I did something really dumb. I went 4 wheeling in a very dusty enviroment and completely forgot about checking my air filter. I somehow managed to get dirt and dust all inside my carb. Well the bronco ran fine the day i went four wheeling and the day after, but when i cranked it up today, it barely ran. i have to give it gas just so it won't knock off and it smokes out of the tailpipes. i took the plugs out and inspected them. they indicate that the engine is running rich. this is a fairly new 351HO engine with very few miles on it so i know its not worn out. i sprayed some carb cleaner down the carb figuring it would help some and it did... but not much. A friend told me that my cat's are clogged up... do you think that's whats wrong? This is my daily driver and its not in driving condition the way it is now so any help at all is very appreciated.



1985 Bronco XLT, 351HO 4bbl, C6, NP208 ,9" 3.55 limited slip, Warn Premium Hubs, Quad Front Shocks, Dual Flowmaster 50's, BFG 32x11.5 ATko's

 

This might seem wierd buuuttt take some WD-40 and spary the inside of the cap and distributor (man I hate spelling that word) down. Get nice and clean in there then fire her (or him for those that are pol-lit-ic-ally correct) and see if that helps.

 

I checked the distributor cap and rotor and they seem to be fine. I'm suspecting that it might be the power valve. First of all, does the motorcraft 4bbl even have a 'power valve', and if so, where is it located?

1985 Bronco XLT, 351HO 4bbl, C6, NP208 ,9" 3.55 limited slip, Warn Premium Hubs, Quad Front Shocks, Dual Flowmaster 50's, BFG 32x11.5 ATko's

 

You looked at the cap but did you clean it, and the distributor, with WD-40? I don't want to get into a big long thread about eletrical theory, statical charges, proton exchange, and dust but to say; ever notice the first thing in your house to collect dirt is the tv set? Ever notice that a dirty TV screen doesn't have an static charge but a clean one does? Or is that they other way around .....hummmmm

Ok the power vavle in the carb is located in the front fuel bowl. Remove the four screws holding the bowl on and it's the big thing right in the middle of the metering block on the carb. To find out if it works take it out and (hope you like the taste) suck on the open end. The spring loaded plunger on the other side should move in and out.

Normally the only way to burst a valve is to have backfired through the carb. If it's damaged you can get a new one for around 5 bucks. Besure you get the same rating as the valve you removed. To find the rating look on the valve for numbers like 10.5 11 11.5 and so on. The number of the valve is the pounds in vacuum needed to open the valve. To pervent blowing a valve there is a little kit that includes a check ball and spring that is installed in the bottom of the carb. The kit is around 10 bucks at most auto parts stores.

Usually a bad valve wont be enough for your engine to smoke out the back, but it could happen if the vavle had a huge tear in it.

I grew on a farm where the drive way was one and a half miles long. It wasn't uncommon at all to have dsut build up inside a cap and distributor and stop the truck. That's why I suggested cleaning the cap and distributor with WD-40

 

If its black smoke look down the carb when its running and see if fuel is dripping out of the venturi's. The needle and seats may be sticking.

 

those tips were great heres a few quik easy ones too
since yuo were muddin, you might check your air filter for being extremly clogged, also is your choke working right?

with the black smoke it deffinately getting more feul than oxygen (or
spark)

good luck
keep us posted

 

it appear i didn't read your post as closely as i thought i had
sorry
i do hope it all works out