I wonder if the knock sensor is picking up ping and dumping fuel on just that bank. I don't even know if that's possible or not. I know normally the ECU will pull timing when the knock sensor detects ping. Have you compared #1 to another cyl on the same bank (side)? What side is #3, same or other?

 

Yah i compared it with other cyls to see if it was right when it was not acting up. And i picked certain rpms, tps position.. in OD.. etc.. and they all seemed to be about the same voltage. I could't check them at the same time though and i don't think it was ever acting up when i had it on other cyls. So... mmmm.. now you got me wondering again.
Guess i could borrow another multi meter and check a couple cyls at the same time. But the other cyls have not showed any signs of being way rich. plugs are always clean when i check them.

Yah i don't know on the knock sensor, i always thought they just pulled timing out.
Everyonce in a while if i let it load up long enough.. the truck goes from a shudder.. to a full blow jerking but only for a second. Then it stops. I figure that may be the knock sensor kicking in when that cyl gets so loaded up it can't run anymore.

I just can't think of anyway how somthing else being wrong would only cause this to happen on one cyl.
but that being said.. i guess i wouldn't exactly be blown away if i put this used ecm in and it does the same thing. I suppose there is always somthing else...

I'm burnt out on working on this outside in the cold anyway.. so i'll enjoy my break from it and hope the ecm is it i guess. If its not... wow.. i wouldn't know where else to begin then. At least i know what its doing now!

 

glad to see you are making some progress.

i would test the other injectors in that bank just to compare. though I'm leaning towards the ecm being at fault, they usually dont go bad but with the voltage climbing erratically like that make me wonder.

keep us posted!

 

All three injectors on that bank were the same ohm(within .1 volt) of each other both cold and warm.
Plus i swapped the #1 and #3 injectors around and the problem did not move to the #3 cyl. So i figure if it was an injector the #3 cyl would be acting up now.

The ECM shipped out today(us mail) and he is only 1 state away so i'd think i'd get it pretty quick.

REALLY hope that it. Just don't see what else it could be.. but you know how that goes!!

 

Its FIXED!!!

Well i got the used ecm. And to my not so much surprise.. it did not fix the problem. mmmmm.....

I had tested continuity of that wire before.. but at the time didn't realize how the injectors fired(pulsing the negative wire). So i thought maybe in that original 3.4 harness there is a place where its feeding off another ground.. or rubbing on metal and getting a false ground... etc...

I ran a jumper wire direct from the injector to the ecm. Its been 164 miles and so far not a single hicup! smooth. so i think that was it.

I'll be driving 230 miles tommorrow and will give it a good one day test. That will be enough mileage to really tell me if that was it. I can't rember the last time it ran this long without stuttering so i think we are good.

Wish i would have thought of that before i bought the used ecu... but oh well.
Anybody need at T-100 4x4 auto ecm?

Thanks everyone for the postings and brainstorming. I always like figuring out things for myself.. but this is one i was about ready to give up on!

 

Very interesting, hope you got it! Good work BTW.