P0171 & p0174
10-08-2014, 07:06 AM
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P0171 & p0174 New engine build with 1k miles on the build so far.
It started throwing the P0171 and P0174 about 4 days ago. I thought it was because I had to take the exhaust off (ran off the road avoiding an accident and it hit the frame, header and exhaust) and now I have open headers, but I usually do that everytime I go to the strip anyway. Normally it makes the engine run rich not lean.
Engine idles fine and stft's look ok at idle and when under heavy throttle. When cruising or light throttle they shoot up. Last time it threw the code STFT's were 56% LTFT's were 26%.
Here's what I've done so far:
1) Cleaned the maf
2) Checked fuel pressure 60 psi at idle 59 psi wot
3) Checked the intake bolts since I put new gaskets on the intake
4) Sprayed carb cleaner on everything with no change in idle
5) Changed the bank 2 o2 sensor since that's the side that got hit
6) Did a pcm relearn (worked for a little while then ft's went back up
7) Checked the vacuum lines that run around the intake and to the brake booster (which are all brand new)
8) Checked all the header bolts and also can't hear any leak around the flanges where the bolt into the head
Like I said it idles fine and at idle the stft's look pretty normal, but under light throttle they shoot up.
Motor info just in case someone needs it.
Mahle forged pistons, blueprinted and balanced, ARP's, stock cam, crank, maf, P/P throttle body, A/C delete, P/S delete, Stock LS6 intake, upgraded oil pump.
I need help. This is my daily driver. I may be able to get my hands on a smoke machine.
I can also watch the readings live.
It started throwing the P0171 and P0174 about 4 days ago. I thought it was because I had to take the exhaust off (ran off the road avoiding an accident and it hit the frame, header and exhaust) and now I have open headers, but I usually do that everytime I go to the strip anyway. Normally it makes the engine run rich not lean.
Engine idles fine and stft's look ok at idle and when under heavy throttle. When cruising or light throttle they shoot up. Last time it threw the code STFT's were 56% LTFT's were 26%.
Here's what I've done so far:
1) Cleaned the maf
2) Checked fuel pressure 60 psi at idle 59 psi wot
3) Checked the intake bolts since I put new gaskets on the intake
4) Sprayed carb cleaner on everything with no change in idle
5) Changed the bank 2 o2 sensor since that's the side that got hit
6) Did a pcm relearn (worked for a little while then ft's went back up
7) Checked the vacuum lines that run around the intake and to the brake booster (which are all brand new)
8) Checked all the header bolts and also can't hear any leak around the flanges where the bolt into the head
Like I said it idles fine and at idle the stft's look pretty normal, but under light throttle they shoot up.
Motor info just in case someone needs it.
Mahle forged pistons, blueprinted and balanced, ARP's, stock cam, crank, maf, P/P throttle body, A/C delete, P/S delete, Stock LS6 intake, upgraded oil pump.
I need help. This is my daily driver. I may be able to get my hands on a smoke machine.
I can also watch the readings live.
10-08-2014, 08:22 AM
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Here is a theory I have going. Since the o2's are at the back of the LT's I think fresh air is getting to the o2's while cruising and making the pcm think the engine is running lean and dumping fuel to try to compensate for it, which is why at idle and wot they fuel trims go back to normal.
As I was scanning it a few minutes ago I got the usual P0171, P0174 and now P0306, which is probably a fouled plug from being pig rich.
Any thoughts on that theory?
As I was scanning it a few minutes ago I got the usual P0171, P0174 and now P0306, which is probably a fouled plug from being pig rich.
Any thoughts on that theory?