Car dropped 250 RPM and is now stuttering

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You have to unplug the vacuum advance from the distributor and plug that port on the carb to check total mechanical advance.
 
Before you do a lot of testing, plug changing, etc. run some good gas through your engine and see if it cleans it self up. This is experience speaking. Years ago, I got a bad tank of gas in Houston and no way to check anything. By the time I got home near Dallas and filled the car up it had cleaned itself up.
 
I'm not able to play the video cause my phone's lame on data and won't stream vids very well at all.
Have you checked you alternator. Sometimes it won't put out enough voltage to run the car right but just enough to keep it alive
 
Phily said:
I'm not able to play the video cause my phone's lame on data and won't stream vids very well at all.
Have you checked you alternator. Sometimes it won't put out enough voltage to run the car right but just enough to keep it alive
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Well I have been taxing it since installing the MSD box. But it has been running fine up until now. I'm not sure why all the sudden it would just change.
 
6 months. Never had an issue with it. I don't buy that all the sudden something would have changed.

I will look up how to test it but I doubt it's it.
 
A fellow Mopar enthusiast came over and we took at look at the engine. He is fairly certain that I have a vacuum leak causing a leannout situation.

The engine rev healthily and the idle comes back when the butterfly is closed up. Without closing the butterfly the car will sputter and die.

I'm going to spray around the typical areas to see if I can find a leak.

Not sure if this matters but I recently switched from two breathers to a PCV. The carb was retuned for the PCV.
 
WSUTARD said:
I don't buy that all the sudden something would have changed.
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But it apparently just did or there wouldn't be a problem all the sudden.
Don't take anything like that for granted, and see if what I suggested to do helps.
2 minutes out of your life to try it.

Or don't.
WSUTARD said:
A fellow Mopar enthusiast came over and we took at look at the engine. He is fairly certain that I have a vacuum leak causing a leannout situation.

The engine rev healthily and the idle comes back when the butterfly is closed up. Without closing the butterfly the car will sputter and die.

I'm going to spray around the typical areas to see if I can find a leak.

Not sure if this matters but I recently switched from two breathers to a PCV. The carb was retuned for the PCV.
Click to expand...

Or it has something in the jets and what I suggested will clear it.
Just because it's apparently running lean doesn't always mean too much air.
It can also be from not enough fuel.

Rev it up a bit and then throw it wide open while closing the choke all the way until it dies down and then let off both in time for it to recover.
Give it a little rev or two to clear out the extra fuel and smooth out.
Better, or problem gone?
 
I reved it up and then blocked it off a few times. No change.

I sprayed for a vacuum leak, nothing.

I opened the valve covers, no bent anything.

I did notice the oil sitting on the top of the rockers looked weird. It looks like oil that you get when you break in a cam. Which is what I did about 100 miles ago. I broke the cam in and then changed the oil. I'm guessing what I am seeing is residual from that cam break in. You can see the "cloud" in the picture below.

At this point here is exactly what it is doing.

Idles at 400, the carb idle is set to 750.

While idleing if you close off the butterfly it increases the revs.

When you release the butterfly's back the idle drops down and the engine dies.

It revs healthily. It is not missing a piston.

It revs its self up when a little gas is provided. Example would be taking it from idle to 750 rpm it will actually over rev up to 1250 once it grabs some gas and air.

When at higher rpms it will bounce up and down. Example, hold throttle at 2000 and it will bounce up to 2500 and back down on its own.

The gas is good.
It starts reliably.

My next step is to take the carb off and open it up looking for junk. Last time I opened it up it was very clean inside. The gas tank is new. There is now sign of crap in the fuel filter.

I'm going to change out the carb plate and spacer gaskets when it take it off.

IMG_2016.JPG
 
Regarding the MSD, I'm having a hard time finding instructions on how to test it. It is turning on, its starting the car, it isn't losing power. I'm at a loss as how to "test" it.
 
