my truck is smarter than i am lol

[midnite]

gota new riddle for ya'll. gave my truck a tune up and an oil change. it was in desperate need of both. i was out the other night just cruising around and outta the blue it started missing. so i pulled the new plugs and loooked them over to see if maybe something fouled them out. checked them for spark as well using the new wires. all 6 had spark and the appearance of all 6 plugs appeared normal. considering that they're about a week old. no oil,no corrosion,etc. so i decided to take it for a "spirited" drive just to see if it would help it any. while driving i noticed that when i "romp" on it the miss goes away and the truck runs as it should. but when i drive it "normally" it runs rough and also does so at idle. i have a repair manual for my 86 bronco 2 and i looked up possible causes for misfiring and it just says to check plugs,wires,cap,and rotor. it doesnt matter if the engine is cold or warm the miss is there but when i put my foot into it it runs perfectly no miss,clatter,tapping etc. any ideas?? im stumped here. as always any and all advice is greatly appreciated. truck has the 300 6 single bbl carb. and approx. 182k miles. thanks again for the tips. bill

 

[jebadiah04]

Did you gap your plugs?

I would suspect maybe a faulty plug wire.

Sent from my mudwhistle via lemmiwinks.

 

[jebadiah04]

Also...on a 300 you actually can get the plug wires in the wrong place and it runs semi-ok.

Sent from my mudwhistle via lemmiwinks.

 

[Wbruiser2]

Double check your vacuum lines. You could have knocked one off or broke/cracked one during your tune-up..

 

[dustybumpers]

Sounds like the carb may have loosened itself, creating a vacuum leak. When you apply throttle, the cable pulls it tight, stopping the leak.

My 82 did that too me once. Took forever to figure it out

 

[midnite]

thanks for the advice on the vac lines and the carb loosening up. i will look into that tomorrow. as for the vac lines i noticed that the vac advance line was unhooked i dont know if it was done by me or if it was like that when i bought the truck but i re-connected it and it seemed to help the problem a little bit but not too much the miss is still present but not as bad and disappears at a lower rpm now(around 2k rpm before the adv was hooked back up around 1500 or so now) so ill check the rest of the vac lines and carb tomorrow afternoon.