for the past 6 months or so i've been setting off what appears to be an intermitent lean condition.

the SES will turn on, sometimes even flash for several seconds. then generally after 3 starts it turns off (which means the condition is gone).

the car never stumbles or stalls and has always gotten reasonable gas mileage around town.

up untill recently i've been unable to scan it.

the last time the SES was on it was P0171 which is bank one. i figured the 02 sensor was going bad, but figured i'd see what happened after it turned off and then came back...seeing if it reappeared on Bank 1.

well this time when i scanned it it showed p0171 as expected, and p0174 which is the same code for bank 2.

looking at the LT fuel trims they appear to be right around 25%, which if i'm not mistaken is pretty freakin high.

note:
o2 sensors were replaced after flooding in wilma...in oct of 05. and have maybe 5K miles on them.

NOW....

could ethanol be doing this to the car?

could a dirty MAF be causing it? i have a k&n and havn't cleaned the maf in 5yrs.



i plan to look over the vacumn lines to see if that's the problem.



any other suggestions??

the intermitent part of it is what has me baffled.

by the way i drive 7 miles each way to work...generally 2-3 times a week...that's about it.
taken it on several 50...100...150 mile trips in the past months with no SES issues on some, but it shows on others.

grrrr.....

 

Clean your MAF that is what commonly causes a code in both banks.

 

cleared the codes, cleaned the maf

no light on the trip to work this AM

we'll see what happens.

but other times i've cleared the code, or let it clear itself...it would run for a week or 2 without the SES coming on. then BAM....then it would go out.

really annoying.

 

Well how dirty was the MAF?

 

i guess i'm not sure what constitutes "dirty"

it was dark colored. electronics cleaner and a q-tip got alot of it off.

the q-tip was a dark grey by the end.

i wouldn't say it was gummed up real bad though.


i've had a suggestion that it could be an intake leak. however the intake has been on for 3.5yrs...and this problem has started in the past 6 months.

 

Lean codes on LS1s are almost always caused from a vacuum leak in the PCV system. The only other common cause is a contaminated MAF. And you should NEVER, EVER clean the MAF with a Q-tip. No contact should ever be made with the sensing element. A light spray of electronics or MAF cleaner does the trick.

A flashing SES light means the PCM is currently detecting a constant misfire.

 

i know the flashing SES shows misfire. but while it is flashing the car runs fine. even at idle and under load.

the q-tip never touched the sensors...just the bars they're conected to.

i was very carefull.

i'll check the PVC system....where would i look to find common leaks?

 

Check the hose from the PCV valve itself all the way back behind the intake and to the valve cover. The hose deteriorates and gets really soft, sometimes tearing open. You may not see it or hear it. Best way to tell is to remove it and thoroughly inspect.

 

I agree, it might be the IAT sensor going bad.

SteveC

 

Personally, I never had good luck cleaning my MAF sensors in any of my cars.

The tuner told me to clean if before bringing it in for the dyno tune. Got MAF clearner, sprayed the **** outta it. Repeated after it dried. Looked ok. Brought the car to the tuner, got it on the dyno - MAF = dead.

I never noticed any considerably bad performance, nor did I have any codes, but after they put a new MAF sensor in and finished the tune, the responsiveness was 100% better.

Not saying this is what your problem is, just some perspective.

 

And if you're looking for better numbers you might as well upgrade to to an 85 mm SLP MAF which is 90 cfm more than stock.

 

That would not be a good idea. That MAF has a reputation for causing all sorts of problems. If he needed a larger MAF, which with his engine setup is not the case, then a GM truck or Z06 MAF would work well, but only if the MAF tables have been adjusted for the larger MAF.

 

Agreed. If the stock MAF sensor is seriously becoming a limiting factor it's time for you to go SD. I don't like any of the aftermarket MAF sensors. Speed Density is the way to go if you are that extreme...

But you are not there yet...

 

Yea that is a terrible idea.

Stock MAF is good into serious horsepower. Aftermarket/larger MAFs contribute no substantiated power gains, and often lead to tuning problems.

 

4 trips to work (7miles one way) and one trip to the next town...40 miles one way...

no SES codes

still havn't gotten a chance to drag the computer out to check the LTFTs

don't plan to upgrade the maf anytime soon, i figure the GMS ends are enough for the engine now.

still planning to check out the PVC hoses