87 bronco II studering ?

[dch1992]

when i drive no matter what speed or if the motor is cold or warmed up the motor will randomly studder for about 1 min to 3 mins it will run horrible vacuum gots down to about 15 or lower exhaust sometimes puffs black smoke no throttle response until you have you foot down . once it clears up its fine and runs good ? any thoughts on what could be causing it ...

87 bronco II
2.9 v6

has new internal and external fuel pumps new fuel filter new plugs i have ran sea foam through the gas and brake booster no help

 

[BlackBII]

Black smoke = too much fuel.

Whats the fuel pressure at when its running?

How do the plugs look? Black?

Have you pulled the codes?

 

[dch1992]

the plug i just replaced that had about 300 plus miles on them were black i still need to pull the codes but its not showing any at the moment and as for the fuel psi im going to find that out tomaro hopefully

 

[master hec0]

issue similar to mine but mine sounds worse because it would actually stall if i let off the gas at a stop light. but what corrected mine was o2 sensor and it was an 87 also

 

[dch1992]

the o2 sensor would make sense i have a bad engine wiring harness the previous owner burnt some wires... conected the battery up backwards lol ill look into that thanks

 

[master hec0]

yeah i wired up my battery wrong i smelled smoke and had a few electrical issues resulting.
wires melted together and started burning the next time i tried starting it. and a looped plug melted and shorted out on the metal of the dashboard. if you get an intermittent no start check under your dash for a wire with a plug on the end of it with a looped piece of cable on the end of the plug. electrical tape is your friend.

 

[kimcrwbr1]

yea check all the sensors connectors wires vacuum lines if it dont look good it is possible it is not good. look at all the grounds take them apart clean them and put them back together (especially the coil ground) then take it to a parts store and have them pull the codes for you unless you can do that yourself. check fuel pressure, vacuum, compression, change oil, filters. Does it have a egr kinna sounds like a sticky egr valve or vacuum related with a faulty O2

 

[dch1992]

thanks everone who posted the o2 sensor was the problem the connector was laying on the y pipe and melted lol and then the black wire of the three waas chewed up close to the o2 sensor got it all fixed runs great now idles much better runs way smoother and has more power and a better smelling exhaust lol thanks again everyone

 

[kimcrwbr1]

cool thanks for the follow up cheers

 

[master hec0]

make sure to zip tie the wire up high so it wont melt on exhaust again. when i replaced mine it was sip tied obviously to prevent melting of wires i believe it was from the factory since we have had it since it had 20 000kms on it and i was the 1st to replace it.