304 engine miss following tune up & exhaust re-route
I have a 79 CJ5 with the 304. I had the vehicle running very well following a rebuilt MC2100 Carb install and a new coil.
It had side pipes that were loud and I didn't like the constant exhaust smell.
I had a mechanic run the pipe out the back via a custom exhaust using a “y” pipe run into a single muffler, very much like the stock configuration.
It sounds perfect. However, the vehicle has developed a pretty significant miss. I had the mechanic then replace both fuel filters, put new plugs in, spark plug wires, distributor cap and cap button. The engine feels really crisp now but has a miss. It idles as if it has an oversized cam shaft.
I have re-routed the vacuum lines to the distributor from the carb vs the intake manifold and this did nothing.
I am still getting pretty strong fumes and the inside of the carb is very wet around the barrels when I look inside. The choke is fully opened and no issue with it being stuck closed … it is actually stuck in the wide open (no choke) position.
What could have happened with the new exhaust and potential added back pressure?
I used to be able to run along at really low RPMs and it was smooth. Now, it just chugs. It actually runs best a full throttle.
The baffling part is why it ran so well previously and now with exhaust reconfiguration, it is running rough.
Another mechanic suggested possibly a stuck valve. I have not performed a compression check but am still questioning why it would have gone from running well to a miss like it has.
Thanks in advance for any tips! It feels like I am on my own to figure this out.