Have not read the thread in a while. But, is all this injector stuff with the intention of trying to get rid of the original misfire? Because if it is, That's crazy. LOL

 

well It started with the misfire... I wanted to upgrade while replacing them since they were pretty rough...one injector wasnt even the right part # and the screens were plugged... Ironically the misfire didnt go away until I changed the oil and added the engine restore... I also removed a set of injectors I was testing and reinstalled the original ones at that same time so not sure what actually took care of it but funney the same cylinder would misfire with two different sets of injectors and then run fine after those originals had the screens cleaned and reinstalled? I did have a cracked header and replaced them during all of this as well but I did still have the misfire after doing this as well as a full tuneup and CPS replacement...so...

Any way I'm happy to report the new 715 injectors seem to be working great...I've been driving it for three days now with no issues at all...
Too soon to see any MPG improvements but time will tell..

Now the gen/alt light has come on and my belt was squealing so It looks like my truck has decided to move on to the next set of issues.... I just sprayed it with belt dressing so hopefully that helps...
I'd like to get the new shocks and lift installed next week weather permittting... the old shocks are totally blown... you can rock it and it keeps rocking...

 

belt dressing is actually not a good idea. even belt manufacturers wonder why the stuff was even created. Probably by the dealership to stop squealing temporarily so they don't have to replace pulleys....until CATASTROPHIC failure.

 

Siemens 53030778- not my first choice...

Bosch (FMS) 0280156013-

Bosch 0280155934 <- these are what I replaced... 23.6#hour, 248cc min @ 43.5psi

Bosch (FMS) XR3E <- this is what I run; 24# hour, 252cc min @ 43.5psi

Bosch (FMS) XF2E-C4B <- these are 19# injectors... they are advertised as 22#.. maybe they are @ 49psi, but @ 43.5psi they are 19#.. they will work, but they will ride high in the duty cycle and your LTFT will be nearing 'fault status' high it is my opinion.. worst choice listed imHo..

 

I've been driving around for a few days with torque monitoring my fuel trims and I have to say my fuel trim hasnt gone over + 14 or under -20 (just for a second or two on decelleration) so even though these "715" would be considered 21lb injectors they are keeping in tune with the stocker just fine...

 

I wonder what your PCM expects your injectors to flow.. I wonder how much deviation between model years, or from Cali to Fed emissions.. There has got to be a simple explanation as to why there are such injector differences...

my thoughts are that the PCM controls the pulse width in a broader sense on the earlier models, and tightens the pulse up on the later models.. meaning the volume delivered for earlier models has to be closer to what's actually required than the newer models..

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(this isn't how it works- i'm just using it to illustrate my opinion)-
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PCM via o2 recognizes lean condition....

PCM sends 1.5millisecond (say, +1%) longer time lapsed signal to injectors to fatten mix. the PCM reports an increase of +1% (in my little illustration) Short Term Fuel Trim..

injector receives instruction to stay open 1 millisecond longer, fattening the load..

o2 sensor reports to PCM mix is closer to Stoich once the +1% seems to do the trick over an extended period of time, and alters the Long Term Fuel Trim to compensate for the STFT alteration..
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if YOUR PCM believes your injectors are capable of delivering 225cc/min, and MY PCM believes my injectors are capable of delivering 248cc/min, the same % of increments for adjustments will be MUCH different in the volume of that adjustment..

if this is true:

if you were to put heavier injectors on your truck, and your PCM determines there is a lean condition and needs to add fuel @ a rate of +4%, it may try to add a scripted +4%, but the volume of that +4% will be the equivalent of +7% of actual fuel delivered.. which means it will PULL fuel on the next o2 cycle.. just to find it needs more on the next cycle.. it goes into a tizzy trying to FIND stoich.. which accounts for whole point bounces up and down that don't seem to make sense when monitoring fuel trims..

I don't think the PCM is capable of 'learning' the volume of it's increments.. I think that is hard scripted and can't change.. if this is the case, it kinda explains why trims are all over the place- it is screaming "but Captain, I'm giving her all she's got" @ +30%, when in actuality you're just using an injector that is too small for the task.. or, on the flip side, it's screaming "I've cut it as much as I can!" @ -30%, because you're using injectors that are much larger than what is needed...

the PCM, using injectors closer to what is expected, would be delivering the precise same fuel (in volume) as it is with those two extremes, but report "eh, +9% LTFT, -.08% STFT, we're good here, Boss".. <- which is why I believe there are differences in model years and emissions on our trucks, and why injectors are a dangerous game to play without using BOTH monitoring software, AND a a/f gauge to tune..

I think that scripting changed several times between '96 and '02/3.. It's a transparent change to us- but not to the PCM/engine.. it's pretty dang significant to the PCM/engine..

 

I mistakenly said 715 ... its the 712's im running and they should deliver just under 23lbs of fuel at 49psi...which is close to the 23.2lbs ive been told the stock 778 injectors deliver... and yeah the bigger703 injectors seem to work in the 95 and older models even though the flow was less at 39 psi...