Help - I'm getting lean codes after LT install
Thread Starter
Racer
Joined: Jan 2005
Posts: 283
Likes: 2
From: Troy MI
Help - I'm getting lean codes after LT install
Installed FLP long tube headers with high flow cats. All 4 O2 sensors are connected. Also have a Haltech Stinger Intake.
Engine Light is now coming on and getting lean codes P0171 and P0174. Both are shown as history codes.
How can I fix this? Any ideas as to why I am getting these codes?
Your help is appreciated.
Engine Light is now coming on and getting lean codes P0171 and P0174. Both are shown as history codes.
How can I fix this? Any ideas as to why I am getting these codes?
Your help is appreciated.
Burning Brakes
Joined: May 2003
Posts: 1,058
Likes: 0
From: Roswell New Mexico
St. Jude Donor '07-'08
you shouldn't get lean codes from a header install. I have heard a lot of people say they will lean out the car, but after 10-15 header installs on the f-body and y-body i have never had one throw a lean code just becasuse the efficency. First thing i would check is to make sure there are no exhaust leaks before the 1st set of sensors. If you have a leak, air gets the system causing it to think the car is lean.
Check for leaks before you spend the money on tuning
Check for leaks before you spend the money on tuning
Team Owner
Joined: May 2003
Posts: 23,480
Likes: 9
From: East Meadow NY
St. Jude Donor '12
Originally Posted by 2GOFAST
I'll reset the PCM codes now. I'll check for exhaust leaks tonight.
Anymore suggestions?
Anymore suggestions?
Chris
Intermediate
Joined: Oct 2005
Posts: 47
Likes: 0
Well, I'm a total newbie to the Corvette (just got my first one last week! 
) but I used to build hot rods in my youth. If you don't change the fuel schedule, of course you'll get a lean condition. That's kind of the point. You want to pump as much air as possible. With a more efficient exhaust and intake, you pump more air. So if the fuel is the same, you go lean. Obviously the Corvette's computer will try to compensate when in closed loop, but if it's anything like the LT1 computer, it can only go so far. Also, when you hammer it, the computer goes out of closed loop and meters fuel from a chart. I vote for the PCM tune.
Now, if you're getting the codes when just putting around town, well, obviously you have a leak. But if you get them when hammering the gas, then it's reprogram time. Also, I belive it takes a few minutes to go into closed loop (engine warm up), so you're going off the map sensor, tps, and a chart stored in the computer. Again, that could be too lean (but I doubt it). As a former hack with LT1 Edit, I can tell you there's lots of stuff in the GM fuel injection code that can make a car go lean.
Of course, I have zero LS1 experience, so I might be off my rocker.
) but I used to build hot rods in my youth. If you don't change the fuel schedule, of course you'll get a lean condition. That's kind of the point. You want to pump as much air as possible. With a more efficient exhaust and intake, you pump more air. So if the fuel is the same, you go lean. Obviously the Corvette's computer will try to compensate when in closed loop, but if it's anything like the LT1 computer, it can only go so far. Also, when you hammer it, the computer goes out of closed loop and meters fuel from a chart. I vote for the PCM tune.Now, if you're getting the codes when just putting around town, well, obviously you have a leak. But if you get them when hammering the gas, then it's reprogram time. Also, I belive it takes a few minutes to go into closed loop (engine warm up), so you're going off the map sensor, tps, and a chart stored in the computer. Again, that could be too lean (but I doubt it). As a former hack with LT1 Edit, I can tell you there's lots of stuff in the GM fuel injection code that can make a car go lean.
Of course, I have zero LS1 experience, so I might be off my rocker.
Last edited by c131frdave; Oct 14, 2005 at 11:07 AM.
Racer
Joined: May 2001
Posts: 304
Likes: 0
From: Bryn Mawr PA
I installed Kooks LT, an LS6 manifold and a mild cam recently. Left the rest of exhaust stock (Have an x-pipe). According to before and after mods A-Tap shows LTFT changed only a tiny bit (less than a half a point) so I doubt the headers themselves are causing the codes......(This assumes you were failrly close before the mods)
Just my .02 cent though
Just my .02 cent though
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Thread Starter
Racer
Joined: Jan 2005
Posts: 283
Likes: 2
From: Troy MI
FYI - I have reset the codes and they have not reappeared - yet (only taken 3 shorts trips of less than 3 miles each). The codes and engine light have only happened when I drive the car for an extended distance/time (such as more than 5 miles). Also, I have been using WOT at times.
