[mcarbaja]

I have a 64 pontiac 389. The car has 3 problems. I am wondering what it might be so that i can solve this problem. The car has a petronics ignitor instead or points, MSD 6 and regular AC spark plugs i have ACCEL disturbutor cap and rotor . When the i drive the car it drive and respons good. But sometimes it feels like if the engines skiped a beat. Sometimes it just , like turns off then turns back on . when ever it starts to have problems i look at the rpm gauge it goes to zero then jumps back up to more or less were it supposed to be . nothing turnes off in the car everything is on while this happenes. sometimes it happenes and sometime no. I checked the connection and evrything is good. I feel that the ignition is turning off but wonder what can it be . The car also sometimes pings like crazy right after it changes gears , i guess when it is giving straight power. that also happenes sometimes. At idle sometimes i will see the rpm move down a little like if it is misfirring and sometime it will turn off but rare . I checked the cap plugs and wire and it looks good. any help will defently help me a lot

[mcarbaja]

I have a 64 pontiac 389. The car has 3 problems. I am wondering what it might be so that i can solve this problem. The car has a petronics ignitor instead or points, MSD 6 and regular AC spark plugs i have ACCEL disturbutor cap and rotor . When the i drive the car it drive and respons good. But sometimes it feels like if the engines skiped a beat. Sometimes it just , like turns off then turns back on . when ever it starts to have problems i look at the rpm gauge it goes to zero then jumps back up to more or less were it supposed to be . nothing turnes off in the car everything is on while this happenes. sometimes it happenes and sometime no. I checked the connection and evrything is good. I feel that the ignition is turning off but wonder what can it be . The car also sometimes pings like crazy right after it changes gears , i guess when it is giving straight power. that also happenes sometimes. At idle sometimes i will see the rpm move down a little like if it is misfirring and sometime it will turn off but rare . I checked the cap plugs and wire and it looks good. any help will defently help me a lot

[Goatman]

Replace the fuel pump and filter.

[Ed Neasham]

OK, educate me. How will the fuel pump and filter cause the tach to go to zero with the engine turning? The tach recieves pulses from the distributor to calculate the rpm. If the indicated rpm momentarily goes to zero, that means that either the tach quit working for a short time or it quit getting those pulses for that short time, and therefore was nothing to indicate. When the pulses come back, it starts calculating again. Because the engine appears to "stumble" the same time the tach drops off, it appears to be ignition to me.

Ed

[ March 20, 2002: Message edited by: Ed Neasham ]</p>

[455HOGT37]

Might be the tach. I shut off my Bird at a gas station and it would not start again. I changed everything under the hood in the parking lot. My wife came to rescue me in her Bird and I robbed the whole ignition from her car, distributor and all - still nothing.
Last thing I tried was removing the tach wire from the coil. That worked.

[mcarbaja]

Its not going to be the tach because it was happenening before i got it, i got it to see if i would see anything weird and yes i did it makes me feel that its something else in the ignition that is stopping the ignition from working i feel it might be the petronics that why i have been thinking of putting back the point. Its defenetly not going to be the gas.

[6567GTO]

I have a similar phenomenon happening in my 65 which has a Mallory Unilite and a MSD 6A. Under acceleration it has sort of a hiccup which happens every now and then. It started to happen a little more frequently just before taking it off the road for the winter. I'm not sure what's causing it.

[Goatman]

Ed, as I'm sure you know, engines need spark and fuel to run. If Mig says his elctrical is "OK", then its his fuel.

When my mechanical went on my 70' GTO, it did alot of weird things. It would run fine sometimes, then it wouldn't start. Sometimes it would run only when I didn't give it gas (idle) or when I pulled the manual choke out. I once drove the car 15 miles down the highway at night with the car only runnning on the manual choke. Not fun, as you can imagine. Mechanical pumps will go slowly sometimes and their strange habits can make it hard to trace accurately.

[ March 20, 2002: Message edited by: Goatman ]</p>

[mcarbaja]

yes 6567GTO your their more or less were their and ed also whith stumble it feels like that its crazy.Goatman i feel that it actualy is electrical. We have that good engine only needs air gas and electricity. if the RPM metter goes to 0 in the spit secound then back up it makes me feel that it electrical. I could on feel that it might be the petronics( it goes in place of the points it uses magnets that spin with the rotor) just what i think i will try to do something todayand post it up

[Goatman]

It may be that Mig, but I don't know why you wouldn't think that that split second stumble couldn't be the diaphram inside the pump failing or pumping air instead of fuel.

If all else fails.............