I'd still check the alt and battery. Takes 2 min
 
WSUTARD said:
No burnt plugs or wires.
How long till the water separates from the gas?
View attachment 1715049515
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LOL, instantly, if it's in that sample it would be on the bottom of the jar already. If it were emulsified or combined w/the 10% of alcohol mandated, it would be cloudy and
would be seen obviously settling out and gathering at the bottom of the jar.
 
Phily said:
I'd still check the alt and battery. Takes 2 min
Click to expand...
I used a multi meter to check the voltage at the battery. Everything is at spex.
12.8 resting
14.10 running
13.8 with a load

Anything else I should do to test the alternator?

One of my buddies suggested to check the fuel pressure so I slapped on a gauge. 7 psi steady.

I guess it's on to taking off the carb and opening it up looking for blockages.
 
Did you go back and plug the vacuum line to the distributor vacuum advance and check the advance at 2200 RPM, as well as at idle?

Your battery and electrical system voltages look normal. Now just check one more spot: voltage into the MSD unit.

Set the engine at TDC and remove the distributor cap, and make sure the rotor is pointing directly at either #1 or #6 spark tower. Look under the cap and at the rotor carefully for any odd appearance.

Use a vacuum gauge and look at the vacuum in the intake manifold at 'idle'.
 
Dont just plug the vac advance, take it completely off the dist. I had a buddies car doing the exact same thing, the vac arm was causing a binding. Took me about a week before I threw my distributor in and figgered her. It was an accel or msd unit.
Its not bad gas lol.
 
nm9stheham said:
Did you go back and plug the vacuum line to the distributor vacuum advance and check the advance at 2200 RPM, as well as at idle?

Your battery and electrical system voltages look normal. Now just check one more spot: voltage into the MSD unit.

Set the engine at TDC and remove the distributor cap, and make sure the rotor is pointing directly at either #1 or #6 spark tower. Look under the cap and at the rotor carefully for any odd appearance.

Use a vacuum gauge and look at the vacuum in the intake manifold at 'idle'.
Click to expand...

Are you talking about the voltage going from the battery to the MSD or from the bulkhead to the small red MSD wire?

I did have the carb tuning shop put the FBO plate in the distributor. Maybe they messed up somehow and it just now made a difference.

skizzo said:
Dont just plug the vac advance, take it completely off the dist. I had a buddies car doing the exact same thing, the vac arm was causing a binding. Took me about a week before I threw my distributor in and figgered her. It was an accel or msd unit.
Its not bad gas lol.
Click to expand...
Skizzo, when you say "take it completely off" do you mean get a distributor without a vac advance?
 
Check the voltage at the MSD running. There are a few places where you can get some voltage drop and you just want to be sure it is near to the voltage level at the battery.

Unless the FBO plate moved, then it would not 'just show up now'. Please re-check the timing advance with the vacuum advance hose pulled and plugged. Your 50 degrees advance at 2200 is a problem but the vacuum advance is in the way of getting the right data.

You need a solid baseline of info for cranking compression, vacuum at idle, and timing advance at various RPM's for future work and troubleshooting.
 
I tested the timing and the vacuum.

700 rpm 12 advance
2200 rpm 32 advance
2200 rpm with vac advance 52 advanced

Vacuum at 700 is 7. Prior to this issue it was just over 10.
 
Also, I just noticed a tick at about 1000-1200 rpm with the vac advance connected and didn't notice it with it disconnected.

It's hard to hear if it's present at more rpm due to the noise of the engine and exhaust.
 
Found time to look at the distributor. I can't see anything out of the norm.

Here is a vid of its movement. Sorry about the vertical video.
 
I'm breaking into the carb now.

Isn't there supposed to be some kind of boot on the accelerator pump?
IMG_2026.JPG
 
I am probably the least qualified here to diagnose your problem but could it be the coil going bad?
 
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I took it all apart, cleaned it, blew out the channels. Nothing to see here.

Still looking for the issue.
 
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