383 intermittent misfire

[johnnycharger]

Hi guys
So I picked up a 70 D200 with a 383 about a month ago. Was running good but now it is incosistant. Sometimes I can drive it around town just fine and other times it looks like it is trying to run on 3 cylinders. It doesn't seem to be temperature dependant. Sometimes it idles smooth, I can rev it and it runs smooth but once it is in gear and try to pull away it sputters like mad.  It has new NGK plugs, pertronix wires, coil and ignitor. Have any of you seen this before? 

[Paul G]

Sounds like a cracked distributor cap. What is the ignitor? Is it an electronic ignition conversion?

[johnnycharger]

Thank you. Yes it is an electronic conversion. I will double check the cap.

[b5blue]

Clean the ground straps. If column ignition check the connector at the column, the big red wire is prone to overheating there.

[nvrbdn]

 

[johnnycharger]

Clean the ground straps. If column ignition check the connector at the column, the big red wire is prone to overheating there.

Good call. I started there and I cleaned all of the groud connections and that didn't fix it. The ignition is in the dash.

[c00nhunterjoe]

Not enough info to diagnose. But the line about idles and free revs all day long but sputters on accel could be as simple as ignition curve and carb transition circuit.

[johnnycharger]

I have capped the vacuum advance which made no difference. I am kind of grasping at straws with just enough smarts to get me in trouble :/

[johnnycharger]

Pulled a plug to check it and it is black.

[johnnycharger]

So the plugs are new (but now dead). It seems to be running bad all the time now. I will get new plugs but I need to figure out why it isn't getting spark. I will mess with the timing tonight.

[nvrbdn]

Did you check to see if each plug wire is firing? One of these testers will check the easy way. 12 bucks at Home Depot. I am thinking that since it was running good, then started falling off, is due to the look of the plugs.  Read through my thread I just dealt with. I am seeing the same with you. My first set of plugs I pulled were black. http://www.dodgecharger.com/forum/index.php/topic,133250.0.html  Check this out and see if you aren't pretty much running the same track.

[Paul G]

Do you have another ignition coil you can swap and try? Sure sounds like your coil could be dying a slow death.

[johnnycharger]

Did you check to see if each plug wire is firing? One of these testers will check the easy way. 12 bucks at Home Depot. I am thinking that since it was running good, then started falling off, is due to the look of the plugs.  Read through my thread I just dealt with. I am seeing the same with you. My first set of plugs I pulled were black. http://www.dodgecharger.com/forum/index.php/topic,133250.0.html  Check this out and see if you aren't pretty much running the same track.

I will look into getting one of those. I only checked one to see if it sparked. That is great info on the thread. I will check my float. Thank youď

[johnnycharger]

Do you have another ignition coil you can swap and try? Sure sounds like your coil could be dying a slow death.

Tried that last night. Thanks. I was thinking maybe it was bad out of box...

[johnnycharger]

Ok, I changed the plugs. I set the gap at .040. It started up pretty good and ran ok but not great. I adjusted the timing and it smoothed out a bit.
I checked the plugs again and they were already on track for being garbage after just a few minutes.

I hooked up the suggested in line tester and it looked to me like it was ok.
I attempted to check the float on the carb to see if it was stuck but the carb didn't come apart as I expected.  I pryed and pulled hard but but it didnt come apart.
I put it back together. Now it idles ok under no load but if you nail it it stumbles. Trying to drive it is a failure.
I have a hard time posting pictures here so I put the stuff on utube instead. I have posted videos of it starting, running, the spark plugs, ignition tester and carb.

https://youtu.be/Sgr7eTB_2Is

https://youtu.be/4PzKQGD5ud0

https://youtu.be/lKI3dQRjt10

https://youtu.be/4bQrE-PSd14

I appreciate all of your help.

[Paul G]

As for the carb, do you have new bowl gaskets for it? When you pull the bowls off I expect the gaskets to tear.

