P0171/4 After a bunch of work
Thread Starter
Registered User
Joined: Apr 2013
Posts: 7
Likes: 0
P0171/4 After a bunch of work Hi all,
Just got done a winter (and spring I guess) project. I have a 2000 C5 Coupe M6, 103,000 mi, which already had ARH LTs and Vararam, and was running good. Now it's got 2002 Z06 Heads + Cam + Intake + TB + Injectors, new OEM valvetrain parts, and U/D pulley. I also got a mail order tune from a reputable tuner, based on an Z06 with the same bolt-ons.
Startup went fine mechanically, but it was very rough idling. The car was driveable, and idle smoothed out as well, but soon started throwing P0171 & P0174 at the same time. I have Torque and an OBDII scanner...I cleared the codes a few times but they keep coming back, and I've only put about 35 miles on the car now. I am seeing very high fuel trim values, like this:
LTFT1/2 : pegged at 25 in all conditions
STFT1/2 : At a hot idle, creeps up to 40%; at cruise/low load, 10-15%; about the same at higher load. Sometimes spikes to 20%.
I tried a couple things, none of which fixed anything...MAF cleaner, re-torqued intake manifold...I had damaged my EVAP line clamps during the job and replaced that today with a fuel hose...I've checked every PCV hose I can put my hands on (which isn't all of them). Nothing obvious.
I am content to keep looking, as there might be something lurking behind the intake (it's kind of a mess back there), but I'm wondering if some of you all with tuning experience can answer a few questions:
Thanks for any answers or tips. I've got some ideas but I'm not sure where to start on this right now.
Just got done a winter (and spring I guess) project. I have a 2000 C5 Coupe M6, 103,000 mi, which already had ARH LTs and Vararam, and was running good. Now it's got 2002 Z06 Heads + Cam + Intake + TB + Injectors, new OEM valvetrain parts, and U/D pulley. I also got a mail order tune from a reputable tuner, based on an Z06 with the same bolt-ons.
Startup went fine mechanically, but it was very rough idling. The car was driveable, and idle smoothed out as well, but soon started throwing P0171 & P0174 at the same time. I have Torque and an OBDII scanner...I cleared the codes a few times but they keep coming back, and I've only put about 35 miles on the car now. I am seeing very high fuel trim values, like this:
LTFT1/2 : pegged at 25 in all conditions
STFT1/2 : At a hot idle, creeps up to 40%; at cruise/low load, 10-15%; about the same at higher load. Sometimes spikes to 20%.
I tried a couple things, none of which fixed anything...MAF cleaner, re-torqued intake manifold...I had damaged my EVAP line clamps during the job and replaced that today with a fuel hose...I've checked every PCV hose I can put my hands on (which isn't all of them). Nothing obvious.
I am content to keep looking, as there might be something lurking behind the intake (it's kind of a mess back there), but I'm wondering if some of you all with tuning experience can answer a few questions:
- Given this is just an upgrade from LS1 to LS6 specs (+ bolt ons), is this much fuel trim even possible from a tuning problem? It's possible that there was some miscommunication when I ordered it. I don't know much about tuning but it would seem like unless he tuned it as a Geo Metro, even a bone-stock LS1 tune wouldn't be this far off.
- One thing I'm worried I haven't done right, and its hard to see, is the dipstick install. It is in and seems to give a sane reading, but it didn't quite meet the header mount like I thought it should. Is it possible for a loose dipstick to cause this much of a problem?
- I installed EGR/AIR, even though I'm pretty sure the LS6 doesn't have it. It feeds into the Vararam, I figured it couldn't hurt. Am I wrong?
- I tried the old trick of yanking off a hose to see if things got worse. This was the PCV hose on the passenger side of the TB. Didn't seem to change much. Is this confirmation I have a major leak somewhere?
- Any way other than battery d/c to reset LTFTs? Might be useful to see what is going on without the computer trimming around it.
Thanks for any answers or tips. I've got some ideas but I'm not sure where to start on this right now.
Thread Starter
Registered User
Joined: Apr 2013
Posts: 7
Likes: 0
I did not; I removed the casting fins from the intake. Do you think the h-pipe might be lifting the intake anyway?
I decided on modding the intake because I wanted to keep the crossover function, arguments for it were good...but obviously if it's breaking the car I will spend the few bucks for the LS6 pipe/plugs.
EDIT: Just ordered them. I think I am going to be pulling the intake anyway to check for leaks. I'd rather rule out this possibility then get any kind of small advantage from more crossover flow.
I decided on modding the intake because I wanted to keep the crossover function, arguments for it were good...but obviously if it's breaking the car I will spend the few bucks for the LS6 pipe/plugs.
EDIT: Just ordered them. I think I am going to be pulling the intake anyway to check for leaks. I'd rather rule out this possibility then get any kind of small advantage from more crossover flow.
Last edited by kernelPanicked; Apr 29, 2013 at 10:06 AM.
The green plastic clips that hold the knock sensor wires to the crossover pipe need to be removed too. I won't get into the argument that the small amount of coolant that flows through that pipe can have much if any effect on cylinder head temps.
Thread Starter
Registered User
Joined: Apr 2013
Posts: 7
Likes: 0
Yeah let's not touch that one. 
I like not spending money, and it was a supposed (small) advantage, so I went with it. I did remove the green clips as well.
Any opinions on the magnitude of the trim? Can we say definitely that something is leaking/broken, or could this big of a problem result from just from an inaccuracy in the tune?
I like not spending money, and it was a supposed (small) advantage, so I went with it. I did remove the green clips as well.Any opinions on the magnitude of the trim? Can we say definitely that something is leaking/broken, or could this big of a problem result from just from an inaccuracy in the tune?
Thread Starter
Registered User
Joined: Apr 2013
Posts: 7
Likes: 0
Just thought I'd ask, I don't really know what the differences in tune would be given the relatively minor mods (no cam/FI). If there was miscommunication about the tune, it would have been about injector poundage, EGR, or something like that...which I would have expected to lead to minor fuel trims, at least not enough to throw these codes. Your answer tells me there's nothing definitive about this amount of LTFT to say "tune's fine, your motor's broke".
Sorry to ask a stupid question, but I at least try not to ask it more than once.
Thanks for the help, sounds like the best thing to do is just pull the intake, fit the LS6 coolant tubes, and check everything else (PCV, etc) out.
Sorry to ask a stupid question, but I at least try not to ask it more than once.
Thanks for the help, sounds like the best thing to do is just pull the intake, fit the LS6 coolant tubes, and check everything else (PCV, etc) out.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
I agree with 2xLS1, without seeing the tune (if the tuner will allow you to post it, Im not sure of LS1Tech's policy) it's very difficult to say what's wrong. To me, sounds like it needs to be tuned again, if your LTFTs are maxxed out at 25 and STFTs are very positive, the tune isnt delivering enough fuel (or even close to it).
Thread Starter
Registered User
Joined: Apr 2013
Posts: 7
Likes: 0
I agree with 2xLS1, without seeing the tune (if the tuner will allow you to post it, Im not sure of LS1Tech's policy) it's very difficult to say what's wrong. To me, sounds like it needs to be tuned again, if your LTFTs are maxxed out at 25 and STFTs are very positive, the tune isnt delivering enough fuel (or even close to it).