I appreciate all of the comments/thoughts and suggestions - keep them coming.
I will be putting on some after market mufflers soon - so i think if a tune is needed I should wait until the new mufflers are on the car. Is there a problem waiting for the tune (assuming the lean condition reoccurs)? I certainly don't want to cause damage.
thanks
I appreciate all of the comments/thoughts and suggestions - keep them coming.
I will be putting on some after market mufflers soon - so i think if a tune is needed I should wait until the new mufflers are on the car. Is there a problem waiting for the tune (assuming the lean condition reoccurs)? I certainly don't want to cause damage.
thanks
Racer
Joined: Aug 2001
Posts: 469
Likes: 0
From: Pasadena MD
Originally Posted by Jack Behrle
I installed Kooks LT, an LS6 manifold and a mild cam recently. Left the rest of exhaust stock (Have an x-pipe). According to before and after mods A-Tap shows LTFT changed only a tiny bit (less than a half a point) so I doubt the headers themselves are causing the codes......(This assumes you were failrly close before the mods)
Just my .02 cent though
Just my .02 cent though
Same thing for me ,cept no cam changeHi Jack
Pro
Joined: Aug 2004
Posts: 575
Likes: 0
From: Richmond Hill Ontario
I installed a complet new exhuaust sytem front to back consisting of LT headers, random tech hi-flo cats, X pipe and Z06 Ti mufflers. Not one code was set. Installed a head and cam package afterwards and still did not set any codes. This was all before getting any tuning done. I don't think your codes have anything to do with the headers themselves. You mentioned history codes which means that the problem occurred some time before you installed your headers. History codes indicate a problem has occurred but did not occur enough times or for a long enough time to set a DTC in your display. I'd say you've either got a leak around the header flange or right at the O2 sensor. What kind of gaskets did you use with the headers? Also, based on the age of your car, you might need to replace the O2 sensors. Hope this helps.
Thread Starter
Racer
Joined: Jan 2005
Posts: 283
Likes: 2
From: Troy MI
The car is a 2004 so I doubt the O2 sensors need replaced. I used new gaskets. I used the earlier C5 style with the round openings to match the headers.
The check engine light came on which, i assume, means that the problem happened at that time.
Any more advice or thoughts??
The check engine light came on which, i assume, means that the problem happened at that time.
Any more advice or thoughts??
Pro
Joined: Nov 2003
Posts: 548
Likes: 0
Originally Posted by 2GOFAST
FYI - I have reset the codes and they have not reappeared - yet (only taken 3 shorts trips of less than 3 miles each). The codes and engine light have only happened when I drive the car for an extended distance/time (such as more than 5 miles). Also, I have been using WOT at times.
I appreciate all of the comments/thoughts and suggestions - keep them coming.
I will be putting on some after market mufflers soon - so i think if a tune is needed I should wait until the new mufflers are on the car. Is there a problem waiting for the tune (assuming the lean condition reoccurs)? I certainly don't want to cause damage.
thanks
I appreciate all of the comments/thoughts and suggestions - keep them coming.
I will be putting on some after market mufflers soon - so i think if a tune is needed I should wait until the new mufflers are on the car. Is there a problem waiting for the tune (assuming the lean condition reoccurs)? I certainly don't want to cause damage.
thanks
I had similar codes when I had the long tubes installed. I believe it is the coating inside the headers causing this because the codes became less frequent and then disappeared over a few months.
Thread Starter
Racer
Joined: Jan 2005
Posts: 283
Likes: 2
From: Troy MI
Thanks for all the help.
I reattached my air intake and checked for leaks.
I have not received anymore codes
I'll see what happens today - I am going to a long drive - only a few days left before winter storage
I reattached my air intake and checked for leaks.
I have not received anymore codes
I'll see what happens today - I am going to a long drive - only a few days left before winter storage