You can check the float level by removing the sight plugs on the passenger side of the bowls. You dont have to remove the bowls. When you remove a sight plug on the side of the bowl you should see fuel just dribble out. If fuel is pouring out, the float is set to high, float is sunk, needle not seating, or float is stuck. If no fuel is dribbling out float is set to low, or you have a fuel delivery problem. You can easily adjust float level, adjustment screws are on the top of the float bowls on each bowl. Watch the video below.

https://www.youtube.com/watch?v=LKEonVeOXco

Sounds to me like it would be a good thing right now to pick up a carb kit and rebuild the carb. If your ignition is good, which it appears to be, next thing is the carb. 

[krops cars]

Did you check the air gap between the module and the reluctor wheel that mounts on the dist. shaft. When we install these I know that is necessary. Plugs also show a rich run condition.

[BLK 68 R/T]

PCV valve sticking open sucking lots of oil?

[johnnycharger]

quote author=krops cars link=topic=133326.msg1656000#msg1656000 date=1534519821]
Did you check the air gap between the module and the reluctor wheel that mounts on the dist. shaft. When we install these I know that is necessary. Plugs also show a rich run condition.

1534520502] yes I did. Thanks.
PCV valve sticking open sucking lots of oil?
[/quote]

Nope. But thanks.

As for the carb, do you have new bowl gaskets for it? When you pull the bowls off I expect the gaskets to tear.

You can check the float level by removing the sight plugs on the passenger side of the bowls. You dont have to remove the bowls. When you remove a sight plug on the side of the bowl you should see fuel just dribble out. If fuel is pouring out, the float is set to high, float is sunk, needle not seating, or float is stuck. If no fuel is dribbling out float is set to low, or you have a fuel delivery problem. You can easily adjust float level, adjustment screws are on the top of the float bowls on each bowl. Watch the video below.

https://www.youtube.com/watch?v=LKEonVeOXco

Sounds to me like it would be a good thing right now to pick up a carb kit and rebuild the carb. If your ignition is good, which it appears to be, next thing is the carb. 

Great thinking.  I don't know why I spaced about the site plugs. Thank you very mich for the information and the link. A rebuild is in the near future but I want to be able to drive it to the windsheild shop tomorrow if possible.  I will try this tonight.

[Paul G]

There is lots of info on rebuilding a Holley on youtube.

[Paul G]

Seems like everyone has missed the first and simplest question.... are you sure the Choke is fully open and staying open?

[johnnycharger]

Seems like everyone has missed the first and simplest question.... are you sure the Choke is fully open and staying open?

The choke is not connected so it is wired open by the previous owner. It was about halfway closed. I made it all the way open last night when I was messing with the carb.

[Paul G]

Seems like everyone has missed the first and simplest question.... are you sure the Choke is fully open and staying open?

The choke is not connected so it is wired open by the previous owner. It was about halfway closed. I made it all the way open last night when I was messing with the carb.

Have you driven the truck yet? I am curious to see if the choke closing was causing the issue?

[c00nhunterjoe]

Choke is visibly open in the one video, said its wired open. Before you go rebuilding the carb, you need to find out what is wrong with it 1st. Most rebuilds are just gaskets and a needle/seat. Could be anything causing the problem.

[XH29N0G]

Quick thoughts - bc the people you have responding already will give good advice and know more than me.

If you mostly idle, the plugs can get dirty pretty quick and foul.  I have been able to clean and run them without replacing. I am sure you know that already.

I believe your ignition is OK.  I had mine cut out intermittently because of a poor connection at the firewall, and I often have suspected at the battery.  I have also had a coil warm up and do this.  My guess is that these are not your problems.

