Rough Idle, 77 Nova

[uadmlj1]

Compression within limits. Drop test didn't show anything. Tried tweaking idle via RPM then vacuum. No improvement.

[DanD]

Sorry man I don’t have any answers for you other then starting all over again.
Plugs, wires, carb mixture adjustments, fuel pressure, engine mechanical or what ever emissions that maybe on the car like EGR valve; from here I don’t know what else to suggest other than take it in to someone that is familiar with some of the old school cars.
Again sorry and I wish I could get under the hood of your car because seeing it in person makes a big difference as to what maybe happing.
Yes things in 1977 were a lot less complicated with engine performance but they had their quirks that only hands on will answer. Back then we were still called mechanics that could adjust, readjust and change things to make it work, we were not technicians that are held to what the engineers and the computer programmers have set out for us to follow.
If you do take it in and don’t feel a lot of confidence in their diagnosis post back and all of us here would be more then happy to have another read and see if it’s something feasible?
Dan.

[oldtimer5520]

I agree with the suggestions DanD made plus I would also check the condition of the points in the distributor. Check for decolonization at the contacts or for pit marks. Replace the points and the condenser if you find these conditions. Make sure to set the points to the correct gap. If you can still find a tach and dwell meter, use it to set the points if not you can use a feeler gauge. If you replace or reset the point gap you must reset the base timing again. Remember to remove the vacuum line from the distributor and plug it to reset the timing.
I hope this is of some help.
Ron

[uadmlj1]

Thanks for all your help.

[idol]

Hello guys, I know I'm coming in on this conversation a bit late, but if I may offer another option for everyone to consider.

Please allow me to ask uadmlj1 a question. uadmlj1 how old is your ignition coil? See in days past, our cars had this very peculiar problem, seems that as the coil began to age they would begin to breakdown. A very obvious symptom of this (but very misleading to those who were unaware) was the feeling that the car was running out of gas. Our what later on is determined to be a power loss. On avareage, most mechanics would immediately diagnose the problem as a bad fuel filter. But of course a bad fuel filter had other more obvious and immediate symptoms.
In the case of the Ign Coil breaking down it would rear it's ugly head as the engine heated, or during long high speed operations, or extended idling. The problem in the past was that until the coil actually quit the problem would continue on and the mechanic was doing many troubleshooting repairs and one of those repairs was to look for vacumn leaks.
So please allow me to suggest you replace your Ign Coil and since they are cheap, also your ign condenser (if you have breaker points in your distributor). I'm willing to bet this will resolve your problem.
Let us know...Idol

[re-tired]

The dice have been rolled The peanut gallery awaits the outcome of the bet in breathless anticipation. ;D