Onyx Z

iTrader: (3)

My car's been throwing two lean codes, one on bank one and the other on bank two. I've replaced the front 02's, had the codes deleted for the rears, cleaned the MAF, and checked for apparent vacuum leaks. The MAF is ported, but everything has been fine until now; it has been ported for about 10 months, so I don't see why it would do this now? Whenever I cleaned the MAF, it ran fine for a day, then the light came back on. The same thing happened when I changed the 02's. It still runs like normal, just the lights on and it's running lean for some reason. Are there fuel pressure regulators on LS1's, if so, I've never heard of them having one and where would it be? What else could it be? Clogged injector, bad MAF, etc? Any help is appreciated.

Thanks
Ryan

felton316

You might have a vacuum leak somewhere after the MAF, so unmetered air is sneaking into the system. That would throw everything off towards the lean side.

Onyx Z

iTrader: (3)

I knew a vacuum leak after the MAF would cause a lean condition. I am positive it is not this.

Ryan

NightHawk

iTrader: (1)

ttt for ya, I'm having the same problem. Car runs fine, but is constantly lean. Throws a P0171 and P0174, with LTFTs in the 25 range...usually sets the code at low throttle/engine load (1% or 2% load). I thought it was my ported MAF, so I bought an SLP MAF but the problem is the same. I was just about to change the front O2s next. Out of curiosity, what bellows do you have? I have the fernco and I'm thinking about going back to stock just to see if that has any effect

Texas Terminator

got headers? if so, you could have a leak at your collectors. how old is your fuel filter?

Onyx Z

iTrader: (3)

Nighthawk, I was throwing the same codes as you and my light just went off when I was driving down the road. I'm pretty sure it was an exhaust leak. I have the fernco bellows. Check the exhaust for leaks.

Yes I do have headers, like I said above, the light went out while I was driving down the road. I knew an exhaust leak would throw off the 02 readings, but I didn't know if it would read rich or lean, guess it's lean.

Ryan

NightHawk

iTrader: (1)

yeah, mine was doing that too, then it would come back on seemingly at random


I can't speak for Onyx, but my fuel filter is new and I'm getting a consistent 60 psi at the schrader valve. I have the stock manifolds and cats, then duals after the cats. The only exhaust issue that I think I could have is the AIR tubes. I took them off to change plugs and didn't have any new gaskets, so I seated them back on as well as I could and tightened the **** out of them. Got new gaskets coming in on Monday, hopefully that will help out.

Onyx, is your light staying on, or is it going off then coming back after a little bit?

Onyx Z

iTrader: (3)

It just came back on today, but I know I have a bad exhaust leak, so that's probably what the problem is. It will probabaly go off in a couple of days, then come back on.

Ryan

Onyx Z

iTrader: (3)

Ok, I fixed the exhaust leak and replaced the 02 sensors. The light came back on after about 20-30 miles. WTF could it be? Could a very, very small exhaust leak cause this? No vacuum leaks and I just cleaned the MAF.

Ryan

VoodooWS6

A great method for checking vacuum leaks is to take a propain torch (not lit!) ..just the gas on with the car running and if there is a leak, the car will idle down to almost nothing. You can then pin point where the leak is comming from..

I had a little honda for a winter beater, and it had like 2000 vacuum lines on it! Worked good!

NoGo

iTrader: (2)

What was the last thing that you did before it started throwing this code??

NightHawk

iTrader: (1)

I soooo feel your pain

I put in new AIR gaskets thinking that the leak there was causing the problem. The light went off by itself almost immediately, then later that day it came back on

ttt for ya

Onyx Z

iTrader: (3)

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This has been going on for about 2 weeks now, but if I remember correctly, I didn't do anything that would throw a code, except for drive it. Why do you ask? Have an idea?

Ryan

NoGo

iTrader: (2)

There are alot of things that can cause the car to start throwing lean codes. Usually the last 'mod' that was done to the car causes this code to be thrown in some round-about way that the owner/installer is not aware of.

