'04 V8 P0171/P0174 codes

R

rgorke

Dedicated LVC Member
Joined
Aug 5, 2017
Messages
632
Reaction score
100
Location
Camarillo, CA
First, read through quite a few threads on these codes.

Second, car is running great, 200-300 miles over weekend, go to breakfast this morning and CEL comes on with P0171/P0174 codes.

I will check the following, based upon a Joegr post:

"A lean condition without misfire would possibly be
air/vacuum leak
low fuel pressure
clogged/dirty injectors
Bad TPS
bad/dirty MAF
bad O2 sensors
bad gas"

QUESTION(s):

1) The Crankcase vent tube: A month or more ago, when removing air intake system - pipe, tray, etc (to get to sway bar bushing), I removed the crankcase vent tube from the manifold. I noticed a small piece of the tube where it attaches break off. (Also, was at junk yard the other day and an '06 had the exact same chip out of the attachment tube...same shape, location, and size. Hmmmm.) I haven't had issues until this morning. Is that tube attachment point replaceable?

2) Will codes clear themselves when problem is addressed or do I need to clear them through the OBD2? I want to make sure I fix the problem, not just clear codes.

3) Which vacuum lines should I inspect/replace? The ones attached to air filter intake? Are there others?

4) MAF cleaning? Carb cleaner ok?

Thanks!!!!
 
1. Yes, it's replaceable. Just replace the whole PCV tube. Of course, the odds are that it is no longer available. If it's broken in the way that I think you are describing, it's not really a problem. Mine are too. The plastic gets brittle and breaks instead of bending when you squeeze it to release it. It's just a lock to make sure the tube stays in. Mine have stayed without it.

2. Yes, the code will clear after the issue is not detected for a few cycles.

3. Inspect all, replace any that are leaking. This includes the brake booster hoses.

4. No, there is a specific MAF cleaner spray to use. All the auto stores have it. (Also, don't use carb cleaner on anything. Use throttle-body safe cleaner only on the throttle body, intake, PCV, ...)
 
Thanks Joe....

Here’s a picture of the broken crankcase vent tube attach thingy (can’t find right word...lol).

7A681569-8350-4A46-8A9E-157362F70487.jpeg
 
Oh, I thought you meant the release clip on the hose. You would have to replace the valve cover to fix that. Still, it probably isn't leaking. You can hold an unlit propane torch to it (hose connected) with the engine running to verify. If idle changes, then it is leaking.
 
UPDATE:

Yesterday, I went through and made sure each vacuum hose fitting was securely and snugly attached. I got some MAF cleaner and gave the MAF a good dousing of cleaner and reinstalled. CEL was still on. I put the OBD2 coder back in and saw that the P0171 had cleared and I only had the P0174. I cleared the P0174 and will monitor to see if it comes back on. I drove it 15-20 mins after clearing the P0174 and the CEL stayed off. I'll report back if and when it comes back on.
 
rgorke said:
UPDATE:

Yesterday, I went through and made sure each vacuum hose fitting was securely and snugly attached. I got some MAF cleaner and gave the MAF a good dousing of cleaner and reinstalled. CEL was still on. I put the OBD2 coder back in and saw that the P0171 had cleared and I only had the P0174. I cleared the P0174 and will monitor to see if it comes back on. I drove it 15-20 mins after clearing the P0174 and the CEL stayed off. I'll report back if and when it comes back on.
Click to expand...

Kudos to you if those simple efforts actually took care of the cel. It's nice on the rare occasion when a little elbow grease fixes the problem.
 
A little over a week and a few hundred miles, the codes are back. Both P0171 and P0174 and back.

I have the Dash Command app that I am still learning to use. There are measures for fuel/air ratio and many others. Might there be a measurement that would be useful in helping me find the culprit?
 
Update:

This morning, when taking the spawn to school, the CEL was off. Running the diagnostics it said the P0171 and P0174 were “stored codes”. Then getting home the P0171 was “pending”.

What’s does “stored” mean? That it is still a problem or that it just had that code previously? Still need to find the ultimate solution but it “seems” that the underlying problem is intermittent.
 
Stored just means that it happened at some time since the last PCM reset. It does not indicate that it is (or is not) still an issue. Pending means it's probably a problem right now, but hasn't been seen long enough to actually trigger the light yet.

