robertbartsch

My car has been running ruff for weeks - no codes. Changed plugs, wires, etc, - no help.


Today, however, I got a code - Too lean Bank one. Bank one is DRIVERS side; right?

Is this likely a bad fuel injector? These are stock 99s.

horist

could be a couple things:
1. was any exhaust work recently done? could be an exhaust leak at the head or the collector, this would suck in raw air and cause a false lean code. Tighten the header bolts up

2. Bad Injector -- do you have access to a heat gun? You can check the temps of each primary, if one is significantly lower then that could be the issue. A bad injector should eventually set a code, but I'm not sure how long it takes or what procedure it uses to determine an injector is bad (could be a clogged injector... in which case it is working properly but not enough flow)

If you don't have access to a heat gun, you could try swapping injectors... move all drivers side to passenger side and vice versa... see if the code follows

robertbartsch

I have LT headers and the rear O2s sensors have been turned off by LS1Edit. Would this casue a "lean" code in the Sensor "1" bank? I'll check the header/head bolts on Bank 1.

Is the Bank 1 the driver side?

I thought of switching Bank 1 and Bank 2injectors - good idea.

Thanks...

horist

yup bank 1 is driver side (bank 1 generally refers to the side the #1 cylinder is on, in our case drivers side)

The rear O2s shouldn't have anything to do w/this code, the front O2s can sometimes have problems with Long Tube Headers where they throw an Insufficient switching code, but the long tubes themselves shouldn't cause a lean code unless there's a leak or bad injector

If there's an exhaust leak it should be audible (you could try using the screwdriver test... get a large screwdriver, put it on metal and put your ear on the end, lets you hear what's going on much better and makes it easier to hear an exhaust manifold leak)

robertbartsch

OK how about this?

The last time I replaced front O2s the cable on one side (passenger side I think) was too short. I spliced in an extension. Would this cause a "too lean" code? I'll have to check which side I spliced.

horist

possible... usually better to use an extension or best is to use a corvette rear O2 sensor... however, splicing or extensions in long tubes usually (if there's a problem) will set an insufficient switching (sensor will flatline or barely move) or heater code... I've never seen one set a lean code (lean code means that the PCM believes the sensor is working properly... switching properly... but switching too lean)

Plus if this problem just started, and it's been like that for a while... it's likely not that

z-ya

iTrader: (1)

could also be a intake leak

ninobrn99

iTrader: (8)

an intake leak would cause both banks to be lean. i think its either a header leak whether it be at the flange or at the bung, the splicing could also be the reason.

robertbartsch

Thanks.

So I'll try these:
1. Check electrical ground (Back of driver side head???)
2. Check exhaust header for leak at head or collector
3. Swap O2s left to right
4. Check intake manifold for leak
5. Swap injectors left to right
6. Check fuel rail pressure

Anything else?

SMOKINV8

iTrader: (6)

Make sure you didn't extend the O2 sensor between the sensor and its own harness, you want to extend between the car's harness and the PCM. I've read (no first hand engineering on this) numerous times that there is an air gap in one of the wires for the oxygen sensor that is used for reference oxygen levels. If you cut off that reference oxygen level, that O2 sensor is going to read rich. If the PCM tries to lean it out, its going to lean out the other side as well.

I'd check passenger side O2 first, then check for a header leak on the DS. If you want to eliminate the bad O2 scenario, set your car in open loop and see if the problem persists.

muncie21

iTrader: (14)

Why is this?? I would think it's possible to have a leak on one side (bank) and not another.

horist

I suppose if the leak was right at a intake manifold seal, such that it was only allowing excess air into 1 cylinder this would be the case

but it would have to be a large leak (since a too lean code is set when the PCM can no longer accuretly compensate fuel wise... this means that it's already tried adding 25% fuel to the 1 side and it's still running lean)

plus an intake manifold leak will usually cause the idle to fluctuate wildly since it's a vacuum leak

robertbartsch

No - the idle is smooth. Does this rule out an intake leak? I've pulled the intake several times since 99 and it has the original rubber seals aroung the intake ports.

SMOKINV8

iTrader: (6)

I would certainly move intake leak down on the list.

As Horist said, vacuum leaks usually cause idle problems.

Quinncamaro

I to have recently had this code.

Recently made a few simple mods,

maf, throttle body, cat back, air box and K&N and hypertech tuner (for higher octane fuel),

just after these I got the code for both banks being lean, after advice I removed the TB and all has been ok for a couple of weeks. Today just the bank one code displayed after hard acceleration.

could it be:

oil from the new K&N fouling the maf?
too much air for the fuel going in? Though 25% more fuel by the PCM would surely cure this.

Does this info prompt any ideas to help us?

Im hopeful cos there arent too many people with LS1 experience her in London UK

1hotls1

iTrader: (6)

I've been chasing down the cause of a lean code on bank 2 for a week, but I did have a noticeable miss at cruising speed. It turned out to be a weak coil on #8 and now I have no problems.

jub jub

I just had the same problem. Mine turned out to be injectors. I was getting a delta of 10% between sides especially in cells 3 and 7.