I recently replaced my Purge Control Valve to fix my P0444 code and it worked, although it popped back up, not sure what I need to do. As far as the P0157, I have no clue what I need to do in order to clear it, I'll do my due dilligence and research to see what I can find. But I'd like a direct answer from a 350z owner who has encountered a similar issue.

I do have a snapped bolt when I installed my Plenum Spacer and have left it untouched due to me being told it would be fine. Is that an urgent fix? I'm driving an 2006 Nissan 350z Base Model. I have noticed that when accelerating, the RPMs climb roughly and not smooth, if that makes sense.. And recently, I've noticed my car sounds "deeper" and slightly sluggish. I'm not a good at diagnosing but is it possible my engine is misfiring? Any help and tips would be great. I've owned my Z for about a year now and am still new to working on cars especially working on my Z, I'd rather do everything myself instead of relying on a mechanic.

 

From my basic research, most people attribute the P0444 code to a bad or not connected wiring harness, incorrectly installed or cracked vacuum hoses, and potential vacuum leaks caused by a plenum spacer. Start by looking at those basics first. I'm not sure if your engine is a DE, HR, or Rev Up, so go here to find the full service manual for your specific year and then click on "Engine Control System" to find extra info on diagnosing P0444. (The full service manuals, or simply FSMs, are really great resources for diagnosing and learning about problems with your Z.) I am dealing with a similar code, P0443, and I ended up biting the bullet and going to a real professional mechanic to see if they could fix the problems with my EVAP system. (This is my thread documenting what I've done so far to try and fix it: check back here in a few days since I'll post what the professional mechanic found, as it could help you too.)

P0157 is an O2 sensor code it appears. Probably just need to replace it, don't make the mistake of going with non-OEM/cheapo O2 sensors. (I did and now I'm in a perpetual battle against one O2 sensor that I just can't seem to fix lol.)

 

The plenum spacer install gone wrong is where I would start. A broken bolt can cause a vacuum leak, especially if it's one of the center 6 bolts. If you didn't install the center support spacers correctly with the OEM internal gasket (sits around the lower plenum gallery), you're going to have problems.

As MoneyPitz mentioned, you need to double check vacuum hoses. The obvious ones to check are the PCV hoses since those need to be disconnected when removing the upper plenum and intake. There's a 3rd PCV hose that connects between the valve covers under the lower intake (just behind the upper timing case). Odds are those hoses are original and hard as a rock and could have cracked or split. You should replace with new OEM hoses. Another vacuum hose to check is the brake booster line, this runs from the passenger side intake plenum to the false firewall where the battery and fuse box is located.

For P0444, you could have a wiring fault or bad purge valve. Where did you source the replacement valve?
For P0157, I agree with Money's assessment. Most likely a bad O2 sensor, in rare instances it could be faulty wiring.

If you live in a rust belt area or your car is suffering from corrosion/rust. I would inspect and clean grounds around the engine bay. Modern vehicle sensors/electronics are very sensitive to getting proper voltage/amperage, all kinds of weird things can happen if you have poor ground connections or a weak battery/charging-system.. If you have a bi-directional OBD tool, you can do an actuation test on the purge valve. Using the harness plug with a volt meter or test light to see if the wiring is good.

Good Luck!
-Icer

 

I see, I have a DE, I'll take a hard look at my vacuum hoses and definitely take care of my stripped bolt on my Plenum Spacer. I replaced one O2 Sensor from Rock Auto and I'm assuming the other one has gone bad. Do you have any reccomendations of a good OEM/OEM+ O2 Sensors?

 

I'll definitely start on the Plenum, although it's not one of the center 6 bolts, I have a feeling it could be a problem. I appreciate the advice and tips, I'll see what I can do and post an update later.

I replaced the Purge Valve with a random one I got on Rock Auto, and I haven't thought about rusty grounds, I'll take a look into that as well.

 

When it comes to sensors related to the Ignition System, I always recommend sticking with OEM. YES, they are expensive, but it's better to solve the problem with your 1st shot vs. trying to save some cash only to find out the part is garbage (and not returnable/refundable) and end up spending more money on the genuine part anyway. Adding insult to injury, you now have to go back under the hood and spend more time doing the job twice. I used to purchase from Rockauto a lot, but in recent years I think they're having quality assurance issues. There have been alleged cases of counterfeit parts being sold through Rockauto. The chinesium counterfeits are getting very good at looking genuine, you would need to be an experienced technician or parts counter guy to notice the subtle differences. I will still use Rockauto for parts, just not stuff like sensors, spark plugs, and ignition coils. The market is flooded with counterfeit parts in those categories. Ebay and Amazon are also very hazardous if you can't spot counterfeits. Rule of thumb, if it's too good to be true, then it's probably junk. Exceptions would be used parts on Ebay from wreckers and salvage yards.

You don't have to purchase OEM parts straight from a local dealership. I purchase plenty of OEM parts from online dealerships like nissanpartsdeal.com, conceptzperformance.com, and z1motorsports.com.

Doing some price checks. It looks like the best price for an '06 VQ35DE OEM O2 sensor (P/N: 22693-CD700) is from Nissan Parts Deal ($173.00). But I always price it out after shipping and tax is factored in. These large online dealers tend to charge high shipping prices. Typically when I use them, I do bulk/bundled orders. For example, ordering some small clips or bolts that cost less than $10 and then paying 20$ shipping isn't worth it, at that point I'll use my local dealer or another online parts seller.

Hope this helps! Good Luck!
Cheers!
-Icer