well, as the title states... im having some backfiring through the throttle body at light throttle/low throttle situations.

before i start throwing parts at it, i want y'alls opinions, and feedback.

i am replacing the o2 sensors, as they were both throwing codes. i have since disconnected both of them, but the backfiring continues.

the motor also bogs way down to almost stalling point before doing so.

i know timing is spot on, i put it all together, and made sure it was. merc225hp(mark) also helped(through email) so i know its spot on.

i also get from time to time, crank sensor loss of signal, and cam sensor loss of signal. so i was thinking of replacing those. along with the tps, as its
condition is unknown(came off the 5.9 tb from jy)

so im kinda at a loss. the truck is about to get a bunch of new electrical parts, unlesss i can pin-point whats causing it.

thanks guys!

 

sadly, everything you named can cause it to backfire like that. i have had a similar prob on going for awhile now, but i think mine is narrowed down to the fuel sync that i need to have played with and set to the right spot for my addons. yours could be similar...

 

sync was set to +2 per hemifevers suggestion. but bounces from 0-3, sometimes 4. which doesnt reall make sense, it shouldnt bounce around, should it?

guess ill just replace parts...

crank, cam, tps sensors, coil(came off our jeep, unknown age), and o2 sensors.

 

the sync will bounce +/- 1 normally. from what im told. but its also supposed to be set and read with it at 1000 rpms to take some of the slack out of the chain so its more steady of a reading.

 

i have the snapon mt2500 scanner, so it does all that for me. just need to reach back, and adjust the dizzy.

 

Anyone else?

 

I doubt its the TPS, so dont spend money on that. Don't forget I have a new crank sensor you can try, also have a used complete dizzy with cam sensor. We'll talk next sunday.

 

ok, so i got a replacement pre cat o2 sensor, and its still popping through the throttle body at light throttle(only when coldish) i still am going to replace the crank, and cam sensors, as the crank sensor is older, and from my 318, and the cam sensor is unknown as its from the jy 360.

im hoping to get some of this resolved within the next 2 weeks, after i get new tank straps... damn rust!

 

have you checked the fuel pressure? i know you just replaced the fuel pump

 

to me - backfiring through the intake is a timing problem.
also - loss of cam position sensor is critical to timing.
also - fuel sync is a measurement based off cam position sensor.
also - its been running fine up until now, right?

-----drum roll... my brain says cam position sensor first. crank position if that doesn't fix it.