SOLVED: laundry list of DTCs... self-diagnosis forthcoming

[Philberto]

Hey everybody, long time no see!

Hooked my TB up to the nice fancy DTC thing at work, pulled no less than 4 codes. One of these codes is easily explained, but the others will take some work to figure out. I am posting everything up here to both help others through the diagnostic process and to get ideas from all the geniuses here.

Firstly, here is my current situation:

86,139 miles (1,139 mi overdue for an oil change based on my 5k mi intervals)

I use Mobil 1 synthetic, hence the longer intervals.

Spark plugs have never been changed

I damaged my AIR pump connector during the awesome Big Bear trip, and now my car sounds like an angry spray can when I first start it up.

My air filter is probably filthy.



Secondly, here are my DTCs and descriptions:

P0106 - Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance (Current)

P0171 - System Too Lean (Current)

P0300 - Random/Multiple Cylinder Misfire Detected (Current) (Pending)

P0411 - Secondary Air Injection System Incorrect Flow Detected (Current)



I can rule out the P0411 as my damaged AIR pump connector, so that leaves me with an erroneous MAP, lean system, and a misfire.

My thoughts:

Since I'm at 85k miles and have never done spark plugs, here is the procedure I plan to follow, in order:

-Change Air Filter
-Utilize GM Top End Cleaner
-Seafoam the injectors
-Change Oil and Filter, change spark plugs
-Repair AIR pump connection
-Reset DTCs
-Drive and observe for problems.


Thoughts? I'll update as I do all this.

[Diacom]

Possible that a ground strap was damaged as well? Bad grounding can cause multiple codes that will be difficult to diagnose. Might be something to look for if after you run through your intended list codes pop back up.

[Philberto]

After looking at a monitor readout, I've seen that my long-term fuel trim is 24.2%, whereas my short term trim is 11.7%. I'm led to believe that this is the result of a vacuum leak I'm missing somewhere, so the investigation continues. Instantaneous readouts from idle are here:

MIL STATUS: ON

NUMBER OF DIAGNOSIS CODES: 4

FUEL SYSTEM 1 STATUS: CL

FUEL SYSTEM 2 STATUS: -

CALCULATED LOAD VALUE: 25.8%

ENGINE COOLANT TEMPERATURE: 181 F

SHORT TERM FUEL TRIM - BANK 1: 11.7%

LONG TERM FUEL TRIM - BANK 1: 24.2%

MANIFOLD ABSOLUTE PRESSURE: -9 PSI (GAUGE)

ENGINE REVOLUTION SPEED: 598.5 RPM

VEHICLE SPEED: 0MPH

IGNITION TIMING ADVANCE: 7.0 DEGREES

INTAKE AIR TEMPERATURE: 86 F

ABS. THROTTLE POSITION SSR: 17.2%

OXYGEN SENSOR OUTPUT VOLTAGE (B1-S1): 0.120V
SHORT TERM FUEL TRIM (B1-S1): 11.7%

OXYGEN SENSOR OUTPUT VOLTAGE (B1-S2): 0.695V
SHORT TERM FUEL TRIM (B1-S2): 99.2%

DISTANCE WHEN MIL IS ON: 214MI

AIR FLOW RATE FROM MASS AIR FLOW SENSOR: 3.78 G/S

COMMANDED SECONDARY AIR STATUS: OFF

[Philberto]

Well, I am having the oil changed today... I seafoam'd the engine (fuel, oil, and intake) last night, to a great big cloud of smoke, and the light turned off today, so we'll see if it stays off. I looked for a vacuum leak, but alas none was to be found. They're doing an alignment as well, and I'm changing the air filter as well, so we'll see how everything works out. Spark plugs are next on the list, and I've already purchased them, so it's just a matter of changing them. I'll keep you guys posted.

[Philberto]

Problem 1: Failed MAF sensor. Cost so far: $80

[Zero]

If you have an aftermarket intake with an oiled filter, this could be the cause of your failed MAF sensor. For this reason is why many manufacturers now offer "dry" filters. I personally prefer a dry filter, with a pre filter wrap / bag for very dusty or water conditions.

Just thought Id throw that out there. Glad to hear your getting things fixed up. Good luck.

[Philberto]

Nope, factory filter all the way. New MAF seems to have fixed the problem for now... we'll see.

[Philberto]

Well how's this for resurrecting a dead thread (not to mention a comatose account)

I had sort of let this problem slide, what with the massive amount of work I've been doing lately, but thanks to California's wonderful smog check every 2 years, I have finally been forced to resolve this issue before the end of the month.

Here's the current situation:

DTCs: P0171 (System too lean - Bank 1) & P0306 (Cylinder 6 Misfire)

MAF was replaced, to no effect, fuel system cleaning and engine cleaning have been done.

Vehicle now idles roughly and stalls on sporadic startups when engine is cold, but once it has warmed up, everything seems fine. Only occasionally when stopping at a light (once every few weeks), does the engine begin to stumble and sometimes die.

I just got back from Autozone, armed with a new air filter, MAF sensor cleaner, new vacuum tubing, and replacements for my burnt-out headlamp and brake lamp. I have both upstream and downstream O2 sensors on order and coming in tomorrow and Tuesday respectively, and I have 6 OEM spark plugs in my garage with anti-seize and dielectric grease.

