Codes p0171 and p0174

[Diogenes]

Hey folks!! Just failed emissions.. "sigh" because there's apparently no input from the O2 sensors.

My rig is a 1999 with only 60K miles on it (yes.. that's correct.. , so I'm thinking it might be a MAF related issue and I'd like to explore this before paying the $$$ to take it to a mechanic..

So what kind of MAF related cleaner should I be looking for and how do I use it? Do I just remove the air filter and spray it into the air intake tunnel? I take it I should not do this with the motor running.. ;0)

Btw, haven't had the codes read yet, so this is just a first step.. trying to avoid a major (costly) repair bill if I can.

Thanks for any input you can provide!!

[Diogenes]

Just had my vehicle down at the shop to have the codes read and they informed me that to replace my 02 sensors (all 4 rather than just 1), they'd like to charge me $850..

I declined, but asked for a written estimate since in our state, if the cost of repairs is over $750 to bring the vehicle into emissions compliance, you apparently can get a waiver.

I'll try and deal with the 02 sensors on my own time and see if I can fix/replace them myself.

Diogenes

[johnnyapollo]

They sell for about $50 each on eBay (and sometimes you can get them a lot cheaper - think I paid $14 for the last one I found on there). I'm not sure why they're charging you so much in labor - I think the sensors retail for something like $79 each. It could be an exhaust/emissions issue that is unrelated to the sensors.

-- John

[Triathlete]

To clean the MAF you just loosen the two clamps (one on each side of the MAF) and remove it. You then spray the inner parts of the MAF, according to the dirrections on the can, with MAF cleaner (any auto parts store should carry it...it is a cleaner made specifically for MAFs). I used "CSC Mass Air Flow Sensor Cleaner" that I bought from Checker Auto. It is fairly inexspensive.
As far as the o2 sensors...they are pretty easy to access. They are on the exhaust pipe. If you crawl under the VX you will see them pretty easily. Just pre-soak them with a penitrating oil 3-4 times prior to help loosen then up. Just need the right size wrench and a little elbow grease and you'll be good. Probably less than a 2 hour job if you take your time. As stated already, the sensors are under $80 each. I know checkers has the Bosch sensors for about $75 regular price.
If your state is like Az then you can only get 1 waiver so this is not a long term solution.

[volume311]

I got a pair of new Bosch O2 Sensors for about $55 down here with the harness.

You will need either an O2 sensor wrench or a open ended 22mm wrench. Spray them with some PB Blaster first and they pop right out. Do it in the morning when the pipes are still cold, they heat up pretty quickly. The hardest part on the front ones is getting to the connectors.

[Vehi-Cross-Az]

good thread, and info
just wanted to add my 2¢ for those who want to clean
their MAF sensors.
When I do mine, I take mine off completely
I use white vineger (a mild acid) to clean mine.
Its cheap, works great and plenty of it around.
You can even soak the wire in the vinegar in a bowl
if you want for a few hours..
And when done just rinse it off with warm water.
Let air dry and install.

Triathlete, you should try to swing by my shop
someday. Its on 1st ave just north of Grant rd.

[WormGod]

Just cleared out my 171 and 174 codes this weekend. An intake tear down and a solid blast of MAF cleaner did the trick. Did not bother with the o2 sensors. I just passed emissions about 3 weeks ago (CEL didnt spawn until 2 days after I passed, heh), so I am in no immediate hurry. I will just wait and see if the sensors themselves decide to throw a CEL (I believe that is a 420 if I am not mistaken).

Thought this may be related at first since both popped up about the same time, but it does not appear so. Even after cleaning the MAF and clearing the codes, my VX is still running.... funky. On cold startup, it idles at roughly 2k-2300k. On warm startup, sometimes it simply stalls at idle unless given some juice. This is all new as the S/C has been in for almost 2 years now. I am leaning towards the FPR and/or the EGR. Both were fully prepped and cleaned when I installed my S/C, but considering I have 7 hard years on both, it wouldn't hurt to replace. It may also be one of the reasons why the VX has started to run a bit lean and is suffering minor fuel dump. Thoughts?