It could be that the problem actually is intermittent, or it could be that it is on the borderline between passing and failing. If it's a leak that's on the borderline, then a very slightly bigger leak would make it trigger all the time, or a smaller leak would never be detected.
 
joegr said:
Stored just means that it happened at some time since the last PCM reset. It does not indicate that it is (or is not) still an issue. Pending means it's probably a problem right now, but hasn't been seen long enough to actually trigger the light yet.

It could be that the problem actually is intermittent, or it could be that it is on the borderline between passing and failing. If it's a leak that's on the borderline, then a very slightly bigger leak would make it trigger all the time, or a smaller leak would never be detected.
Click to expand...
Hey Joe, is there a diagram of all the vacuum lines that could contribute to these codes. I was thinking that I might go ahead and change out the lines.
 
Well, any of the vacuum lines could be the problem. There is a diagram of the main ones on a label under the hood.
 
I found this to be an oxy sensor going bad. It is intermittent. then finally stays on.
 
I did a smoke test and didn't see any smoke coming out anywhere. I cleaned the MAF, again really well and reseated (is that a word?) the hoses coming to the throttle body and tightened the hose clamps. I also made sure all the other vacuum lines were seated snuggly. And made use the crank case vent hose was snug. This is where part of the nipple coming off the valve cover broke off (see post #3). Started the car back up and no CEL. It is quite confounding.
 
The saga continues...CEL comes on this afternoon driving to pick up spawn at school. This time the codes are P2195: O2 Sensor Signal Biased/Stuck lean (Bank 1 Sensor 1) and P2197: O2 Sensor Signal Biased/Stuck lean (Bank 2 Sensor 1). It does idle a bit rough but runs fine with with the RPMs up.

I did some searching and didn't find too much that isn't related to the original codes. My next thinking is fuel filter replacement. I've been using 91 octane. I had run some Lucas fuel injector cleaner through the system 6 months ago or so. Maybe time for some more?

What about an O2 sensor going bad?

Could this be related to coils? They are only a year and a half old and were replaced by the dealership in July 2016.
 
joegr said:
Did they replace all eight?
Click to expand...

Yes, first just one then the other 7 in July, 2016.

And then....I went and did another visual inspection and got really close listening and thought I heard a faint hiss. I was able to stop the hiss by putting my finger right where the crankcase vent tube connects to the air intake. I put s piece high temp electrical tape over that area and reinserted the crankcase tube. Started up the car and the idle was much smoother. Drove to the market, CEL still on. Came out and restarted car and CEL off.

Possibly a tiny hole that the smoke test didn’t “smoke out”.

So, is there a more permanent fix to small holes in the air intake structure? Maybe some silicon or epoxy or ?

And back to the coils...I have been looking at the repair receipts that have # 5 repaired in 2014 and the other 7 in 7/2016. They refer to “coil assembly”. Now does the “coil assembly” include spark plugs or not? I would hope so...but I am not certain. I may be calling the dealership tomorrow.

FYI, this was my parents car since mile #88. I have all the repair and work receipts, and that helps a lot!!!
 
rgorke said:
Thanks Joe....

Here’s a picture of the broken crankcase vent tube attach thingy (can’t find right word...lol).

View attachment 828567796
Click to expand...

I picked up some Permatex Ultra Black Gasket Maker to seal any potential cracks or leaks at the air intake pipe PCV connector and to fill in the broken area in this picture. I have also ordered a new PCV hose to make certain everything fits nice and snug. Car is idling much better now, even when cold.

Hopefully the codes will stay away.
 
Hopefully final update: codes came back. Installed new fuel filter and 1200 miles later, no codes, no pending codes, no nothing but a smooth running LS!!!

Thanks for all the help...

Ps, did find a petrified mouse stuck under one of the fuel lines. Must have been there at least a year.
 
tireman said:
I found this to be an oxy sensor going bad. It is intermittent. then finally stays on.
Click to expand...

Do you mean #2 in this diagram? The Heated Oxygen Sensor? My CEL came back on 1500 miles and over 2 weeks after I replaced my fuel filter.

I am also thinking of replacing all the vacuum hoses. What size are the hoses? Or is there a kit that has them all?

s6x_us_en_file=n0033492.gif_gen_ref.gif
 
You must log in or register to reply here.

Members online

No members online now.
Total: 169 (members: 0, guests: 169)
Back
Top