1982 Straight 6 300 - had been sitting a couple years. Idles rough, sounds rough, coughing light blue smoke. Changed oil, filter, plugs, fuel pump, pcv valve. What should I do next ? Thanks

 

Rebuild carburetor

 

Post in the engine area under the 240 / 300 six
OR
80 - 86 truck area as you posted in the 87> and people may not know it has a carb and maybe a feed back system. I cant see the carb or dist. to tell if it is or not a feed back system.
Do you have a vacuum line going to the dist.? If so not a feed back system.
Feed back system you say? Yes a rude computer controls the carb settings and a few other things so if the computer is getting bad information that could make it run bad.
Any sensor that is bad will give bad info to the computer and make it go into "limp home mode" and run bad.
BTW some of them sensors you cant get any more so could be SOL on having the feed back system work right but there is a fix if you don't need to pass smog test / look over.
Change the carb & dist. back to DSII non-feed back system (80-81). So being a computer first thing to do is pull codes to see what it has to tell.

I take it you have drained ALL the old gas out of the tank(s) and maybe cleaned the tank out or at least checked for rust & junk?
Bad gas can make it run bad.
Check ALL vacuum lines for cracks and replace as needed. There is a vacuum tree down low and to the rear on the intake manifold that has some hard to see ports with caps that crack and fall off.

On the smoke how many miles on the motor, what is the track record for oil changes & tune ups?
Have you done a compression test or leak down test to see what shape the motor is in?
When you change the oil don't use that "orange can of death!" They go bad on the inside and cut back oil psi and that is not a good thing.
You cant see this with a oil light only a after market gauge. I will never run one again after seeing it happen on my own 02 Durango. The 10 min oil change place uses them I have not been back since.

I should have looked over the video first, do a compression test, a dead hole will never get it to run right.
If compression is good then maybe a tune up is in order? Plugs, wires, cap & rotor to start.
It sounds like you have an exh. leak would that be at the manifolds & head? If so a leaking intake gasket can make it run ruff.
I gave you some things to check good luck
Dave ----

 

Thanks for the suggestions. Not sure if it is a feedback system. Will check

 

Here is pic of distributor

 

You are safe as it is NOT a feed back system as it has the vacuum hose going to the dist. and as a guess the carb would NOT be feed back also
Think late 82 is when they went with the feed back system.

Did you drain the old gas or did you put fresh gas on top of bad gas in the tank?
I would do a compression test to make sure you dont have a dead hole.

My 81 300 had a miss when I first bought it. the first thing I did was a compression test.
All holes where good, installed new plugs, wires, cap & rotor and the miss was gone.
If it was a dead hole I may not be driving the truck today.
Dave ----

 

Ok i will do compression test next. Thanks for your guidance my friend.

 

If compression is good, would you do distributor also or just cap rotor and wires?

 

Just cap rotor and wires only because if the truck is new to me / you I don't know when they were last changed and I would then know they "should" be good.
I say "should" because with todays new parts some are bad right out of the box.

Maybe before you do the compression test with the motor running pull 1 plug wire off at a time and see if that makes a change in how the motor runs.
If that hole in doing its job when the plug wire is removed the RPM should change and motor run a little ruff.
If the hole is not working or working hard there will be no change or vary little change in RPM.
Then when you do the compression test you can look a little closer at the hole that did not change RPM.

Another tool you can use to see if a hole is working. Cold motor spray a little water on the exh. manifold at the head so they are wet.
Start the motor and let run only a little bit and shut it down. Now look at the exh. manifold, if that hole was firing it would of heated the manifold and the water would evaporated off and not be wet on the hole(s).
Just tools to use to find where the issue could be.
Dave ----

 

Thanks Dave. One other question for now. How can I tell which carburetor I have? I looked all around it and I don’t see any tag on it. Only thing I see is “Carter for Motorcraft made in america” and “2624”

 

check your vacuum lines, not cracked, missing

circled,
is that capped off, or with running, cap off if you feel vacuum.

 

Ok fuzzface here is result of compression test. On the one that is 110 I poured a little oil in spark plug hole but there was no change in
pressure. Would any of these readings lead to the rough running, low idle, and black smoke from exhaust ? If no, what should I do next? Replace carb? I don’t know how/where to test to see if a vacuum problem. helllllllp!

 

[QUOTE=torq'ta 5 8;19412173]check your vacuum lines, not cracked, missing

circled,
is that capped off, or with running, cap off if you feel vacuum.[/QUOTE

That is capped off