[Ldub]

Just cleared out my 171 and 174 codes this weekend. An intake tear down and a solid blast of MAF cleaner did the trick. Did not bother with the o2 sensors. I just passed emissions about 3 weeks ago (CEL didnt spawn until 2 days after I passed, heh), so I am in no immediate hurry. I will just wait and see if the sensors themselves decide to throw a CEL (I believe that is a 420 if I am not mistaken).

Thought this may be related at first since both popped up about the same time, but it does not appear so. Even after cleaning the MAF and clearing the codes, my VX is still running.... funky. On cold startup, it idles at roughly 2k-2300k. On warm startup, sometimes it simply stalls at idle unless given some juice. This is all new as the S/C has been in for almost 2 years now. I am leaning towards the FPR and/or the EGR. Both were fully prepped and cleaned when I installed my S/C, but considering I have 7 hard years on both, it wouldn't hurt to replace. It may also be one of the reasons why the VX has started to run a bit lean and is suffering minor fuel dump. Thoughts?

FPR could be a contributing factor, especially if you didn't pop in a new one when you installed the S-C. BTW, you can get a right angle snap ring pliers that JUST has enough clearance, at Harbor Freight for cheap...
The one I got has straight, 45 deg. & 90 deg. interchangable jaws.
Also, the snap ring that comes with a new FPR is too small for the aluminium block on the S-C kit, so re-use the old one.
The lean condition that the codes are indicating, from my past experience, points towards a vacuum leak, either intake gaskets or vac. line.
I've had vac. lines pop off under boost, also check the PCV valve & hose, I recently had the same exact symptoms & it turned out that I had a bad PCV valve. (the top & bottom had come apart)

[WormGod]

I replaced the PCV a few months ago, as well as my temp sensor, so I think those should be good to go. All vacuum lines were pretty solid though I was skeptical of my plumbing for my CAI. I removed all of it up to throttle body and replaced it with the OEM air box, for now anyways. I thin kI am gonna do this in increments and get a new FPR first and see how that goes. I didn't replace it with my S/C install, so I don't imagine it would be a bad option.... except on my wallet in this lovely !@#$ing economic doomsday.

And speaking of which, going back to the air box, my ScanGauge relays that my fAI is about 20f cooler than it was with my CAI plumbed into the fender port. Some food for thought and means I am gonna have to, once again, head back to the drawing board. Not at all what I was expecting.

[WormGod]

Dag nebbit! CELs came back today after a stall just after startup. *sigh*

First it threw the 174 and then the 171. Looks like I am gonna go the o2 sensors route now. See if I can hunt down some bargains....

[VehiGAZ]

Gary, for what it's worth, I suggest you try a new MAF first instead of O2 sensors. Cleaning an MAF can help if you run a K&N, which will muck it up sooner or later, but MAFs just go after a while, in which case cleaning won't help. Your symptoms are consistent with the ones I had with a bad MAF last winter.

[WormGod]

Wallet allowing, I have a few things planned in the near future so that I can hopefully avoid any later issues.

Looking at replacing the o2 sensors, fuel pressure regulator, EGR, and I will take your advice on the MAF into consideration. I lost $8k in the last 3 months in the stock market so I am gonna be watching my spending a bit more closely so I can keep my nest egg secured.

[taylorRichie]

Just tripped the two codes on the way to the office this morning.

Based on this thread I'm thinking I should clean the MAF and see if that does the trick.

If it doesn't work out then, 02 sensors, FPR, and EGR? What about a PCV clean or replace?

Suggestions?

I'm only at ~52,000 miles. Also this is the first tank of gas I went with 85 octane instead of the normal 88 or 91, could the octane change cause a lean condition?

Thanks guys!

Richie

Glad I did the search and found this wonderful thread.

[tom4bren]

"could the octane change cause a lean condition?"

I'd say no but then everyone would beat me up so I won't.

I've always operated on the KISS principle when tracking down problems. Clean the MAS & reset the 'puter. If codes come back, try going back to higher octane & throwing in some gas treatment. If codes are still there, move onto FPR then EGR then O2.

[don moore]

i took out my mass air flow screen out ..like i did with my vette...Im glad we dont have checks here..