[cpetrice]

I once had a 78 lincoln town car. when driving,it would sometimes just stop completely (I mean the motor) the rest of the car,ie lights,power brakes,etc seemed to work fine,then a few seconds later it would "catch up" and continue on. on some occasions it would idle,while in gear,if I gave it gas,it would not move,would coast to a stop then died. It would restart fine,and go on for another 10-20 miles. I replaced tons of stuff on that car,distributor,carb,sylenoid. damned thing continued to happen. after about $300 in parts,I finally figured out that the fuel filter was getting clogged and would get just enough gas to idle,but when you put on the accelerator,it would do nothing,until enough gas got in to match where I had the pedel pushed too. So,when it started to act up,I would pull over,take out the handy flathead screwdriver,take off the fuel filter,clean it out,and continue on.

[Tom Vaught]

I need to jump in here. Goatman, got to agree
with you on this one for the following reasons:
I had a 79 mustang one time (wife's car). She and
I decided to go to Colorado for a vacation. One
of my "buddies" had borrowed one of my gas cans and later returned it full of gas. Cool, 5 more
gallons of gas for the trip. Fast forward to the
great plains on I-80 west of Lincoln. Car ran great and got great gas mileage for miles and miles. Fact is every tank it got better and better
mileage but every so often it would have a sharp
jerk and then the motor would continue on. I was
wondering what was going on. Then it died. 3/4
tank of gas! Hum! I pull the coil wire and we got spark. I work the gas lever on the carb and we have no fuel out the accelerator pump. I take the fuel line off at the carb (before the gas filter)
and still no fuel. Take off the line before the pump. With 3/4 tank of gas I should see fuel now!
NO Fuel. Dam*! I know what it is, the dam*ed tank
fuel sock. Fortunately, this gas tank was like a GTO and you could see the fuel sending unit and
retaining ring. Knock the ring off, gas all over
everything. Pull the sender out and pull the sock
off and blow through it. ONE PINHOLE BUBBLE of
air. Throw the sock as far as I humanly can and
put the fuel sender back in the tank. Crank the
engine until it starts and drive for the next
86,000 miles with no problems. Tom V.

[GTO Karl]

Check the ground wire inside the distributor. It goes from the breaker plate to the housing, using one of the vac. advance screws. Most all the old factory wires are brittle and are about ready to break. If it does, it could cause intermittent ignition problem you describe as the breaker plate moves with the vacuum advance and the ground could momentarily be lost while it rotates and moves around.

Also, what kind of coil are you using with your MSD. I had a coil go bad once, each time I made a hard right turn, it would cut out just as you describe. I searched all the wiring around the steering column for ages before I finally figured it out. The coil was dented, and when you went around a right hand turn, the windings would bump the dented case, finally wearing through the lacquer on the windings, and creating a short each time I made a turn.

Good luck

Karl

[TURBO80T/A ROB]

I would try what goatman I had the same with a 74 firebird dirty filter it couldn't hurt and would be easier and cheaper then changing a dist

[Ed Neasham]

I still maintain that if you are going down the highway at crusing speed and the tach goes to zero when the engine stumbles, either the engine has quit rotating or the tach is not getting an electrical pulse signal from the distributor. Yes fuel problems could stop the engine from rotating (as many of you have pointed out), but if the engine goes from 55 mph to dead stop and back to 55 in one or two seconds, I think that you would "notice" something more than a "stumble", even with an automatic. I'm still betting on ignition.

[Half-Inch Stud]

Key clue "the TACH dies"...cannot be ignored.

I've added a ground wire from the HEI case to the Block ground...to avoid intermittent grounding. Otherwise, the distributor clamp is the only respectable ground path yet the HEI draws significant current and will erode the gounds continuity in the presence of oil...which seems to get there.

Some folks keep the distributor clamp just tight enough to allow moving the distributor by hand for fine timing adjustment...I used to do that, but not anymore.

Suggest you add an independent groundwire from distributor case to Throttle bracket. Also, suggest that any/all Crimp wirelugs be soldered onto the wires.

MSD-6 is another clue...can you bypass that, or install a complete HEI for troubleshoot?

H.I. Stud

[gtoguy1967]

half inch as i recall my 67 came factory with a ground stap are you sugesting replacing this or just making sure there is one there. Don

[455HOGT37]

That tach going to zero clearly indicates a problem on the primary side of the coil, but the "pings like crazy" sounds like a temporary lean condition, and I am sure G-man picked up on that. There may be a bit of both going on here.

[Goatman]

I hate sorting out gremlins! LOL Easy solution, rip everything out and start over with new stuff. Too bad money doesn't grow on trees like it used to.

[JJake]

Check the wire that went to the points, now to the Petronics sender unit. They sometimes get pushed down and rub against the distributor shaft wearing off the insulation and will ground intermittently. They are easier to find when the ground is permanent, been there.