87 bronco II running issues need help.

[master hec0]

I posted this in bronco II specific also but i think i will get more traffic here
so i have been workin on fixing this bronco for about 6 months now i am now stumped on what is causing my problems. anyways heres the deal it starts and runs just fine when cold once i drive it for 10-30 mins it starts to missfire i get black smoke and eventually it will stall. the engine gets worse the longer you drive it but if i let it cool down it would run just fine again. this is annoying.
so i just had the timing done and the distributor replaced out of a parts truck i had and that didnt fix my problem so i am definatly eliminating timing/tfi and distributor as my issue. i have replaced my coolant temp sensor my ignition coil my wires/spark plugs throttle position sensor the map sensor the throttle it self and the computer on the passenger side in front of the door
i am at a loss also my mecanic said that fuel was good too. any help would be good and no engine codes either.

 

[adsm08]

O2 Sensor. My 87 Ranger did something very similar. I pulled my hair out for months and spent $100s replacing a lot of the same things you did before one day a back-fire blew my int. pipe apart. was down there replacing it when i noticed my O2 had fallen apart. Replaced that, left the battery off for a while to clear the KAM and she runs like a dream aside from this slight transmission bearing issue I have now.

 

[master hec0]

yeah i just ordered a 02 sensor off ebay earlier today i was thinking what else can it be. is there more then 1 02 sensor on these broncos? i only know of the one directly before the cat. too bad when i pulled the cat off my parts bronco i broke the o2sensor.

 

[lil_Blue_Ford]

Just one o2 sensor by the cat. Newer vehicles have more (my '00 Ranger has three or four).

 

[adsm08]

anything pre-OBD II (95 and older) will only have one, 96 thru about 99 will have 3 (2 on inline engines) and 00 and up may have up to 4.
What I found worked for me while I was driving as to cycle the key quickly, it kicks it back to Open-loop for a few minutes and makes it ignore the O2 signal. Its not a good fix, but you can do it while you wait for the new one to show up.

 

[PONYTAIL]

I Had A Problem With My 88 Ranger That Sounds The Same. I Searched Until I Gave Up And Went To Ford. Turned Out To Be A Cracked Vac Line Toward Back Of Motor. Good Luck

 

[master hec0]

do you remember what it cost roughly to take it to ford? if this o2 sensor doesn't fix it and then i will throw in a catalytic converter after that i will give up and take it to ford

 

[lil_Blue_Ford]

do you remember what it cost roughly to take it to ford? if this o2 sensor doesn't fix it and then i will throw in a catalytic converter after that i will give up and take it to ford

Hope you have deep pockets to take it to Ford... They'll wack you with a diagnostic fee then work you over in shop labor.

 

[master hec0]

my pockets are shallow just curious what the cost roughly was

 

[adsm08]

I didn't take it to Ford, I am Ford. Factory trained and certified Specialist Technician. The cat won't help unless it happens to have collapsed/melted. if the 02 is ok I'd check the EGR vacuum lines next. make sure the green one is in 1 piece (the like to break right under the TB, if thats ok disconnect the green one from the control valve and see if it has vac at idle. if so, the valve is bad, costs about $25. other things to check are that the PCV is working properly including that the hose on it is braided line, otherwise it will collapse with the engine running and can also potentially cause your issue.

 

[master hec0]

I didn't take it to Ford, I am Ford. Factory trained and certified Specialist Technician. The cat won't help unless it happens to have collapsed/melted. if the 02 is ok I'd check the EGR vacuum lines next. make sure the green one is in 1 piece (the like to break right under the TB, if thats ok disconnect the green one from the control valve and see if it has vac at idle. if so, the valve is bad, costs about $25. other things to check are that the PCV is working properly including that the hose on it is braided line, otherwise it will collapse with the engine running and can also potentially cause your issue.

how do you check if the pcv is working?

 

[lil_Blue_Ford]

how do you check if the pcv is working?

Around here you can get a new one for $5-7, either from a parts store or wal-mart, I usually just replace 'em. When they're really bad, it'll spit oil out the tailpipe... had that happening to one of my trucks