miss at highway speed with steady gas pedal

[saylor]

at 70 on the highway, with a steady gas pedal open just enough to maintain same speed, I could feel a stutter/miss/burp/fart/surge something happening. if I gave it more gas it picked up good, and if I let off it idled down no backfire or anything. but trying to hold a same speed down the highway with barely any throttle it would act stupid. timing?

 

[Big_John]

Could be running lean.

 

[66SportFury]

I was going to say timing. What do the plugs look like? Pictures? What ignition are you running? Electronic or points? Engine?

 

[bulldogchesty]

Sounds like a miss fire. Either a plug is bad or a plug wire is going to ground.

 

[commando1]

It's the certain spot on the carburetor itself.
Bring it to the same RPM and hold it while in the driveway and in neutral and it will do the same thing I bet.
If it does, concentrate on the carburetor first before moving to other stuff.

 

[70NPORT]

Edelbrock? I had one that had a dead spot like that a few years ago on another motor.

 

[saylor]

its all stock and cheapo replacement parts - 2 barrel rebuild carb from summit, stock plain ol distributor, 20 dollar universal plug wires, $1.25 champion plugs el cheapos. on a stock 383 2 barrel.

I haven't pulled the plugs to look at the end colors, not a bad idea. It didn't overheat, and it never starved for fuel, so I hope im past all that crap.

lean condition is possible, and so is timing. both were set by me - and I have 0 expertise. im a computer guy not a mechanic

 

[saylor]

at least the suspension is solid as a rock. I drove a road that I drive daily in my nitro - hit one of the same road bumps, the fury handled it WAY better than the 2010 nitro. I just giggled. then I thought what a piece of **** nitro I have.

 

[300rag]

... im a computer guy not a mechanic

So you fix new cars for a living??:glasses1:

 

[65sporty]

A ign miss should be a quick sharp jerk, a bog or surge is usually fuel. do a easy brake torque is driveway if it's ign it will miss.

 

[NewportTM]

I was having the same problems. Took the car in to a very reputable shop. They adjusted the floats on the carb, set timing properly and changed plugs (it was running lean). I do have pertronix installed. They made sure the gap on the pertronix was set properly. Now the car runs great. One thing I was told is that a bad timing chain can lead to problems like I was experiencing.

 

[moper]

Disconnect the vacuum advance at the distributor and plug it. Test drive it. Igf it doesn't studder then take an 11/32s allen wrench, stick it down into the distributor's vacuum can through the vacuum nipple, and engage the hex at the bottom of it. Then turn the wrench counterclockwise 2 turns, reconnect the advance hose, and drive it again. If it still does it, give it another 2 turns and test again. Sounds like it's got a hair too much vacuum advance. What you're doing is preloading the spring that the vacuum signal works against. It makes it need a slightly higher vacuum level before it reaches full advance.

 

[rexus31]

I was having the same problems. Took the car in to a very reputable shop. They adjusted the floats on the carb, set timing properly and changed plugs (it was running lean). I do have pertronix installed. They made sure the gap on the pertronix was set properly. Now the car runs great. One thing I was told is that a bad timing chain can lead to problems like I was experiencing.

Did you bypass the Ballast Resistor when the Pertronix was installed? Just curious.

 

[NewportTM]

Did you bypass the Ballast Resistor when the Pertronix was installed? Just curious.

The ballast resistor is still there, but it is not functional. What I did was remove the guts from it and then soldered a solid wire between the tabs. Works great and maintains the stock appearance.

 

[66SportFury]

If the car has points, I wouldn't recommend jumping the ballast resistor. It can lead to coil failure and point failure. But if it's electronic, then you don't need one.

 

[saylor]

I have not changed the points/condenser/other distributor parts - only changed the rotor cap and rotor when I did the plugs and wires.

I already have an oil drip at the dist o-ring.

I maybe will just buy a new distributor and new o-ring and change it up and see what I got.

 

[Hanover]

Start with the small free stuff. Timing. Check for vacuum leaks. Look at the plugs, are they sooty black or crystal white around the insulator of the centre electrode? Should be barely golden/brown. Rent a compression gauge for $5 and make sure you have consistent compression between all cylinders. After that you can get into tuning issues. Typically a misfire under light throttle would indicate a lean condition. You mentioned a rebuilt carb. Did you just bolt it on or did you mess with the idle circuit? I have no idea which carb you have right now but if it's a Carter you have the option of playing with metering rods at part throttle.

 

[saylor]

so - this is where I left of off last may when I went on hiatus

if the weather holds out tomorrow ill get out in the driveway and bang around and see what the plugs look like, etc.

 

[olmoparnut]

I had the exact problem on my 383 Road Runner after installing mopar electronic ignition. on a friend's advice I disconnected the vacuum advance. No more problem. car runs great during all types of driving.

 

[mcmlvii]

I had the exact problem on my 383 Road Runner after installing mopar electronic ignition. on a friend's advice I disconnected the vacuum advance. No more problem. car runs great during all types of driving.

Similar experience for me but opposite. I had a torn vacuum advance and the car ran great on just mechanical advance. I installed a replacement advance unit and now the car has the light-throttle hesitation/stumble....