'68 Chrysler T&C w/ Mystery Stutter

Greetings SW lovers. I need to consult with you on a perplexing runnability problem. When I purchased the wagon a few months ago it ran very smoothly except for an intermittent highway speed miss. It had basically been neglected for 10 years without any maintenance done other than oil changes. I then proceeded to do the following:
-plugs and wires
-coil
-fuel pump and filter
-valve covers gaskets
-air filter
-cap, rotor, points.
-set timing
-new brake booster and master cylinder
Then it ran much worse. The symptoms were rough running, missing or hesitation (expecially at a steady speed), sometimes a near stall. We have a great old school Mopar mechanic in town that has gone through it twice. He suggested that the carb base gasket might be it. I took it to another mechanic to replace the pinion seal and the carb gasket. He disassembled the carb and found some small pieces of a foreign spring in the throat. He also moved the timing of the accelerator pump and cleaned everything up. He replaced the gasket but it was fine. He reset the engine timing by ear.

Now it runs better but not good. The idle is still a little rough, there is still a steady speed occasional hesitation once the car gets hot. I'm thinking I'll pull the plug wires and check them again, and put the timing back to spec. What ideas do you have? It seems like it must be a vacuum leak or vapor lock? I've replaced the fuel filter twice.

Thanks, Ed
'68 T&C, 383 2bbl

 

I'd be looking all over for a vacuum leak. Sometimes you end up knocking something loose when working on it, or snapping an old brittle hose.

 

Don't rule out an internal vacuum leak in that new booster you installed.

 

Turbobill, I'm very interested in your comment about a possible vacuum leak in the brake booster. How could I detect that or identify it? Thanks

 

When you changed the fuel filter twice....was it clogged or real dirty?

 

A friend of mine who has a 68 Fury (also a C-body), had occasional stalling and after being towed home twice finally discovered a short rubber hose section under the car that is part of the fuel line that was dry rotted. Ocassionally the fuel pump would suck air through the cracked hose which visually appeared to be fine, and since no fuel was leaking out it took a wheil to pinpoint the problem. That may not be your problem, but it might be worth checking the fuel line hoses both up front and under the car.

 

Do the power brakes seem to work normally?

To test the booster or the line for leaks, find where the vacuum line going to the brake booster plugs into the engine (probably the intake manifold or the base of the carburetor). Unplug it, seal it with something and run the engine. Make sure the engine is warmed up and the choke is off. Does the idle improve?

If so, hook the vacuum line back up to the engine, then unplug the end at the booster. Cover or plug it, and idle the engine again. Is the idle still ok or has the roughness returned. If it has gotten rough, there is a leak in the line. If it smooths out, the leak is in the booster or at the rubber grommet where the line plugs into the booster.

There is another test to see if the booster is holding vacuum. Shut the engine off and apply the brakes five times. During the first two or three applications, you should hear a hissing sound from the booster as the stored vacuum is used to assist brake application. If you only hear the hissing sound on the first application but not the second, this indicateds there is a partial leak in the booster which will affect idle quality.

Based on the work you did to the engine, there are several other things you disturbed as well. Is the point gap set properly? Did you set the spark plug gaps according to specification? Contrary to what many believe, plugs do not come "pre gapped". Is the timing set properly? Does the vaccum advance unit work? Are there any other vacuum leaks? Any rubber vacuum hose is suspect on a 40 something year old car. Are the hoses or lines hard, brittle or are the ends cracked or hard where they attach to their nipples? Do they fit the nipples well or slide on and off easily? Is the firing order correct? I suggest you check and double check all your work and look very hard for vacuum leaks.

 

Also test booster: with car idling,, press on brake several times hard and quickly & listen to see if engine falters. A lean-carb will cause high rpm hesitation too!.

 

Station Wagon hesitation

Many months have passed since the last posting to this thread, but unfortunately not the "miss". In the intervening time, we have a new NOS carb, timing set, valve job. The car does run better but still has that miss. I could not reproduce any problems from the brake booster. I'm thinking I'll change the fuel pump again and check and clean the plugs. I've checked the wires multiple times. Ed

 

Maybe the distributer is bad? My 69 Monaco wagon never ran quite right untill I converted it to Mopar electronic ignition. after installing the new distributer it ran great. The whole kit from the dealer was about $250 but it runs and starts warm or cold so much better it's worth the money. Sounds like you covered everything else.

 

Distributor

I forgot to mention, I also replaced the old distributor with Mopar electronic ignition. No luck!

 

sounds like you might just have a valve thats carbon'd up.....you could try the old rev the heck out of it while squirting water down its throat !!!

I thought my father was nutz when he told me this 40 year ago
but ive done it a million times since with good results

....or you could do a leak down test on it...

 

Rev....see above.

 

All new valves. One cylinder was a little low, so went ahead and did the job. No effect on the hesitation. Ed

 

oooops...my bad...my speed reading aint what it used to be