I have a 71 350ci/270hp with an automatic transmission that has been running great up until recently. I've started to notice when i stop at a light with the engine idling it seems to sorta pause or stutter every 4 or 5 seconds. I'm not exactly sure how to describe it but it seems like a sparkplug may be firing at the wrong time or something like that, it sends a tiny shiver throughout the car when it does it. I'm wondering some possible causes of this problem might be and how i could go about fixing them. thanks.

 

Check your spark pkug wires are not shorting out on exhaust take a look at the motor in the dark and you will see a light show if one is

 

check vacuum hoses and make sure egr valve is opening and closing properly...if that is stuck open it will run really bad at idle.

 

Try this, when you get home and it starts doing it again, take a timing light and put it on each plug wire and look at the light pulses to try to isloate which plug is causing the problem. Found my brother's miss this way, wound up being a hairline crack in the spark plug ceramic of his new plugs.

If you found nothing then I would start looking for a vacuum leak.


Good luck.

 

Try this, when you get home and it starts doing it again, take a timing light and put it on each plug wire and look at the light pulses to try to isloate which plug is causing the problem. Found my brother's miss this way, wound up being a hairline crack in the spark plug ceramic of his new plugs.

If you found nothing then I would start looking for a vacuum leak. When was the last time the carb was rebuilt?


Good luck.

 

I shoulda mentioned that I'm only 17 and when i got my vette two months ago all i really knew was that i loved the styling of the car and the V8 it had under the hood. I don't have a timing light or know enough about the vacuum system to check the erg valve, but I did check to see if the plug wires were shorting on the exhaust and they aren't. I also have no idea when the carb was last rebuilt or if it ever was but i took off the air filter apparatus and the carb doesnt look that dirty or old so i guess it was rebuilt sometime recently. The guy i bought it from said the vacuum system was redone four years ago. Thanks for the replies.

 

I like that idea for future reference...will the timing light not light if the plug doesn't fire?

 

That the idea. Either the plug or wire or cap will most of the time cause an unsteady light pulse along with a miss. It doesn't pin point 100%, but it will point you in the right direction. It's always worked for me with all cars with plugs and wires. This also assumes everything else is properly working properly and the engine is properly grounded to the frame.

 

when the car is cold and right after its started feel the exhaust manifold and if you have a cold spot on the exhaust manifold next to a cylinder compared to the rest of the manifolds that is the problem area

 

I still have this problem and its gotten worse, i checked the plugs and they seemed fine. Last night i was driving and when i would accelerate from a light it would lag and seem like it wasnt getting any fuel or something. Then later that night i was sitting at a light and it was really missing or stuttering then it just died. This morning i tried to start it and it seemed like it didnt want to start. I would push in the pedal and it seemed like it wasnt getting gas or something.

 

I really can't help answer your question, but I wanted to suggest that you pick up a shop manual for your year. The book is absolutely loaded with troubleshooting and other info on ever part of your car. Even if you don't plan on doing much work yourself, it's still good to have.

I picked one up (along with an assembly manual) when I bought my 81, and both have been indispensible. Good luck!!

 

how do you know fuel is getting to the carb? could you have a blocked fuel filter? try this ...spray engine starter spray down the carb and start the car , if it starts and runs and then dies by itself you know its a fuel starvation problem. look at fuel filter first and fuel pump second, other things could include a float stuck closed or a blocked fuel line.

pick up a Haynes manual at the local auto shop for about $22

 

Start with the simple cheap things first, then move up the list. It sounds like a fuel filter, so replace that first. If the problem goes away, great! If not, go to the next thing on your list and so on.

 

However if you know little/nothing about the car and have no reference material, these semi-detailed instructions may help. These are based on a Q-Jet Carb.

The fuel filter is located inside the carb where the fuel line goes into it. (assuming Bubba hasn't added an inline filter) Unscrew the fuel line from the carb, taking care to wrap a rag around/under it to catch any gas that will dribble out. Then unscrew the hex shaped portion of the carb body/housing that the fuel line went into. Don't lose the thin gasket/o-ring/washer on the carb housing threads. The fuel filter is inside this area of the carb. If the filter is crudded up or even if it looks OK, replace it. They can look fine and be totally plugged. These filters are cheap and easily found at most any parts store. Be careful when putting the housing back in place not to crossthread it and don't overtighten it as it can strip if you lean on it too hard. Then replace the fuel line and check everything, twice, for gas leaks after you start the car.

And BTW, don't be tempted to just leave the filter out as you will shortly have an even bigger issue w/o it when the carb starts getting crude in it.

Hope this helps. Let us know how you make out.

And Good Luck!

 

Is there any possible way it could be my torque converter b/c it does not do this when my car is in neutral, just in drive while stopped.

 

If it only has the problem with the engine under a load, I would lean towards the ignition system as the source of the problem. A set of plugs is pretty darn cheap, and running the car at night with the hood up and looking for arcing plug wires is free. Take a look at the cap and rotor and check the condition of the points as well.
Good luck!