78 country squire engine misfire

Those are what are called "positive pressure" valves, which require exhaust pressure to make the valve actuate. Install the valve, start the engine, then put a vacuum pump on the valve and slowly apply vac to begin opening the valve; the engine speed should begin to slow down in proportion to how much the valve opens. Open it enough, the engine will misfire, and eventually stall.

 

Aha!
I figured there was something I was not aware of.
Can I bench test the new valve before I install?
It's a pain to put it all back together and find I still have my misfire......not only to find another faulty valve.
Suggestions?
Thanks,
T

 

No. That's why I said you have to install it. But in installing it, it's another step to finding the misfire. That's why you do the test I recommended, to ensure the valve is working.

 

Okie dokie!
I'm on it..
Thanks for the information.
I would have kept sending these new valves back until I got tired and ripped all the emissions crap off!
Never been one for much patience..
T

 

Have you checked the condition of your plugs?
I recently had a miss on mine and found a fouled out plug.
Changed a plug wire and it seems to be ok now.
Does your car have catalytic converter?

 

Oh ya......
New plugs, wires, etc.
Yes, I do still have the cat's.
So........ Here's where I'm at.
I'm focusing on air/fuel not, having eliminated electrical.
Changed the EGR, sent the carburator out to "Datona Carburator" to have rebuilt/restored.... And.... Siphoned out the "ethanol" gas and replaced with non-ethanol.....
So far, so good! Idles smooth, revs up nicely and seems to run fine.
Taking it out for a test spin later today.
DANG! Thus crap Ethanol gas is killing me!
I never realized it was so bad.... It kills small engine carburators, eats up rubber fuel lines and causes our old gems to run like *%^#^#*^+!!!!!
Anyone else find this to be a problem? Or is this just a regional Florida thing?
T

 

I don't think it's the ethanol, per se; I think your carb had a problem. You should've waited until reinstalling and running the carb before draining the tank. That way, you would've conclusively known whether the carb or the gas was to blame. '74-and-up Fords with the IMCO (improved combustion) redesign were specifically made to run on 10% MBTE 87 Octane gasoline. I run ARCO unleaded in my Ranchero with no problems, and the engine is set up exactly the same as yours, except I don't run the EGR and Thermactor.

 

Also, when you siphoned the tank, did you look at it to see if there was any water in the fuel? Even just a few ounces in the float bowl will affect fuel feed in the carb jets.

 

Well, Andrew. You're probably right. I just didn't want to get tainted fuel in my fresh carb. Daytona Carb does one awesome restoration!
I didn't want to compromise that.
Anyway, I'm sticking with non-ethanol from now on.
Btw. Tell me more about the EGR and thermactor. It looks like bypassing the EGR is simply blocking off the manifold, but what is the thermactor, where is it and what does it do?
T

 

Thermactor is the air injection system...injects air into the cat as well as upstream in the exhaust passages to "after burn" leftover hydrocarbons in the exhaust stream. As for the EGR, just disconnect the vacuum to the valve itself, plug the vacuum line (I use golf tees for line plugs) and it'll be out of commission.

 

ARGH!!!!
I took it out for a test drive yesterday. It ran sweeeeet! Idled smoothly. Nice mid range and flawless on the freeway.
I ran about fifteen miles, pulled off the off ramp and bam! Crappy idle, missing and running rough!
Actually felt like two plug wires off. Checked all that and everything is tight. No crossed wires. All looked good.
Let it cool down. Started back up and same rough idle and doesn't go away when I drive it.
I've never experienced this kind of a problem with any car I've owned.
I hope someone out there has and can point me in the right direction.
Please don't tell me about crossed plug wires, fouled plugs, water in the carburator, etc.
this is like the third time I've gone through this. I am going to replace the distributor with a pertonix flamethrower and the coil.
I just don't understand why it will run sweet after I work on it. Only to fall on its lips when I drive it...
Stumped!
T

 

Vacuum leak. Or the coil, as you suspect.
Seriously consider the Duraspark ignition system.
It is really good and designed for a Ford.

 

Probably not helpful at this point, but I'll chime in again to repeat my suspicions of a vacuum leak SOMEWHERE. If I recall my situation accurately from a few years ago, my mechanic found my leak at the brake booster. Once that was replaced, it was smooth sailing. I know the frustration you're feeling and wish you the best of luck!

 

x 3 on egr spacer major problem with these years .Just omitted one on a 74 400 with same symptom. If you haven't removed it to examine you need to. They also use a special gasket between spacer and intake.

 

All salient points, and now with your test drive, it points to a vacuum leak. When an engine's enriched on cold or ambient temp start-up, the extra fuel masks the vacuum leak; once the choke butterfly opens, the mixture leans out and the engine runs s#!tty. So, take a can of carb cleaner and lightly spray the intake gaskets, the carb spacer top and bottom, the EGR valve passages behind the valve, and then use a pair of needle nose pliers to pinch off each of the vacuum lines. Do these first and if you have any questions, do not hesitate to 'start a conversation' (PM me) and I'll do my best to answer.