LS1 - P0171 and P0174 both banks running lean
11-27-2014, 09:02 AM
#21
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do you have access to a scan tool? If you can look at fuel trims and o2 readings it will help tremendously.
You could need intake gaskets or have a cracked manifold, when everything heats up and expands the leak may seal up. It is something big if its affecting both banks. Check the obvious, any vacuum hoses, keep figuring out your PCV system, throttle body and intake gaskets and inspect the intake manifold closely. Clean your throttle body real well while your at it, oily carbon residue buildup on DBW throttle bodies can cause driveability issues.
You could need intake gaskets or have a cracked manifold, when everything heats up and expands the leak may seal up. It is something big if its affecting both banks. Check the obvious, any vacuum hoses, keep figuring out your PCV system, throttle body and intake gaskets and inspect the intake manifold closely. Clean your throttle body real well while your at it, oily carbon residue buildup on DBW throttle bodies can cause driveability issues.
The dealer told me that the stock gaskets were failure prone and that the current replacement gaskets were an improved design to fix the problem. They did the trick for me.
11-29-2014, 09:39 PM
#22
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Ok - after a flat out week at work I managed to find some time today to work on my problem and some progress (of sorts).
I fitted a pair of new Delco O2 sensors (upstream) and cleaned the TB. Like everything on this motor, the TB was pretty clean to begin with so I just wiped out a bit of black grease from around the butterfly.
Fitting the new sensors was pretty straight forward and things have changed somewhat.
Cold start idle was still terrible but I did realize I forgot to plug the rocker cover vent back into the intake so that may have been my fault - won't know till tomorrow morning.
The code situation has changed however. It still throws a code but only once and the SVS light stays on till I turn off the car. My OBDII reader still doesn't detect a problem though. I did some observing of the O2 voltages and found:
Bank 1, sensor 1 = 0.44V (constant, never changes)
Bank 1, sensor 2 = 0.44V (constant, never changes)
Bank 2, sensor 1 = 0.75 - 0.9V (variable)
Bank 2, sensor 2 = 0.44V (constant, never changes)
Ambient air temp here today is roughly 90deg F.
Sigh..... the saga continues :/
I fitted a pair of new Delco O2 sensors (upstream) and cleaned the TB. Like everything on this motor, the TB was pretty clean to begin with so I just wiped out a bit of black grease from around the butterfly.
Fitting the new sensors was pretty straight forward and things have changed somewhat.
Cold start idle was still terrible but I did realize I forgot to plug the rocker cover vent back into the intake so that may have been my fault - won't know till tomorrow morning.
The code situation has changed however. It still throws a code but only once and the SVS light stays on till I turn off the car. My OBDII reader still doesn't detect a problem though. I did some observing of the O2 voltages and found:
Bank 1, sensor 1 = 0.44V (constant, never changes)
Bank 1, sensor 2 = 0.44V (constant, never changes)
Bank 2, sensor 1 = 0.75 - 0.9V (variable)
Bank 2, sensor 2 = 0.44V (constant, never changes)
Ambient air temp here today is roughly 90deg F.
Sigh..... the saga continues :/
11-29-2014, 09:52 PM
#24
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Just letting it all cool down
Edit: I'm a dork - forgot to plug one of them in
Off for another test to see what's what....
Edit: I'm a dork - forgot to plug one of them in
Off for another test to see what's what....
Last edited by RedHotMike; 11-29-2014 at 10:05 PM.
11-29-2014, 10:18 PM
#25
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I had a 2001 Gmc Yukon throwing same codes with a 5.3 engine. Done everything could think of. Ended up being intake gaskets. The rubber pieces that crush to seal had split in up & down portion on 2 cylinders. ! on each side. Replaced gaskets ended that. Thru no more codes.
11-29-2014, 11:01 PM
#26
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Ok - had a drive and it's far better than it's been in weeks.
Made it 20min down the road without incident. Parked for a few minutes and then started it again and bang! Alarm and SVS code that disappeared after about 30 seconds. Then drove home again without incident.
Made it 20min down the road without incident. Parked for a few minutes and then started it again and bang! Alarm and SVS code that disappeared after about 30 seconds. Then drove home again without incident.
12-02-2014, 11:38 PM
#29
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Have you tried taking the intake manifold out and looking at the gaskets? There was a guy at work that had a broken exhaust spring on a 6.0 Express van. It ended up creating so much pressure it blasted a dime sized hole into the bottom of the intake.
