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Same New GXP Owner, tube/line question
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Author:  Vengified [ Sun Mar 31, 2019 12:39 pm ]
Post subject:  Same New GXP Owner, tube/line question
So, I think I found my issue with the codes, if anyone looked at my other thread, however I still had 2 codes coming up, P0171, and P0174. Upon further investigation, I found a hissing noise, figured "vacuum leak, this will be easy." But apparently I'm wrong again? The line in question, is shown below, looks like it would be some sort of PCV, though I dont see a valve, and I'm no expert by any means. However, it goes UNDER the plenum, and I dont see a way to reach it, other than removing the intake, which I can see how to do, or removing the power steering pump, which I dont see how to do.

Could anyone shed some light on this, and tell me if it would cause those codes? The hissing noise is very obvious, and its obvious to me, someone put the line in the wrong place, over top of the fuel rail, instead of underneath, and caused the "L" boot on bottom to stretch, and tear at the bend. So how do I get to it, and what is it even called?


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Author:  CMNTMXR57 [ Mon Apr 01, 2019 11:37 am ]
Post subject:  Re: Same New GXP Owner, tube/line question
It is a crankcase vent tube.

When I explode that picture, I see a crack in the little rubber boot where it goes in to the block. That is what I would focus on with this engine... Replacing all the rubber components around the intake/plenum/etc, as that seems to be the issue with these N*'s. With that said, to R&R that, I really think you can probably do it without plenum removal, just need to get in there. But if you got big hands, you might have to remove it.
Author:  Vengified [ Mon Apr 01, 2019 5:59 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
Thanks for the response! I did indeed get it removed, had to remove the power steering pump to get at it though. Still, not as bad as taking the intake off. No auto places had the part, checked dealer, wanted $18 for it. Went to Carquest, found a generic GM PVC elbow for $5 and stuck it back together, worked like a charm! Hopefully it rids me of my 0171 &0174 codes!
Author:  Vengified [ Tue Apr 02, 2019 11:59 am ]
Post subject:  Re: Same New GXP Owner, tube/line question
*UPDATE: I cleared the codes, ran it for a while around the valley, and the codes came back again. I am POSITIVE there is no vacuum leak, I even tried propane test. I know the fuel filter is good as well. I can post the few details my scanner gives me, but I'm not sure what to try next. I'm no expert on computer controlled cars, this is my newest vehicle ever, and I'm kind of lost on what to replace or fix?

Codes PO171 & P0174
FUELSYS 1 CL
FUELSYS 2 CL
LOADPCT% 40.4
ETC(°F) 203
SHRTFT1(%) -3.9
LONGFT1(%) 23.4
SHRTFT2(%) -2.3
LONGFT2(%) 24.2
MAP(inHg) 15.4
RPM(/min) 1818
VSS(mph) 49
SPARKADV(°) 47
IAT(°F) 79
MAF(lb/min) 2.807
TP(%) 12
AIR_STAT OFF

I'm not sure what all of it means really. I sort of understand fuel trims, but not exactly what its telling me to do to fix it? If anyone has a direction to point me, I would REALLY appreciate it!

*EDIT: I DID do a fuel pressure test, and it was 40 with key on, dropped to 38 when running, down to maybe 35 or 36 when opening the throttle, but came right back up to 38 when idling.
Author:  96 SSEi [ Tue Apr 02, 2019 3:49 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
hi, your fuel trims seem high at 1800rpm
compare these readings to 2500- 3000 rpm and idle
if the trims return to normal at higher rpm, its a vacuum leak.
Author:  skregal [ Tue Apr 02, 2019 4:54 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
There are other places on the Northstar that leak air besides the PCV tube.
The intake plenum gaskets are notorious. You probably should have taken
it off when you changed the PCV tube just so you could get a fresh set of
gaskets on it.

Also the rubber connection between the throttle body and intake cracks
and you can't see it or hear the air leak but it causes big problems.
Do a search on here or youtube for Northstar air leaks and you will find
the culprit.
Author:  Vengified [ Tue Apr 02, 2019 6:34 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
It doesnt really seem like the values return to normal at any range so far, so I'm not sure if it is vacuum leak or something else? I will do some more digging for one later this evening when I can though. Until then, here is what I got.

I went and got freeze frame data for idle as follows:
SHORT1 -3.2
LONG1 24.1
SHORT2 -2.8
LONG2 23.8

And at 2519 RPM:
SHORT1 4.7
LONG1 24.2
SHORT2 5.5
LONG2 24.2

I probably should have done the intake, and normally I do any repair I can while I'm working on a car for anything, but our current dwelling frowns upon repairs that could be messy. I plan on going to my fathers this weekend, since hes out in nowhere land with space to do stuff, and i need to flush my heater core, so if I need to do an intake job, I'll do one out there.

I just wanna be sure that it could not be something much simpler like a MAF or MAP or TPS or FPR before I tear the motor apart more extensively. We bought it to be one of our 2 primary vehicles, and with an active 5 year old, a 4 month old, and 2 working adults, we gotta have 2 rigs during the week.