Re the carb and timing:  Have you adjusted the idle mixture with a vacuum gauge (vac advance unplugged) after the car is warmed up?  This might be part of the dirty plugs.  Also, have you adjusted the timing (vac advance unplugged) after the car is warmed up.  I found with my car that advancing the timing to where it idled most smoothly and the idle speed stopped advancing with timing (the issue with running higher initial is the full advance curve - which you don't want being too high) and then after that, I reset the idle speed screw and then readjust the idle mixture using the vacuum gauge.  For my car, this helped keep plugs cleaner because it ended up being a leaner setting.  They then stopped fouling and the idling did not lead to an eventual misfire from fouled plugs.  My inclination would be to see if any of this helped and then work from there.  Stumble and other issues will be outside the idle circuit on the carb. Those can be dealt with once you are satisfied with the idle.

If someone posts and says this is not the first thing to check or there is something else.  I would go with that over what I have suggested.

   

[johnnycharger]

Hi All
Ok so today I checked the fuel level through the site plug. It was good. I hooked up a vacuum gauge and tried to adjust the air fuel mix. I started at the default of 1.5 turns out like stated in the Holley video. When I adjusted the screws I really didn't see much change. How far do you need to turn it before it affects the vacuum?
I looked down the carb while it was running. I noticed the "butterflys" were completely closed. It is also very loud. Sounds like it is struggling to suck in air. The butterflies looked like they had condensation on them. I don`t know if it was gas or not. It is running smooth except for if I stomp on it. It has a momentary hesitation then it goes. I drove it for 2 miles, looked in the carb again- now the butterflies are dry. Pulled a plug and it was dry and black. I don`t know why they are black again.

[johnnycharger]

Quick thoughts - bc the people you have responding already will give good advice and know more than me.

If you mostly idle, the plugs can get dirty pretty quick and foul.  I have been able to clean and run them without replacing. I am sure you know that already.

I believe your ignition is OK.  I had mine cut out intermittently because of a poor connection at the firewall, and I often have suspected at the battery.  I have also had a coil warm up and do this.  My guess is that these are not your problems.

Re the carb and timing:  Have you adjusted the idle mixture with a vacuum gauge (vac advance unplugged) after the car is warmed up?  This might be part of the dirty plugs.  Also, have you adjusted the timing (vac advance unplugged) after the car is warmed up.  I found with my car that advancing the timing to where it idled most smoothly and the idle speed stopped advancing with timing (the issue with running higher initial is the full advance curve - which you don't want being too high) and then after that, I reset the idle speed screw and then readjust the idle mixture using the vacuum gauge.  For my car, this helped keep plugs cleaner because it ended up being a leaner setting.  They then stopped fouling and the idling did not lead to an eventual misfire from fouled plugs.  My inclination would be to see if any of this helped and then work from there.  Stumble and other issues will be outside the idle circuit on the carb. Those can be dealt with once you are satisfied with the idle.

If someone posts and says this is not the first thing to check or there is something else.  I would go with that over what I have suggested.

   

Thank you for the good suggestions.

[johnnycharger]

https://youtu.be/dPmuvoWyA7Q


Here is what the carb sounds like. I can hear it louder than the exhaust. Is this normal?

[nvrbdn]

If you can totally cap off the air draw through the carb and not stumble the engine, I would say you have a bad vacuum leak somewhere that is drawing major air. Either a rotted hose, or the gasket under the carb. Check for any vacuum ports on the carb that are open, or a leak in a vacuum hose, power brake booster, anything drawing vacuum from the manifold.

[c00nhunterjoe]

   but that will go terribly lean, and your plugs are wet and fuel fouled in minutes. Massive vaccum leak and over rich.

[johnnycharger]

So tonight I looked for a vacuum leak and had no luck. I looked over the carb and vacuum lines and found no signs of a leak. I also sprayed carb cleaner on the lines and gasket surfaces as well as the manifold fittings and had no luck.

[krops cars]

When you put your hand over the carb it should have died or idled  lower. I did not here any real difference. I agree nvrbdn try a vacuum gauge. You should have 18 to 22 inches of vacuum. Let us know what you have. Do you have another carb to try? Also. How old is the fuel? You maybe trying to chase something that might not be the issue.