Not saying that is what you will have but I would try taking the manifold out and replacing the gaskets especially at 140k miles
Not saying that is what you will have but I would try taking the manifold out and replacing the gaskets especially at 140k miles
12-03-2014, 03:28 AM
#30
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very slowly at the moment. Unfortunately work is crazy busy which leaves me Sunday morning before I can do the idle reset (not sure the neighbours would appreciate me doing it at 6:00am during the week).
Yeah - it'd be an incredible coincidence if it failed but I can't rule it out. I have sprayed aerostart/brakeclean along the top without making any difference but of course I can't check it on the under side edges. It's a cheap thing to try when I can find a few hours to do it
Have you tried taking the intake manifold out and looking at the gaskets? There was a guy at work that had a broken exhaust spring on a 6.0 Express van. It ended up creating so much pressure it blasted a dime sized hole into the bottom of the intake.
Not saying that is what you will have but I would try taking the manifold out and replacing the gaskets especially at 140k miles
Not saying that is what you will have but I would try taking the manifold out and replacing the gaskets especially at 140k miles
12-06-2014, 11:12 PM
#32
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12-07-2014, 06:03 PM
#33
Smoke test might work but I think at this point you might just replace the intake gaskets. They aren't terribly expensive (~$60 maybe) and shouldn't wake more than a couple of hours. You could inspect the manifold at the same time. Heck--get yourself a LS6 or similar and then you've got an excuse! 
12-10-2014, 06:32 AM
#34
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1. Cold start misfire for the first 10 min or so
2. Throwing P0171 and P0174 codes (always as a pair) during idle (eg sitting at traffic lights) or 0 throttle situations (braking usually at low speed - doesn't seem to happen ever above 30mph). This will happen even at normal operating temperatures. After the car is up to normal operating temp the idle will be perfect.
Have you checked your brake booster and line going to it? Also have you checked fuel pressure?
2. Throwing P0171 and P0174 codes (always as a pair) during idle (eg sitting at traffic lights) or 0 throttle situations (braking usually at low speed - doesn't seem to happen ever above 30mph). This will happen even at normal operating temperatures. After the car is up to normal operating temp the idle will be perfect.
Have you checked your brake booster and line going to it? Also have you checked fuel pressure?
12-10-2014, 03:56 PM
#35
Well, I have some more info on my codes. Only have 200 miles on the takeout engine/trans and have no idea what the actually miliage is. Engine is box stock. Will usually set the codes in the first 5 minutes of driving but after that it will be fine except if I get on it a little they will set again. This afternoon I ran around some and all of a sudden it started to have a cyclic chirp like a fan belt noise. As near as I can determine it is coming from the center of the engine about valley high. The chirp does not seem to be RPM related and is best heard at idle and only at full operating temp. Could this be caused by an intake gasket around one of the center cylinders? Only "chirps" on that cylinders' intake stroke? As a side question is it OK to clear codes while driving?
12-10-2014, 11:52 PM
#38
code P0171, P0174 Guess I didn't make myself clear. The noise can be heard at idle but when reving th engine, background noise drowns out the chirp and can't hear it. I had the intake off during the build and did install a new gasket. Tomorrow I'm going to pull the intake. Hopefully I will find a failed gasket. Stay tuned.
12-11-2014, 05:07 PM
#39
Hopefully that helps you. What I mean is that if the cyclical "chirp" is caused by the intake stroke of a cylinder, as RPMs increase, the frequency of said chirp would seem to increase because the intake stroke happens once per RPM--higher RPM should result in more chirps. Also, keep in mind that at even a 600RPM idle, the intake stroke for a cylinder would be occurring 10 times a second. But maybe it's not every stroke and maybe at higher RPM it's just sucking too much air to produce a notable chirp or the additional vacuum even causes the leak to seal up?
Just thinking out loud.
Good luck with your issue.
Just thinking out loud.
Good luck with your issue.
12-11-2014, 05:30 PM
#40
code P0171, P0174 Took the intake off and guess what....nothing! Can't see any signs of a failed gasket or anything else amiss. Did find a leak on the oil sending unit. Easy to tighten with the intake off. Just got it back together and started. No chirp but didn't road test. Will do that tomorrow and see what happens. Wonder if my large induction with a large K & N filter is sucking more air that programmed for and causing a lean condition?