car has a miss

[mdazzo]

My Corvette Photos


slight miss in gear
hello,my 1979 always has a slight stumble or miss when in gear at the lower
rpm,s.the higher rpm's the miss is gone and no more stumble.is this a timing issue or a carb adjustment issue...350 motor.auto trans.
-in the past year new carb,new intake gaskets,new egr,new wires plugs,ect.
car has 14,000 miles on it...i just dont know where to go at this point.
can someone get me on course and suggest a path to follow...the car drives
i can live with the slight miss on somedays,other days i wish it was not present....
thank you
matt
mastic,new york

 

[BlackNBlue95]

My Corvette Photos


slight miss in gear
hello,my 1979 always has a slight stumble or miss when in gear at the lower
rpm,s.the higher rpm's the miss is gone and no more stumble.is this a timing issue or a carb adjustment issue...350 motor.auto trans.
-in the past year new carb,new intake gaskets,new egr,new wires plugs,ect.
car has 14,000 miles on it...i just dont know where to go at this point.
can someone get me on course and suggest a path to follow...the car drives
i can live with the slight miss on somedays,other days i wish it was not present....
thank you
matt
mastic,new york

I do not work on many carbed cars myself, as I am younger and have grown up around fuel injection.. but thinking on the basics here are my ideas not sure if they will help or not, I doubt it's an ignition miss because usually you see them worse under load.

I am thinking it could be a vaccum leak because off idle your vacum drops so the effect of a leak really it much less aparant as teh rpms rise.. or possibly a carb adjustment, if this was my car I probably would do a check for vacuum leaks with propane or use a smoke machine, if nothing shows up, then maybe adjust the carb and see if the problem goes away.

How long has the problem been there? I assume it was running fine after the intake gaskets and the timing was set at that time as well I would imagine...

just a couple thoughts... maybe I'm wrong so someone please jump in...
-=Rick

 

[jdp6000]

A miss could be just about anything on a "carbed" car. Start with the usual tune up parts....I see you have replaced some. Did you replace the cap and rotor? How about the fuel filter??

To point in a specific direction more information is need. Exactly what does it do and when? Example...does your choke kick in on cold start? Does it idle smooth when cold? Does it do it in gear while stopped? What happens when you put it in neutral? Does it miss on light excelleration? Does it only do it when its hot? Do you notice a change with the headlights up or down? Can you cause a change by putting the headlights up or down??

Jim

 

[SLOVETTE]

Had a miss in my '81, until my mrs. caught me!

 

[Samauriwarrior]

otfl That is good!!!

 

[mdazzo]

A miss could be just about anything on a "carbed" car. Start with the usual tune up parts....I see you have replaced some. Did you replace the cap and rotor? How about the fuel filter??

To point in a specific direction more information is need. Exactly what does it do and when? Example...does your choke kick in on cold start? Does it idle smooth when cold? Does it do it in gear while stopped? What happens when you put it in neutral? Does it miss on light excelleration? Does it only do it when its hot? Do you notice a change with the headlights up or down? Can you cause a change by putting the headlights up or down??

Jim

jim:
the car runs perfect with out a miss when not in drive hot or cold..in fact the car will run perfect in drive without a miss when it is cold.as soon as the motor is at full temp the car will miss or a stumble when i pull off from a dead stop on light excelleration.the car has never died . once the car is moving the motor runs perfect.as far as the idle in gear it will bounce up and down slighly which i guess you can call in a slight rough idle when a full temp .when the car is in neutral is is perfect i can step on the pedal ...no miss or stumble.the choke does kick in on a cold start.the car is very hard to start
when it sits for a week.i have to pump the pedal.then she will kick over.i dont have an answer as far as the lights i will check this out.as far as parts yes all new plugs wires, cap and internals, new carb, installed a new intake gasket,new dewitt rad,rebuilt the tranny and a complete new rear.this slight miss just started.l did have the choke adjusted in the late winter the car only comes out in the spring and the summer anyway when i had the carb installed about a year ago they had the choke way to racey on startup.
I hope this additional information will help me....thanks jim

 

[mdazzo]

I do not work on many carbed cars myself, as I am younger and have grown up around fuel injection.. but thinking on the basics here are my ideas not sure if they will help or not, I doubt it's an ignition miss because usually you see them worse under load.

I am thinking it could be a vaccum leak because off idle your vacum drops so the effect of a leak really it much less aparant as teh rpms rise.. or possibly a carb adjustment, if this was my car I probably would do a check for vacuum leaks with propane or use a smoke machine, if nothing shows up, then maybe adjust the carb and see if the problem goes away.

How long has the problem been there? I assume it was running fine after the intake gaskets and the timing was set at that time as well I would imagine...

just a couple thoughts... maybe I'm wrong so someone please jump in...
-=Rick

i wanted to thank you for input.the car did run good after the gasket was installed...the carb did race on start ups .I did have it adjusted...just dont understand why i have this miss out of nowhere..the car is only driven on the weekends so not a lot of miles on the new parts...

 

[jdp6000]

I would try decarbonizing the intake with a good cleaner for starters. If that doesn't work...My guess is fuel delivery related...possibly a fuel filter. Worse case scenario would be the fuel pump. Do you have access to a fuel pressure guage?

Do you have a couple of ignition wires crossing over? Make sure they are routed properly.

Try a cleaner first...see if that makes a difference.

Jim

 

[zachh]

If you put regular gas in it, that could be your problem. Mine runs perfect,except the time I accidantly put a full tank of regular in it. Mine is a Premiumpig! Mine did almost the same thing when regular ws in it. Also, You could possibly have a foul;ed spark plug. Check the gaps and condition of the plugs.

zachh