Cadillac CTS-V Forum banner

1 - 9 of 9 Posts

·
Premium Member
Joined
·
3,496 Posts
Discussion Starter #1
For the last 4-6 weeks, I'm been trying to resolve P0171 & P0174 codes but I'm running out of ideas and need some help. I know that typically when both these lean codes show up, unmetered air is entering the system through a common area.. i.e., not bank specific. This past weekend, I found a broken manifold bolt on the drivers side and a leak at the test pipe on the passenger side. I thought I found the smoking gun, fixed it but still no change. It was suggested to me that the O2's may be going bad (not heating up properly) but I replaced them about 20k miles ago and I wouldn't think they would both go bad at the same time and so soon. I have 106k miles on the V.

Symptoms:
Fuel trims on both banks are +25% at idle only. However, when at speed, they fall more into place... in the single digits +/-. I know my tune isn't great but I've been running it for the last 5+ years without a problem and old logs show 4% +/- at idle.

I have 2 logs from yesterday if anyone wants to take a look. 1 is on my way to work (7 miles, stop and go traffic) and the other is on my way home (light traffic, some freeway). Logs are in the Dropbox link below (HPT Version 4.4.4).

Any suggestions/ideas and what to check?

Stuff I checked:
Intake connection (G Force intake)
SC Bypass (holds vacuum) & related vacuum lines
PCV tubes - both valve covers and at the intake
Injector O rings
Lid rubber seal
Catch can connections and hoses
Brake booster & hose
Various lid & snout sensor O rings

Stuff I've Replaced
MAF O ring
Oil cap O ring
Valve cover gaskets & grommets
Valley cover intake
Intake gaskets
Test pipe steel gaskets

Mods:
ZL1 lid with phenolic spacer (thin RTV on the SC side)
Ported Snout w/ 2.5 pulley
Ported TB
G Force 4.5" intake (RTV'd PCV port tube)
BB Test pipes with Felpro steel gaskets, flat flange
ID850 injectors
NorCal SC tank
Catch can
Firecore wires
BR7EF plugs gapped at .030 - about 15k on them
AFX WB

Parts I have on hand
2 new O2s
8 BR7Ef plugs
Extra set of PCV plastic tubes
MAF O rigs
 

·
Registered
Joined
·
2,767 Posts
Hope you get things sorted out over there.

Sent from my SM-N976V using Tapatalk
 

·
Premium Member
Joined
·
3,496 Posts
Discussion Starter #3
Hope you get things sorted out over there.

Sent from my SM-N976V using Tapatalk
Thanks. I just ordered a new MAF... hoping for a hail mary. I hate throwing parts at problems but I'm all out of ideas.

Sent from my SM-G975U using Tapatalk
 

·
Registered
Joined
·
1,676 Posts
Someplace I have a description of how the fuel trim system works. I dimly remember maybe that fuel trims are set based on the delta between what the MAF says and how rich the O2s say the combustion process is. No leaks mean either O2s or MAF, there'd be nothing else...
 

·
Premium Member
Joined
·
3,496 Posts
Discussion Starter #5
Someplace I have a description of how the fuel trim system works. I dimly remember maybe that fuel trims are set based on the delta between what the MAF says and how rich the O2s say the combustion process is. No leaks mean either O2s or MAF, there'd be nothing else...
That's helpful. If you can find that description and post/email it to me, that would be great!

Sent from my SM-G975U using Tapatalk
 

·
Registered
Joined
·
97 Posts
One troubleshooting step is to spray carb cleaner around suspect areas while the car is idling and listen for a change in RPM or idle quality. A leak can suck a small amount of carb cleaner in, adding "fuel".
 

·
Registered
Joined
·
49 Posts
yes, check fuel pressure. it is probably the fuel control unit or the second pump not kicking in. Lastly, the fuse box could be loose, under the hood and that will cause the second pump not to work and you end up with lean codes.
 

·
Premium Member
Joined
·
3,496 Posts
Discussion Starter #9
Just to bring this thread to a close, I found the culprit... the TB to intake coupler was the problem. I couldn't find anything wrong with it and removed/inspected it at least a half a dozen times with no change. After verifying the MAF o-ring seated correctly, I had a silicone coupler on hand and swapped it out of pure desperation. Fired her up and the fuel trims dropped as soon as it went into closed loop. The fuels trims were back to normal on the drive to work this morning.

What a fucking ordeal but in the process, I fixed a broken manifold bolt and a test pipe leak.

Sent from my SM-G975U using Tapatalk
 
1 - 9 of 9 Posts
Top