: 1970 coupe sputtering when hot



marcscaddy75
05-01-11, 10:04 PM
hello, hope someone can help me out? when i start my car it runs perfrect! once the engine gets warm (both at idle or driving) it starts sputtering out and die. i can start back up right away but runs very rough and backfires. any ideas????

77CDV
05-01-11, 10:24 PM
Sounds like a carb problem, or perhaps the choke or throttle linkage.

csbuckn
05-02-11, 11:26 AM
I think its the choke plate also, especially if the only thing it does good is idle.

marcscaddy75
05-03-11, 12:27 AM
i can drive the car also and it runs great even under heavy load and full throttle, but it seems that when the car gets to a certain temperature it starts sputtering and dies out

csbuckn
05-03-11, 12:36 AM
Like 10/20 minutes after driving does it happen? Still seems carb related. When it starts acting up, look at your carb and see if the choke is open.

cadillac_al
05-03-11, 09:42 AM
I think the fuel pump is dying or the coil is dying. When it dies, pop the hood, take the top off the air cleaner and look down the carb and pump the throttle. If the gas squirts out nicely then you have fuel. If it barely dribbles out you are starving for fuel. The only time I ever had a coil act up and run bad was on my 70 Deville. This is because if you ever leave the key on and the points happen to be open, your coil is frying. It took me a long time to figure out that coil issue because it was a new chrome one and I always thought when they died they died. This was the only one I ever had that would run half ass. I burned up the first one by leaving the key on once.

marcscaddy75
05-06-11, 01:38 AM
did you find it was the coil only when the car warmed up? my car runs perfectly until it warms up. also there is a new fuel pump and i also have an in line fuel pressure gauge so i know im getting fuel.

cadillac_al
05-06-11, 08:05 AM
It seems like mine didn't run perfectly with the bad coil but it got much worse after a couple minutes. It sounds like you can almost rule out the fuel issue. You have pressure to the gauge; it could still be clogged at the carb inlet filter or something wrong with the float. I would think those issues would make it run bad when it's cold too so it's looking more like a spark issue. I used to change points about every year when I had those old cars. If I tried to get more than a year out of them it just wouldn't run right. That's why I convert everything to HEI nowadays. I would have to say your problem is either with the coil or just the points and condenser. They are all pretty cheap.

marcscaddy75
05-06-11, 09:30 AM
thanks, i just changed the distributor back to all new factory original. i had bought a petronics ignitor but it didnt work right (i dont think it was gapped correctly) and car ran rocky with slight skip. once back to original spec it runs great till the cut out. im going to replace coil, even though this will be the third coil in a year, i cant figure anything else out. Do you think if the timing is off by 1 or 2 degrees that it can cause my particular symptoms? Thanks again

cadillac_al
05-06-11, 08:10 PM
1 or 2 degrees of timing won't make that much of a difference. If you have too much you will probably know it because it will be hard to turn over when it's hot. A lot of people love their Pertronix systems. You might want to keep it around if you start having issues with the points later on down the road. By the way, did you ever verify that the choke is opening all the way?

Sponson
05-07-11, 10:36 PM
What ignition wires do you have? If you have copper core wires and are using the pertronix, you will have it will start missing, backfiring, sputtering, really bad. Use silicon core wires with the pertronix and your problems will go away.