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2008 driveability issues

  • ed begley
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15 Aug 2019 20:18 #32849 by ed begley
2008 driveability issues was created by ed begley
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

any help would be helpful
thanks Ed

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15 Aug 2019 21:08 #32850 by simclardy
Replied by simclardy on topic 2008 driveability issues
What about clogged fuel injectors? Can you scope them? Just thought you might have pulled some debris up from the tank when she ran dry?

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16 Aug 2019 01:28 #32854 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic 2008 driveability issues
My first move would be to drive B1S1 high to see how the computer responds.

" Welcome to the 21st"


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16 Aug 2019 02:41 - 16 Aug 2019 02:42 #32855 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic 2008 driveability issues

" Welcome to the 21st"


Last edit: 16 Aug 2019 02:42 by Andy.MacFadyen.

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  • Tyler
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16 Aug 2019 15:21 #32861 by Tyler
Replied by Tyler on topic 2008 driveability issues
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.

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  • ed begley
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17 Aug 2019 18:38 #32891 by ed begley
Replied by ed begley on topic 2008 driveability issues
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

thanks ed

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  • ed begley
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17 Aug 2019 18:41 #32892 by ed begley
Replied by ed begley on topic 2008 driveability issues
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

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17 Aug 2019 18:43 #32893 by ed begley
Replied by ed begley on topic 2008 driveability issues
remove and cleaned drivers side injectors , seems to idle better , but will not rev past 4k

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17 Aug 2019 20:47 #32897 by simclardy
Replied by simclardy on topic 2008 driveability issues
I've heard some cars have lower rev limits in park. You might be good to go? Try it in neutral or drive. Cheers

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  • ed begley
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17 Aug 2019 21:05 #32898 by ed begley
Replied by ed begley on topic 2008 driveability issues
That would be nice ,i will try it tomorrow

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18 Aug 2019 19:26 #32923 by ed begley
Replied by ed begley on topic 2008 driveability issues
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

thanks ed

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18 Aug 2019 21:06 #32930 by Tutti57
Replied by Tutti57 on topic 2008 driveability issues
Do the fuel trims get better, worse, or stay the same when you raise engine speed?

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18 Aug 2019 21:58 #32932 by ed begley
Replied by ed begley on topic 2008 driveability issues
STFT is 28.1% at idle as soon as raise idle it jumps to 28.9 and stays there
LTFT stays at 24.2% regardless of throttle position

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18 Aug 2019 22:16 #32934 by simclardy
Replied by simclardy on topic 2008 driveability issues
Do you have any misfire info/codes?

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.


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19 Aug 2019 06:15 #32945 by ed begley
Replied by ed begley on topic 2008 driveability issues
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)

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19 Aug 2019 15:51 #32967 by simclardy
Replied by simclardy on topic 2008 driveability issues
Would it be hard to swap bank 1 injectors with bank 2? I would do compression test or swap, depending on which one is easier. Lol

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19 Aug 2019 16:24 #32970 by Tutti57
Replied by Tutti57 on topic 2008 driveability issues
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.

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