Thanks again to you all for helping this new car noob! Give me an old 454, and I can tear it down and put it back together with my eyes closed, but these new cars got me hesitant about tearing apart much of anything.
Author:  CMNTMXR57 [ Tue Apr 02, 2019 11:29 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
Step by step troubleshooting procedure fro this.

Quote:
DTC P0171 or P0174
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During Closed Loop the PCM adds oxygen sensor inputs and level of purge to calculate Short and Long Term fuel trim adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent . If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. The values for the Short Term fuel trim change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term fuel trim makes coarse adjustments in order to maintain an Air/Fuel Ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and engine load. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.

DTC Descriptors
This diagnostic procedure supports the following DTCs:

• DTC P0171 Fuel Trim System Lean Bank 1

• DTC P0174 Fuel Trim System Lean Bank 2

Conditions for Running the DTC
• DTCs P0030, P0036, P0050, P0056, P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0142, P0150-P0158, P0160, P0161, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0401, P0403, P0404, P0405, P0410, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P0506, P0507, P1133, P1134, P1153, P1154, P1404, are not set.

• The engine coolant temperature (ECT) is between -40 to +127°C (-40 to +261°F).

The intake air temperature (IAT) is more than -7°C (+19.4°F).

• The manifold absolute pressure (MAP) is more than 5 kPa (0.73 psi).

• The vehicle speed is less than 134 km/h (83 mph).

• The engine speed is between 400-6,000 RPM.

• The barometric pressure (BARO) is more than 74 kPa (10.7 psi).

• The mass air flow (MAF) is more than 0.5 g/s.

• The fuel level is more than 10 percent.

• DTC P0171 and P0174 run continuously once the above conditions have been met.

• The engine is in Closed Loop fueling.

Conditions for Setting the DTC
The average long term fuel trim value is above 19 percent.

The above condition is present for 90 seconds.

Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
• The system will go lean if an injector is not suppling enough fuel.

• The system will go lean during high fuel demand.

• Using a scan tool, review the Failure Records. If an intermittent condition is suspected, refer to Intermittent Conditions .

• Excessive resistance in the fuel injector ignition 1 voltage circuit or the fuel injector control circuit may cause the following symptoms:

- Lean condition

- Misfire

- Rough idle

Test Description
The numbers below refer to the step numbers on the diagnostic table.

If no problems are found, a worn cam, worn intake or exhaust values or other engine mechanical failures may be at fault.

Step
Action
Values
Yes
No

Step 1
Did you perform the Diagnostic System Check - Vehicle?
--
Yes: Go to Step 2
No: Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Step 2
Important: If any DTCs are set, other than P0171, refer to those DTCs before continuing.

- Install a scan tool.
- Start and idle the engine at normal operating temperature in Closed Loop.
- Record the Long Term Fuel Trim data.
- Turn OFF the engine.
- Turn ON the ignition, with the engine OFF.
- Review the Freeze Frame/Failure Records and record displayed data for this DTC.

Does the scan tool indicate that the long term fuel trim is greater than the specified value?
Specified Value = 19%

Yes: Go to Step 3
No: Go to Diagnostic Aids

Step 3
Operate engine at idle.

Observe the HO2S parameters with a scan tool.

Are the HO2S parameters within the specified range and fluctuating?
200-800 mV

Yes: Go to Step 4
No: Go to Step 5

Step 4
Turn OFF the engine.

Inspect the following conditions:
• Vacuum hoses for splits, restrictions, and improper connections--Refer to Emission Hose Routing Diagram .

• Ensure that the vehicle has sufficient fuel in tank. If fuel pressure is too low this DTC may set. Refer to Fuel System Diagnosis .

• Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Did you find and correct the condition?
--
Yes: Go to Step 7
No: Go to Step 6

Step 5
Turn OFF the engine.

Inspect for the following conditions:
• The heated oxygen sensor (HO2S) for proper installation

• The electrical connectors and the wires are secured and not contacting the exhaust system

Inspect for a short between the signal circuit and the low reference circuit.

Did you find and correct the condition?
--
Yes: Go to Step 4
No: Go to Fuel System Diagnosis

Step 6
Operate the engine at idle and inspect for the following conditions:

• Any missing, loose, or leaking exhaust components

• Any vacuum leaks at the intake manifold and injector O-rings

• The air induction system and air intake ducts for vacuum leaks and restrictions

• The crankcase ventilation system for leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.

Did you find and correct the condition?
--
Yes: Go to Step 7
No: Go to Symptoms - Engine Mechanical in Engine Mechanical

Step 7
Important: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel.

- Turn ON the ignition, with the engine OFF.
- Clear the DTCs with a scan tool.
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?
--
Yes: Go to Step 2
No: Go to Step 8

Step 8
Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?
--
Yes: Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information
No: System OK
Author:  ddalder [ Wed Apr 03, 2019 12:34 am ]
Post subject:  Re: Same New GXP Owner, tube/line question
One other very common problem with (I'd guess) any Northstar is the intake plenum bolts loosen off. A lot of people have reported numerous bolts that were not even finger tight. This of course leads to air leaks. I've personally experienced this with the LD8 in both my Bonneville and DTS, along with the LH2 in my STS. There are 10 of them and the torque spec is 89 lb-in.

