BroncoII4x4.com

well ive been having this poblem for about a week now.it started one day without waning and is intermittent. but EXTREMELY frustrating!

my 87bii 2.9l 5speed 4x4 started backfiring through the intake. and while you are drvng, and are on the accelerator, it randomly shuts out, not giving any gas or power. it does this in random gears.. some gears run great and the others are having the problem.
and other times it is really bad. backfiring constantly and my TOP speed is anywhere beween 15 and 35 mph.
rebuilt the motor last june
oil change and tune up about 800 miles ago
i checked my injectors=good
changed fuel filter=good
i have propper fuel pressure
i checked and cleaned my distrubuter=all good
checked plugs/wires=good
and my air filter is brand new, and clean
everything is plugged in where it is supposed to be on the motor.
i checked my timing, it was a little off, i set it at 12 like the book says, and when i put the ground back on, it went to around 30. sounded good and ran like it used to. but on the way home, thr problem started again. an it has kept doing it.. threw some stp injector cleaner in to see if that helps any.

any one have any ideas? im getting more lost/frustrated as time goes on.

thanks, kolton

Maybe the catalytic converter is clogged up.

i wish it was that simple. but i dont have a cat on my truck.

is the check engine light on? have you checked engine codes?
do you have anyway to know if the fuel/air mixture is correct or even reasonable? can you make the problem happen while idling so you can smell exhaust? with top speed less than 35 gas mileage might not tell anything. if you have a multimeter test the tps for min and max resistance and make sure it changes smoothly through the range.
http://autorepair.about.com/library/pic ... 057lib.htm gives the values.
check the ground on the oxygen sensor it should be on the block near the exhaust manifold.
can you watch the fuel pressure while you are driving and see if it changes when the problem happens.
try removing the iac and spraying it out with carb cleaner.

backfire thru intake.... sounds like cracked rotor or cap, just throwing this at you.

or coil going out

thanks guys, yeah i had checked most of that. coil looked like a culprit.

but the pin on the dizzy shaft had sheared itself so the gear was spinning freely when it wanted to...

all better now :)

what is a dizzy shaft?? never heard that terminoligy Tweeked my curiosity should a trivia buff would have me. thanks Ford man 45yrs

zookeyknee wrote:what is a dizzy shaft?? never heard that terminoligy Tweeked my curiosity should a trivia buff would have me. thanks Ford man 45yrs

"Dizzy Shaft" is the redneck technical word that means distributor shaft. The pin he is referencing just happens to be the steel pin that is drilled crosswise through the shaft to secure the "Dizzy Gear" also known as distributor drive gear. (Doesn't dizzy gear just sound sexy as hell.)

In some circles and areas a lot of slang is used . Dizzy being short for Distributor. It is actually way easier and much quicker to just say Dizzy instead of the technical word Distributor.

Class is now dismissed!!!

the dizzy shaft runs off the lump shaft. i may be a redneck