure distributor hold down bolt is tight
Distributor cap/rotor/plug wires (and routing) - points/condenser/coil
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Trouble is, as simple as our old cars are to fix, they are not at all simple to diagnose in that many, many different problems can cause the same symptom.
It is just as possible your carburetor is dripping because of a bad accelerator pump or a stuck needle and seat or a sunken float, all of which could cause the symptoms you report.
While running and being careful where you put your hands and necktie, have the air cleaner off and look down the throat of the carb for dripping fuel and/or a gurgling sound.
Dan
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From: Greenville, Indiana
Check the points gap. Pull the ignition cover off the distributor and see how it runs. Drain a little gas out in a clear jar and look for water settled in the bottom of the jar or even a hazy mixture.
Check for bad connection at the firewall on the big red wire at the bulkhead connector.
Check for bad connection at the firewall on the big red wire at the bulkhead connector.
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From: Flakewood Wrench, FL
I haven't
gotten into this yet but later tonight I'll start running through the culprits mentioned above. I'm not sure if it's fuel or ignition related as some symptoms are similar. As I mentioned before,it started out very subtle the 1st time out for the season. Then second time out, it got progressively worse until it refused to run without cutting in and out. No backfires, but it bucked like a horse. I thought the fuel gauge was broken and that I was running out but I looked in the tank and it was good. Did put new plugs and wires on maybe 15+ years ago. I drive this maybe 200 miles a year. It's got to be something simple.
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Safety Car
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gotten into this yet but later tonight I'll start running through the culprits mentioned above. I'm not sure if it's fuel or ignition related as some symptoms are similar. As I mentioned before,it started out very subtle the 1st time out for the season. Then second time out, it got progressively worse until it refused to run without cutting in and out. No backfires, but it bucked like a horse. I thought the fuel gauge was broken and that I was running out but I looked in the tank and it was good. Did put new plugs and wires on maybe 15+ years ago. I drive this maybe 200 miles a year. It's got to be something simple.
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From: Flakewood Wrench, FL
The coil
is an old 202 that's been in the car since I bought it in the mid 80's. It may be the original given when I replaced the plug wires years ago, they were original. I'm going to bench that tonight or tomorrow (not retired yet 
) and am interested in the resistance reading it will give. Anyone know what value I should be looking for in a good 202 coil?
) and am interested in the resistance reading it will give. Anyone know what value I should be looking for in a good 202 coil?
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From: Flakewood Wrench, FL
Found some oil on the intake just below the carburetor on the passenger side tonight as I removed the air cleaner and shielding to get to the coil. Also the intake bolt in that location that also holds the clip for the vac advance tube, was not as tight as I would expect- I tightened it further with a wrench. Not good but don't know if it's related.
Thread Starter
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From: Flakewood Wrench, FL
is an old 202 that's been in the car since I bought it in the mid 80's. It may be the original given when I replaced the plug wires years ago, they were original. I'm going to bench that tonight or tomorrow (not retired yet ) and am interested in the resistance reading it will give. Anyone know what value I should be looking for in a good 202 coil?
) and am interested in the resistance reading it will give. Anyone know what value I should be looking for in a good 202 coil?
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It could be the coil but when a coil is failing it normally will not start or causes miss-fires during acceleration.
Try disconnecting the vacuum advance.
I had a couple of cars with the same symptoms.
When cruising the vacuum advance would move the breaker plate and the primary wire, which was chaffed, causing it to hit ground, momentarily shutting off the ignition, and when the vacuum dropped off, the plate would move back to the rest position and the wire would become ungrounded. Then the engine would fire back up causing the vacuum advance to move again and the cycle would repeat itself. It worth a try and costs nothing.
Joe
Try disconnecting the vacuum advance.
I had a couple of cars with the same symptoms.
When cruising the vacuum advance would move the breaker plate and the primary wire, which was chaffed, causing it to hit ground, momentarily shutting off the ignition, and when the vacuum dropped off, the plate would move back to the rest position and the wire would become ungrounded. Then the engine would fire back up causing the vacuum advance to move again and the cycle would repeat itself. It worth a try and costs nothing.
Joe
Burning Brakes
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From: MANCHESTER IOWA
my 64 vette was doing the samething. so i cleaned the carb up. still did it. changed coil. still did it. finally i changed the distributor to an old one i had around and now its running great. so i'm sending it to Lars to rebuild.
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From: Flakewood Wrench, FL
Finally
got a chance to look into thus issue in depth. What I've I found thus far is the accelerator pump leaking fuel when asking for more. The electrics seem very good but fuel pours out from the bottom of the front bowl when the pump is engaged. So I'm going with a fuel issue right now. The carb is a 3367 replacement that's been on since '88. I had the original rebuilt some time ago and stored it. Seems like the right time to put it on. I'm going to rebuild the fuel pump. It's original too; I rebuilt it the same time I swapped carbs in '88 so it might be ready for another. Any thoughts on the place to get a rebuild kit these days.? Last one I got was from Dr. Rebuild. I'll look around.
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From: Greenville, Indiana
got a chance to look into thus issue in depth. What I've I found thus far is the accelerator pump leaking fuel when asking for more. The electrics seem very good but fuel pours out from the bottom of the front bowl when the pump is engaged. So I'm going with a fuel issue right now. The carb is a 3367 replacement that's been on since '88. I had the original rebuilt some time ago and stored it. Seems like the right time to put it on. I'm going to rebuild the fuel pump. It's original too; I rebuilt it the same time I swapped carbs in '88 so it might be ready for another. Any thoughts on the place to get a rebuild kit these days.? Last one I got was from Dr. Rebuild. I'll look around.
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From: Flakewood Wrench, FL
How these things go...
I replaced the carb with the original 3367, rebuilt and restored. It's still running a little wild but while it was up on stands I decided to take care of some things that have been on my list. The front and rear main seals have been leaking for some time. I noticed while apart the balancer has a groove in it worn in from a hardened seal. The timing chain has enough play to warrant replacing. I got a new Felpro rear main seal and am curious as to what timing chain set to buy. Any thoughts on which sleeve to buy as well. I only want to do this once. Still looking for a rebuild kit for a 4657 fuel pump. Paragon no longer has them. Any ideas here? As long as the pan is off I want to replace the oil pump. Thinking of a Melling high volume. Also, the original AL radiator has an area that shows leakage. Can these be repaired? It's been suggested I throw a can of some new miracle sealant. or do I bite down hard and call Dewitts? Any help is appreciated.