1972 350 Surging Under Load When Stopped and at Operating Temperature

Well, gang, eliminated a couple possibilities.. replaced the coil, and while doing that, I found that the red wire going to the positive side of it was broken. For the time being, I've taped it. The wires are no longer glowing, but just took the car for a drive, and it's still doing the same thing. It ran great for the first 10 minutes or so, then started acting up again. I checked gas cap as well, took it off, no difference.

 

Stick with it, it’s going to end up being something simple. Did you recheck points and timing?

 

How is the choke for the carb? Is it properly adjusted? How about the cold idle screw adjustment? I had some serious stumble when these weren't correct.

 

Also check the choke pull off to make sure it is functioning properly. Back in the day in H/S Auto shop class the most common thing that went bad on the Q-jets was the choke pull off that made the cars run crappy.

 

I'll check each of these tomorrow, guys!

 

It's a hesitation when I step on the gas, but it's not dying out, no. When it gets all warmed up, it starts misfiring while idling in park/neutral, and when it's stopped and in drive/reverse, it kind of shutters and runs badly, and it'll kind of jerk the car forward a bit even with brakes applied. Again, giving it gas from a stop, it cuts out intermittently until I get up to speed. I believe it's misfiring at cruising speed, too, but it's hard to tell with noise/engine speed. Sorry for not being clearer.. I'm still pinpointing how to word what the problem is.

 

So not really surging from load only. Horrible throttle response in the driveway also?

 

Correct, sir. And, I haven't checked the dwell/gap yet, so I'll do that tomorrow. To be completely honest, I've only messed with points once before, and that was on my mom's Beetle, so I have some more learning to do on that front.

Yep, as it approaches fully-warm, it starts to misfire worse and worse. It never gets to the point where the car dies, but it's not very drive-able at that point.

 

I had a cracked head on my Toyota 4.6 V6 and it behaved just like your car.

 

Whoa boy. I'm really hoping that's not the case. Would I see smoke or something?

 

That was on an alum head. I'm still thinking yours is carb related. Did the former owners give you any clues?

 

I'm thinking carb, as well, but I'm definitely going to go through all of the systems / ideas that have been mentioned. The previous owner said it ran great all last summer, and he stored it back in October until I bought it. I doubt he knows anything about this issue, but I'll shoot him a text tomorrow to see if he ever noticed anything like that.

 

About to pull plugs to take a look, I checked the Q-jet filter.. is there supposed to be a check valve for this particular carb? It has the spring, the filter looks OK, but no check valve.

 

Ok cool.. here are 4 of the plugs from drivers side.. looking pretty black on a couple:

 

you running a little rich there ..clean em all up ...start her up

then try looking down the carb when its bogging on you and check for dribbling fuel /flooding

if none...... we check fuel pump .....disconnect your fuel line by filter and get a container and have someone crank the engine -no start just crank -
and If I am correct its suppose to get a pint in about 30 seconds...this is volume check

if your vacuum gauge does fuel pressure then do a pressure test ...crank for 20 seconds 4-6 pounds



no worries ...with this long distance help on forum we all gonna make a
master diagnoser out of you