Now, anybody have any thoughts? I am trying to see if I may have missed something in my mad rush to get all the parts.




P.S. I may also have some hydraulic "parts" coming in from BDS as soon as I decipher which boots to order with them. I know it's unrelated, but I didn't find the answer and figured I'd throw it in here. --edit: found out about the boots, just took a little digging.


P.P.S. It's nice to see everybody again! I know I've been AWOL, but the financial payoff is worth it, and the TB is finally getting some much-needed TLC. I love the front page redesign, and look forward to picking up a 2012 calendar and making some of my own photos for 2013.

[navigator]

have you replaced your thermostat and temperature sender lately? I would think that would make you run rich and not lean but if you aren't running exactly 210 I would change them.

What about the camshaft position actuator? Sometimes they get clogged up or the screens get torn.
My truck also ran rough when my camshaft position sensor was going out but it threw a code that indicated as such.
You mention fuel system cleaning, does that include cleaning the throttle body? I know that might be obvious to most but don't want to miss it.

I think those are common culprits in a rough running vehicle that I can't see that you have addressed yet.
If I were you, I would start with what you have (02 sensors, plugs etc) and if that doesn't clear it up move on to the ones listed above.
If I'm not running 210 I would go ahead and change the thermostat and temp sender.
I would go ahead and clean the camshaft position actuator and throttle body as well since that only costs time.

[Trail X]

Ahh, good old P030X... good luck with that code. There are a few of us that have struggled to fix that issue. There are essentially 4 possibilities: spark plug, coil, fuel injector, or compression. But sometimes (in Randy's case) none of them seem to be the issue. If your sparks don't seem to fix your issue, look into replacing the coil on #6. If that doesn't fix it, do a compression check, if that doesn't yield poor results, it could be the #6 injector. If that still doesn't fix it, it might not be #6 at all!

[Philberto]

have you replaced your thermostat and temperature sender lately? I would think that would make you run rich and not lean but if you aren't running exactly 210 I would change them.

What about the camshaft position actuator? Sometimes they get clogged up or the screens get torn.
My truck also ran rough when my camshaft position sensor was going out but it threw a code that indicated as such.
You mention fuel system cleaning, does that include cleaning the throttle body? I know that might be obvious to most but don't want to miss it.

I think those are common culprits in a rough running vehicle that I can't see that you have addressed yet.
If I were you, I would start with what you have (02 sensors, plugs etc) and if that doesn't clear it up move on to the ones listed above.
If I'm not running 210 I would go ahead and change the thermostat and temp sender.
I would go ahead and clean the camshaft position actuator and throttle body as well since that only costs time.

Based upon checking with Torque (best value ever, that bluetooth OBDII adapter), temp is fine at 210.

If it was the CPA, wouldn't a code be thrown? Something to check, but not keen on going on a parts-replacing frenzy if I don't have to.

Throttle body cleaning is going to be part of changing the spark plugs, since I'm going to have the intake plenum off anyways, and I might as well clean the CPA at the same time as well.

Ahh, good old P030X... good luck with that code. There are a few of us that have struggled to fix that issue. There are essentially 4 possibilities: spark plug, coil, fuel injector, or compression. But sometimes (in Randy's case) none of them seem to be the issue. If your sparks don't seem to fix your issue, look into replacing the coil on #6. If that doesn't fix it, do a compression check, if that doesn't yield poor results, it could be the #6 injector. If that still doesn't fix it, it might not be #6 at all!

Yeah, I'm hoping it's either a slowly failing O2 sensor or spark plugs. I don't necessarily believe that it's confined to cylinder 6, as previously the code was the ambiguous P0300 code (random cylinder misfire). Given that the engine mostly has rough running and misses on cold starts, O2 seems the way to go for me, unless it's a vacuum leak.

[bgwolfpack]

"DTCs: P0171 (System too lean - Bank 1) & P0306 (Cylinder 6 Misfire)"

Because we only have the one bank, this says either O2 sensor or injector. IMO (although I've been known to be wrong)

[Philberto]

Problem resolved. After the TB stopped idling, had to have it towed to shop. Problem? Cracked intake manifold. Cause? Likely the "melted" oxygen sensors that were causing the CEL. Vehicle now running smooth as butter.

[bgwolfpack]

Butter


Great news!

I've not heard of cracked intakes on the LL8. Was there a cause given?

[Philberto]

Butter


Great news!

I've not heard of cracked intakes on the LL8. Was there a cause given?

No cause was told me, but I am rather curious about it. Any thoughts?

[bgwolfpack]

I wonder if coils had been changed at some point? Other then that, a loose intake may warp I guess but cracked seems unexpected.

[Trail X]

Improper installation or disassembly. Or something heavy falls on your intake? You did SEE the fracture, right? Was the crack near cyl 6? That could indeed be a cause of a lean mixture.

Curious, does anyone else's A/F ratio on their scangauge only display a static number? I'm guessing that's mainly derived from the O2 sensor? The more I think of it, the more I think my oxy sensor is dead.

[Philberto]

I did indeed see and hear the fracture (vacuum leak was quite clearly audible, when I could get the engine to idle for more than 10 seconds) and it was around cyl. 6. I suspect that with the O2 sensors dying, and my slow response to the CEL, the lean mixture caused excessive heat which damaged the intake.