I am still tracking down P0171 and p0174 codes on my 06 Z with full exhaust, CAI, and tune. My question is since I no longer have the NPP exhaust, could I have a vacuum leak from the back of the intake manifold on back to the lines running to rear of car? Should I cap off the nipple for NPP on the back of the manifold? Thanks for any help.

Side note I am having my tuner look at the tune next week. I am certain he can fix it. I do not think I have a vacuum leak as the car idles great.

 

Hey Bartsky, my go to guy is Blindspot (Steve) on the forums, try a pm to him, very astute about this stuff
NSF

 

Thank you very much, I recognize that screen name.

 

Cap it off at the manifold and never worry about that possible problem again.

 

Yes, rubber nipple cap off the NPP port is your not using it on the back of the intake manifold., since it allowing air that has not been metered by the MAF sensor into the intake manifold.






Note, if you car did not come with NPP, then should still have the wings section on the port with the port still sealed off. Once you crack the wig section off to install the NPP line, then delete the NPP system, then you need to rubber port cap the port off instead.

 

I should mention that the lines at the rear of the car are capped and I have the fuse pulled, but still wondering if there is a possible vacuum leak between front and back.

 

Capped off line back of manifold, fun part to get to! Maybe just maybe that will fix my lean codes...

 

P0171/174 is lean both banks and often caused by a vacuum leak. Can also be an exhaust leak, but would need to be both sides. Could also be bad O2 sensors, but here too, would have to be both sides.



That said, there is too little to go on here without more details. Specifically, when did the lean codes show? After what event(s)? Also, were the mods and tune done in that order? Or, did you possibly do one of the mods after the tune?



If you really know the manifold port was open and the lean codes came up then, it is pretty good info, that is your problem. Assuming your tune is good, I've seen (and heard about) tuners out there who really don't know how to properly tune headers especially, and with the addition of a CAI. Some simply disable sensors or increase tune tolerances so they don't produce CELs, but they don't know how to set O2 sensor delays to accommodate for the new locations in the headers. That can screw up fueling BC the ECM doesn't know the O2 sensor data coming in is so far delayed from the real combustion event.



Back to the CAI, without knowing the brand, type, etc.; there is a possibility turbulence around the MAF is causing the MAF frequencies to be disrupted. The ECM relies on correct air volume at any given RPM to correctly meter fuel. If, lets say, air turbulence around the MAF at some RPM range causes an incorrectly low frequency, then the ECM will fuel to it, but in reality, there is far more air than is being measured. BUT, a good tuner will know this.


Last thing, if you think you have it now with the intake port plugged, fuel trims will eventually correct themselves and should get back to a normal range IF the tuner set up fueling that way in the first place. Assuming he did, LTFTs move pretty slowly and will take a little driving to correct. But, if you want to accelerate it, and have the capability to erase codes, delete them, then disconnect the battery. Leave disconnected for several minutes to be sure, but doing that will cause LTFTs to be lost, so when you restart, the ECM will begin building new FTs based on the current conditions. If you do that and get 171/174 again after some driving then, you haven't yet arrived at the lean issue.

 

Thank you very much for the detailed response! I bought the car as it sits with Hurricane CAI, Pfadt headers, Borla mid pipe and catback. The car was tuned in California. The lean codes can take a week of driving to reappear after clearing. When I swapped in my Blackwing, they would reappear same day. I am pretty sure my buddy can fix this in the tune. Car runs awesome. It has 19k miles and it is very obvious it has not been tracked or abused. I do wonder slightly about an exhaust leak. I tightened clamps near front O2's. I need to grab a better scanner with live data.

 

If it takes a week of driving to produce the lean codes, they're not caused by a manifold vacuum leak like a port open. You have a tune problem.

 

Thank you, that is what I have suspected all along so hopefully my tuner will fix it properly. Thanks again for your help....

 

‘08 that came from Bowling Green with the same codes being thrown from the start. Engineers had me do two things 1) tape off holes and seams around air intake and front fascia and 2) change fuel type to Chevron (don’t laugh). Turns out the MAF sensor was extremely sensitive to turbulence that the resulting airflow pattern from the “leaks” caused. As for the fuel, no impact on CEL’s but fuel pump hasn’t failed yet!

 

I do try to use Shell or Chevron, and I run Techron cleaner as well. I think the TSB you are referring to is if you have the stock air intake?

 

I also just changed the MAF to the updated part number with letter and number vs just a letter.

 

I never knew anyone who spent a fair chunk on mods, that didn't run the H out of it only once or twice.

BTW, if you haven't heard, the heads may give you $$$$$ problems. Keep a close eye or ear on it.

 

Without a doubt, I agree with you these cars are fun bone stock. I drive them and have fun myself, but don't abuse them. I keep my clutch fluid perfect and so forth. Yes my last 08 had the heads done. This motor sounds so good, and smooth but you never know for certain. I'm sure there is a lot more risk if one is tracking and racing an LS7.

 

Never saw a TSB on the bumper holes and fascia seams but yes, stock air intake. Key take away was the sensitivity of the MAF which your tuner should be able to address.