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my 2008 gmc 2500 hd 6.0 gas engine 115,00 has developed a driveability issue
2 weeks ago i ran ot of gas ( first dumass thing i did,havent done that since i was 18 years old) reilled tank truck started and ran fine for about 2 weeks
then eng started running extremely rough ,would not go over 20mph horrible nosie from exhaust area check eng light on,. Limped truck home , went under truck banged on left cat and could hear it rattle ,removed expipe removed cat and welded in new cat , removed lh manifold replaced manifold gaskets and broken manifold bolts. Checked ex pipe for any remaining cat debris . Reinstalled expipe I replaced both upstreme and down stream o2 sensors just as a precaution, downstream o2 sensor looked physically damaged after cat failure started unit , unit still runs poorly , accelerates poorly but will go over 20 mph , does not want to rev past 4k , check eng light on code po171
checked fuel pressure key on eng off 47 psi , eng idling 58-62 psi with severe needle fluctuations
STFT B1 28.1%
LTFT B1 24.2%
STFT B2 -7.0%
LTFT B2 -8.8%
O2 B1 S1 0.20v
O2 B1 S2 0.15v
bank 1 readings very sluggish
O2 B2 S1 100-800v
O2 B2 S2 -14.1v
bank 2 seems to fluctuate normally
my scanner has a section for 02 logs
under that heading
there is another LTFT both banks are at 99.2%
my thoughts are that i am running lean most likely caused by a worn fuel pump
i am unsure why i did not set a po 174 , , i dont know if it is because it met parameters to set 171 first
i am a little unclear as why B1 is so sluggish and B2 sems more normal
i have checked for intake leaks at manifold and throttle body none present
i feel as though unit is running lean and trying to compensate by adding fuel but cant due to fuel delivery issue
any way i keep coming back to my fuel pump readings
i have read lot about fuel pumps having a life span of approx 100k to 125k
Based on your fuel trims and lack of accerlation, I'd say you're looking at a restricted bank two catalyst. Your fuel trims are skewed because all the air that should have been consumed by bank two is now finding it's way to bank one, because bank two can't breathe correctly.
I see that you've already replaced the left side cat, which is bank one. It's possible that while the bank one cat was rattling, you actually had a problem with both cats the whole time. :silly:
Backpressure testing is probably your next best move. OR, you can take the cats loose at the manifolds and drive it again. It'll sound like a racecar, but if you can now accelerate, you know where the problem is.
performed your pcm response test
i did have .442 mv bias volatage
when i applied voltage by touching pos and watching scanner O2 voltage went to 1.275v , not as quick as the mitsubishi in your video
now even through i replaced both upstreme and down stream O2 sensors on the pass side , i suppose i could have a defective part , we all had that happen
So i thought if if i swap upstream sensors ,i should see the drivers side O2 which seems to be working start working on the pass side,and the inop O2 sensor on the drivers side stop working on the pass side . That would make sense however both upstreme sensors appears ,perhaps i had a poor connection at the connector and plugging and unplugging made the connection. My B1S2 is still at 0.
Another member suggested that my my B2 cat which i had not replaced may also be clogged, i removed y pipe and ran unit right from the exhaust manifolds, unit still ran poorly when i accelerate it hits 4k and stops almost like it was a rev limiter very consistant , (This was performed in nuetral i dont think there is any type of limiter in neutral i honestly dont know) I have not and the chance to road test it yet i dont expect any improvement
I also remove all for injectors and cleaned them , Idle improved seemed a little smoother , i still have poor O2 numbers on B1S2
What do you think about my fuel pressure numbers, even though i am getting 47 psi which is low according to spec is it possible to get ok numbers for pressure but not have enough volume
removed y pipe , acceleration was the same , this was done in nuetral , i have not driven truck yet , hits 4k and just stops like it hits a rev limiter
forgot to mention that i swapped both down stream sensors ,as expected one that was getting good readings B2S2.is no reading 0 at B1S2, also performed your pcm response test on B1S2 colors were different but the test worked the same reading went to 1.275 , so i believe there are no sorts to grounds or opens.
today i relaced the fuel pump key on eng off pressure went to 52-53 psi
unit felt a little better but my B1S1 numbers are still low varies between .050 and.220 B1S2 is still 0
STFT is 28% LTFT 24%
if the computer is trying to ad this much fuel, i would think that i would have a massive vacuum leak, i do not have a smoke machine but tried the old school method of using carb cleaner at intake manifold throttle body etc,
at this point should i think about performing compression test on the left bank, if it was running lean for to long could i have burned an intake valve , although if this were the case i would think i would have some eng misfire codes for cylinders on the left bank
also during the removal of the exhaust manifold for gasket replacement i damaged one of he spark plug wires ,so i replaced all wires
So we trust the o2 sensor, and you don't suspect leak because of carb cleaner test.
The fuel injector and mechanical problem are still suspect. A combustion test is not a bad idea. I would like to prove the injectors are good.
i do not have any misfire codes at this time.,which surprises me
i did remove all drivers side injectors and cleaned them. i do not have any way to scope injectors at this time. Using a stethoscope i can hear all injectors energizing(clicking)
What are you doing to clean the injectors? I have a bench flow tester and ultrasonic cleaner if you want to ship them to me. Then you'll know for sure. Or do an injector balance test to see if the injectors are the problem.
does it have a MAF sensor if does check related air box and snorkel to throttle body for rips cracks or could unplug sensor see if it improves in limp in mode running off map n rpm take vacuum gage reading at idle then raise engine to 3000 rpm read vacuum does it drop if so plugged exhaust.
cleaning was very diy, i took a tire valve stem remove the injector oring , push the valve stem onto the injector, unscrewd valve cap removed valve core, drilled small hole in valve stem cap so that carb cleaner straw can go thru it screw cap on,valve stem squirt carb cleaner while engergizing injector.I know it sounds a little hokey but i did visually watch the stream improve as i did this a few times
aditionally this problem seems to affect the whole left bank , i would think it would be pretty unlikey that all injectors on just the left side.
i pulled all plugs , all plugs on left side are snow white lean , performed a compression test all cylinders 150 160 psi
so at this point i know mechanically the eng is ok
i cant help but think that i must have a massive vacuum leak that is only affecting the left bank ,
i will trying a smoke test in the next day or so, but i am not sure where to attach smke machine to eng , i dont not have avacuum brake booster so i can not attach there.
I was thinking about tapping a fitting in the snorkel, and then capping it when im done. Also if i hook up through the snorkel will smoke be able to get past the closed throttle plate
I have run into this after customer did same thing. They ended up plugging up fuel injectors . Fuel filter did not stop everything. Also you can have pressure and not volume. There is a quick easy test I can post tomorrow I don’t remember it off top of my head