Look here for the sequence...
post446019.html?hilit=intake%20torque#p446019
Author:  Vengified [ Wed Apr 03, 2019 2:50 am ]
Post subject:  Re: Same New GXP Owner, tube/line question
Thank you BOTH CMNTMXR57 and daalder! This is a good starting point for me to diagnose this gremlin! I'll triple check everything again tomorrow, including intake bolts, and I have a nice mac torque wrench to verify specs. I dont recall if I thoroughly checked the boot from the filter to intake either. The only other listed diagnostic step, I'll do some research on, is fuel system diagnostics. And maybe invest in a better scan tool that can tell me o2 sensor voltages, as my current one doesnt stem to have it anywhere.

Again, I REALLY appreciate you all sharing your information with me! I can google like anyone else, but getting it from owners/experts with first hand experience, means more than a random wiki article that could be false information. So thanks again.
Author:  CMNTMXR57 [ Wed Apr 03, 2019 12:50 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
Yea, GM and their 89 inch/pound torque spec on these engines. :) Then they use a shoulder bolt that doesn't always offer enough clamping force to be honest. :)

Cam covers also use that torque spec and we all know how that goes with the N* cam covers. :)
Author:  Vengified [ Thu Apr 18, 2019 11:18 am ]
Post subject:  Re: Same New GXP Owner, tube/line question
*UPDATE: So, I thought I would give an update for anyone curious, and I have not had any codes in over 2 weeks. I checked again for leaks, could not find any. I pulled MAF sensor and cleaned it, cleared codes. A few days went by, and got SES light again, but this time it wasnt bank 1 &2 lean, it was just EVAP leak code. Checked again for leaks, this time with engine cold, found none. Checked gas cap, it was tight, seemed fine, but I went ahead and replaced it, just because that was the easiest cheapest fix. VOILA! Erased codes, never came back. To add to that, my STFT and LTFT are now 0.x and 1.x respectively, so a HUGE improvement from the -3 and 23 it was!

Also, replaced the stepper motors (as they were all crazy) and bulbs in instrument cluster, repaired seat heater (except need new module for qpassenger side), and fixed my heater. After doing a heater core flush (which was a PITA), still wasnt getting heat, thought maybe actuator motors, but traced hoses, found a strange "Curly Q" shape, near the coolant reservoir, one side hot, one side cold, squished it a bunch with it running, it let loose, and I have heat! Have also refinished the headlights, and fog lights, and replaced fog bulbs with LEDS (which dont seem bright enough, might go HIDs), and added demon eyes to the fog lamps also.

Now if I could only figure out how to clean the suede, and figure out what to do with my front bumper being cracked, my car would be pretty brand new! Thanks again to everyone's input on my code issues!

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Author:  bobc997615 [ Thu Apr 18, 2019 10:44 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
I cleaned the suede with a Bissell carpet cleaner using the upholstery tool.
Author:  ddalder [ Thu Apr 18, 2019 11:47 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
While it may sound odd, I had really good success using ACDelco glass cleaner, a relatively soft brush and towel for a final wipe. I would try to wipe it of the regular leather so it didn't sit on there too long as it may dull the shine once you spray it on. A professional detailer I've been using for many years frequently does it this was as well (I learned from him).
Author:  CMNTMXR57 [ Fri Apr 19, 2019 2:14 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
Brakekleen?

The core chemical in it is the same as what Dry Cleaners use on your clothes.

When one of our kids spilled something on the couch, I gave my wife a can of Brakekleen and she's been in heaven since. :)
Author:  Vengified [ Fri Apr 19, 2019 5:46 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
I have a carpet shampooer, brake cleaner, and glass cleaner! Lol. Never tried any of the 3. I did try vinegar, and also rubbing alcohol, both with no success. Also got one of those "suede erasers" and a suede brush, and that didnt work either. So, thanks for those tips! I'll try them later this evening. Previous owner had two kids also, looks like they had an ice cream fight and/or leaked all over the backseats...
Author:  CMNTMXR57 [ Fri Apr 19, 2019 5:55 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
The only thing I would worry about with the BrakeKleen is it leaving a mark around the borders of the area you clean.
Author:  Vengified [ Sun Feb 28, 2021 12:16 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
I know this post has been dead for nearly 2 years, but in case someone else ever runs into this issue, I found the final culprit to my code issues:

After replacing gas cap, the evap code eventually came back, after some thorough inspection, I noticed the filler neck was rusted. I cleaned it down to bare metal, and used activator and primer (I work at Safelite and used the same stuff we use for windshield pinch weld repair) and after that, I have gone over a year with no additional codes. I believe the rust was preventing cap from making a good seal, but its solid now!
Author:  CMNTMXR57 [ Mon Mar 08, 2021 4:53 pm ]
Post subject:  Re: Same New GXP Owner, tube/line question
Yup. That seal can cause issues too.
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