If new knock sensors don't fix it, I'd suggest putting the EGR system back on if you can. EGR lowers combustion temperatures.

It would be interesting to compare this to stock and find the differences. I'd imagine it would mostly be shift logic, but if fuel were leaned out a bit for economy then this might be related as well.

I'd suggest picking another PCM up at the junkyard and have it programmed now, then stash it in your motorhome just in case. They're usually super cheap these days.

It probably will. I helped a friend with a early-2000'* LS SUV that they bought used with a tune in it. The tune was awful for a large number of reasons. I took it to a dealership so they could return it to stock. The dealership'* computers couldn't tell anything about the load in it. I told them that I'm not surprised and re-confirmed "yes, wipe it and put a stock load on there". It'* been fine ever since. I'm not sure what the foreign loads actually write on the PCM, but it seems pretty weird that nothing else can read some or all of them . . . especially when it'* still doing the same job. It'* not like the PCM has been reassigned to control a dishwasher or something.

Cool thanks, I'm curious how this comes out.

this is on new knock sensors first start 10 mins in

at idle 700 rpm
throttle position 3.92
timing advanace 22.5 to 25.0
mass air flow rate 7.83 g/*
intake air tem 87.8
intake manifold psi 4.7862
fuel trim b1 stort -0.78
fuel trim b1 long -8.59
fuel trim b2 long -5.47
fuel trim banl 1 sensor 1 -3.12
fuel trim bank 2 sensor 1 -0.78

fuel tirm b1 long i guess was not showing at that time when taking numbers



ok got some number for you on fuel trim why playing with RPMs

slowly taking up the rpm at 1500 prm i see fuel trim long term bank 1 and 2 moves about the same to +10.0 then comes down slowly at higher rpm of 2500

short term stay about the same up and down + or - 2 or 3
its to late at night to see if the knock sensors work but it seems to be running sick now with a miss again

1 guy picked up on maybe restricted exhaust so i am all so trying to keep you up to date as i have posts every where on the net
thats why i posted fuel trims here

i am going to do a test for restricted exhaust over the last Exhaust pipe break
when i installed new pipes when i got home 1 may have been pushed to deep into the muffler and the sound did show up after instilling new pipes .. but i have to keep in mind the sound could have been there before new pipes

in the back of my mind i know and sure i did not make a err with making the new pipes but i did think the muffler could be full of trash from it just dumping fuel and at 1 fuel stop by err the wife put E85 in the tank 80gallons but that was 500 gallons ago

but first i well make sure the out come of the new knock sensors

O yeah the EGR system was stopped being installed on latter year 8.1l and the vin i used did not have it

ok there is no restricted exhaust tested from o2 port

my gauge was a 0 to 40 pis so i did not have a lower 1 but the needle never moved on wot or any thing so if i had to guess it 1 to 2 pis
the gauge is good as i used it the day before on some thing else
the new knock sensor seemed to help but not by much
tested again and no knock/tapping intell motor temp gets to 185F comes in slow and get more as temp goes up to 200F
funny thing i just started unplugging things test wot and as soon as i unplugged the map sensor the sound dropped by 70 to 80% with out much loss in power
for the fun of it i did just install a new 70$ map sensor and that did not fix it

At this stage I'm thinking a factory load on your PCM would probably solve it . . . unless it'* something silly like extra-hot plugs.

that would be my luck but it was doing the same thing before new plugs but i have autolite app 5245 in there
i sent a email out to the ECM guy i got it from . found the info so the ecm been working all the way back to 2013
there is still a hard fuel smell coming from exhaust with a really bad miss again when it starts all the way to running temp now
pulled the logs on fuel trip but i really dont know what i am looking at but LTFT on bank 1 goes +10% when on load bank 2 +7 or 8%
its still really funny when i pull the plug on MAP sensor 80% of the tapping goes away or its just really hard at wot to make it tap any more
O put a cam down in cylinder 2 to look for build up on piston and yes there is some from it just dumping fuel buti could not see any thing else wrong like hot valve to cracks
only thing else i can think of is the heath of fuel injector 2 if its cutting out when hot or under load but then if so how would unplugging the map make things better

I agree.

Most of what I'm seeing on this issue tastes like detonation to me. Whether from high combustion pressure or lean burning or whatever, I don't know.

So, taking that notion for a ride: if I were programming a PCM for economy I might lean out the fuel maps a bit. I mean I wouldn't, but I've heard of others doing this. So, let'* say this load works great in many circumstances, I'd think that'* a good load. Maybe something about your engine is a little more or less of something that the PCM assumes. It crosses the line in practical use and causes some detonation.

The biggest factor to me is that it does it when it is warmed up, and not before. When it warms up the fuel mixture leans out. If the custom load for some reason allows it to lean out a bit much then that could be your issue.

I've never personally heard of a dealer load on a PCM have an issue like this on a stock engine. If you have it returned to factory then change the known gear ratio, I'd bet 80% chance the noise is gone based on what I know of it.

thanks for staying with me on this . have 2 things to go over

i got a email back from the ECM guy today here is what he said

"i am confident it'* not the program and i highly doubt it'* the PCM hardware. unless of course it got roasted. it'* an 87 octane map so the timing is stock almost everywhere. it'* may be lean for some unknown reason or other engine related problems."

he know the motor was going in a RV know the GVWR and every thing and the donor vin was from a C5500 or C6500 truck but he side for 350$ he can send me a new ECM to make sure
giving the RV is a custom motor swap i am sure 99% of gm dealers would not help as the ecm needs alot of things turned off like theft .. i think any ways or told my self that


stopped by a few shops todays asking what it would cost for some 1 else to look at it and i nice guy seat down with me for about 30mins and worked over what i did and he told me to look at the fuel injector again
he seems to think with that wire going to ground that the fuel injector is not made for 100% duty and that the fuel injector is hurt in some way and when it gets hot its dropping out so i well do the test he asked me to do

Cool, worth a shot. Let us know how it goes!