Stuff that will cause your car to throw lean codes:

Section 1: LTerms are High On One Side Only

1) Vacuum leak: If your LTerms only go high when the car is at little to no throttle, then the chances are 99.999999% that you have a vacuum leak.

2) Exhaust leak: Typically, this will only cause one side to throw a lean code. If both sides are throwing a lean code, then you should start looking at the items on your car that control the overall fueling.

3) Bad O2 sensor: A dirty or 'blind' O2 sensor (from running leaded gas etc...) will percieve a lean condition.

4) O2 Connection: Improper power to the O2 sensor (ground or whatever) will percieve a lean condition.

5) Cutout too close to O2 sensor, or open headers: The reversion in the exhaust system exposes the O2 sensor to too much oxygen causing a lean condition to be seen.

6) Bad Injector: A faulty injector will cause the LTerms on one bank to go high. The lean condition will be intermittent and LTerms will typically be higher at lower throttle conditions.

7) Misfire, One Bank: The unburned oxygen leaving the bad cylinder causes the O2 sensor to percieve a lean condition.

8) Coolant In Combustion: If you have coolant exiting the cylinder it will cause the O2 sensor on that bank to percieve a lean condition.

9) Long Tubes: Cold conditions in combination with some long tube headers excessively cool the oxygen sensors. If the oxygen sensor cannot get up to operating temperature it will falsly report a/f to the lean side. This is typically seen during the winter at low RPM freeway driving.


Section 2: Both Banks Showing Lean - LTerms High on Both Sides

1) MAF: If your MAF is not clean or is not reporting a/f properly it will upset fueling on the lean side causing both banks to throw a lean code.

2) Fuel Pressure: If your fuel pressure is too low for your current program (plugged filter etc...) fueling will be inadequate for all operating ranges and your vehicle will run lean.

3) Big Cam: Exceptionally large cams will generate too much reversion in the exhaust (and intake) causing the fueling to be upset by both the MAF and the O2 sensors at lower RPMs

4) Big Exhaust - Long Tubes: If your exhaust is too large, or moves the O2 sensor too far away from the engine, the O2 sensors cannot get up to operating temperature and will falsely report the a/f ratio lean.

Vacuum Leak: A large vacuum leak will cause the motor to run lean on both banks.

Leaded Gas: Running leaded gas destroys the O2 sensors with a couple miles. The lead plugs the oxygens sensors making them percieve a lean condition.

Multiple Misfires (Both Banks): The excess, uncombusted air leaving the cylinders causes the O2 sensors to percieve a lean condition.

Poor Tune: A poor tune made to the MAF table, Injector Flow Rate Table, Injector Offset table, can cause your car to run lean.

Rail Voltage or Wrong Injectors: If your car is having voltage problem, the inadequate power causes the injectors to fuel improperly and late causing a lean condition and poor running.


Thats all I can think of right now. If somebody would like to add one to the list or make a correction please let me know.

Onyx Z

iTrader: (3)

I just checked the codes again. They are as follows: P0171 and P0174. If I remember correctly, they were bank 1 and 2 fuel trims lean.


Ryan

Kurt D

iTrader: (2)

We just had this problem with my friends car. He has longtubes and a ported MAF. We found a vacuum leak around the EGR hose (just out of the blue, never touched it before), this caused the "lean condition" SES. The second problem was +25 LTerms, we replace the ported MAF ends with stock descreened ones. So far so good now.

Onyx Z

iTrader: (3)

Well, I have no EGR, so that's out. As for the ported MAF, mine has been fine for almost a year.

Kurt D, was his problem intermitent?

Ryan

onehardmaro

Check your fuel pressure and injectors yet?

Onyx Z

iTrader: (3)

What should the fuel pressure be at? 58psi correct? And is there a way to check the injectors? I never thought so, other than listening to them.

Ryan

onehardmaro

Lift the fuel rail(injectors will be connected) and turn the key to the on posistion(dont try to start). Each of the injectors will pump once, leaving a little gas under each injector. The one without a spot of gas or the one leaking gas is causing the problem. I thinks its only four bolts holding the rail on to the intake.