I have been trying to get my 78 a little more up to par. I have repaired a couple of leaks (power steering and oil pan) and now I am experiencing a little hesitation/jerking while driving and trying to maintain a constant speed. If I am traveling at say 55mph and accelerate, all is well. If I accelerate from 0, it can be a little sluggish. If I try to stay at 55, you can feel a little jerking going on. I changed out plugs and wires hoping that would help, but it didn't. I've done anything with carb or distributor or timing.

a) Should I replace the distributor anyway since I have no idea how long it has been in there and see if this fixes my problem? I have had the car for 1 1/2 years and haven't changed it. I haven't done one, but am willing to give it a try.

b) Is it time for a carb rebuild? Haven't done this either, but wouldn't mind giving it a go.

c) Is it a good likelihood that the timing chain needs to be replaced? Is this something a true novice can tackle?

d) All the above

"I am experiencing a little hesitation/jerking while driving and trying to maintain a constant speed."

Sounds like it's misfiring, which occurs when it's running a bit lean. There's a number of causes of misfiring but the more common ones include minor or small vacuum leaks from rotten or cracked hoses. Spend some time to go over the entire engine, feeling every vacuum hose you can find, especially the ends that plug into things. Pay particular attention to those around the carb because the gasoline and oil eats the rubber, softening and causing it to swell. Also pay attention to the two hard plastic tubings that provide vacuum to your A/C or heater controls, particularly where they go into the corrugated harness stuff. Cracks in those tubings are difficult to see but if you gently bend them by hand, a crack will usually be revealed. If you find a crack in those, you can repair it using small-diameter windshield washer hose. If you can't find hose small enough, you can use RTV to seal the loose-fitting hose onto the plastic tubing but you must be careful to put the RTV only on the cleaned plastic tubing, then push the washer hose over the tubing and DO NOT let the washer hose slip off or you'll get RTV inside the tubing. If you do, you'll have to cut off that section of the tubing and start over.

When you slowly open the throttle while in Park/Neutral, does it begin misfiring at higher rpm? If so, you may have EGR problems; try disconnecting and capping the vacuum hose to the EGR valve and see if the misfiring stops. If so, remove the EGR valve (being careful not to damage the gasket) and examine it. It'll have some soot on the pintle valve that sticks into the intake manifold but it shouldn't be coated with gobs of carbon. If it is, you can gently tap the pintle with a piece of wood or rubber mallet to dislodge the carbon. Look in the manifold for carbon; if you find a lot, the EGR passages inside the manifold are probably pretty-well clogged and will need cleaning out. The easiest way to get that done is to take the intake manifold to a shop and have it hot-tanked and thoroughly cleaned.

Do you have a timing light and know how to use it? If so, hook it up, then use a paper clip or piece of wire to short the two right-most terminals of the ALDL diagnostics connector under the dash to put the ECM into diagnostics mode. That will cause the ECM to not control the timing. Then start the engine and find the timing mark with the light. Observe how steady the mark is; now slowly open the throttle while watching the mark and it should remain very steady, not moving at all (because the ECM is in diagnostics mode). If you see the mark jumping or moving around more than a degree or two, the timing chain is probably stretched some but even so, under steady throttle, even a stretched chain won't cause really noticeable timing jumps. The timing light should flash steadily and regularly. You can move the timing light's cable to each of the plug wires in turn, looking for steady and rhythmic flashing; that will reveal a bad wire, plug, or even an arcing cap or rotor.

It's highly unlikely that your carb needs rebuilding unless it's totally covered with gunk and junk. Before doing that, you can try running a can of GM's Top Engine Cleaner (TEC) through the carb. This fantastic stuff comes in either spray or pour cans and is available from any GM parts dealer, usually located on the shelves right behind the counter. Follow the directions on the can. A word of caution: if your engine has a lot of gunk/junk in the combustion chambers, the stuff can dislodge enough that it might clog the catalytic converter. It's best to use the stuff when you intend to change the cat or even with the cat disconnected or bypassed. If your engine's already fairly clean, there'll be no problem like this. TEC will often restore engine performance that you've forgotten has gone away through the years :o)

SteveH

I'm going to step away from this, because he has touched on everything i was going to mention. 8) nice job :-D

"I'm going to step away from this, because he has touched on everything i was going to mention. nice job "

Gracie :o)

But it doesn't count if it doesn't help fix his problems ;o|

Wow, thanks a lot. I haven't had a chance to check things out yet, but I will hopefully later this week. I will post an update when I have something to report. Thanks again.

also check for vacuum leaks around the base of the carb. pull your pcv hose off and look for carbon build-up there. pull the pcv valve from the valve cover with it running and feel how much vacuum you have there. quadrajets are notorious for becoming plugged up there where the hose goes on the carb, especially if the motor has lots of miles on it or is primarily driven in town. easy to fix if this is what it is but you will have to pull the carb off. once removed, look on the bottom of the carb where the pcv hose attaches and look for carbon build-up there. there are two cavities there with what looks like some sort of nozzle inside them. clean all carbon out, and i will warn you it aint easy. soak and dig, scrape, etc. until it is all clean again. there are some small passages in those cavities that are the source for the vacuum that need to be open. part of the reason they get stopped up so easy is they are small. after installing the carb and NEW base gasket, i prefer the fat one like what came on it new[better heat isolation]. don't forget a new pcv valve. i have fixed many cars this way when others thought they needed to rebuild the carb or worst case thought the motor was wore smooth out. hope this helps.

I check for vacuum leaks and didn't find anything. I never checked the timing. I adjusted my carb and made sure that my plug wires were separated and not too close to the headers and it is running a bit better. When time permits, I will pull the carb to do a closer inspection. Thanks for your help.

Don't overlook your spark plugs. Everytime my plugs begin to die, the very first symptom is exactly what you describe. Another thing: When the spark plug wires begin to die, I get that same symptom. Plugs and wires are not that much money and it eliminates a couple of possibilities.

Okay, my baby is running rather well these days...that is, when I can afford to put gas in it. Since the engine is running well, I have been trying to identify the next steps.

I am going to replace the door weatherstrips and the window felts, but I am really considering making some changes to the rear end. Of course, I would like to have positraction, but I am not sure how much $$$ that would cost me...both for parts and possibly mechanical work if I can't do the work myself. What would that cost me? And, if too much for me, any suggestions on an upgrade for my current setup?

Wow, having 84Elky advise you is like having him there handing you the wrench and telling you what to do next!

Next best thing!!!

You should be able to have a reputable tranny shop or the equivalent install a posi unit for around $400. More if the seals need replacing.