let us talk about MAFs baby..lets talk about MAFs

**shady milkman** · 05-27-2009, 09:45 AM

hey guys want to pick your brains for a little bit

i have been having a intermitent lean on both banks and a high idle DTC codes for the past month to two months........

now i highly doubt its a vacuum leak anymore since its become so intermittent...i am starting to think its a maf issue...

1)so i had a vacuum leak about 2 mounths ago after my ls6 intake install...got it fixed

2) got my pcm tuned by frost(great job by the way) and when i plugged it in..the ses light immediately came on..

3)got the code read and it was a throttle positioning sensor error..got it cleared and it came back...so i replaced it..and it went away..so i drove SES free for around 100-200 miles

4)SES light came on with lean on bank 1, lean on bank 2, and a high idle dtc

5) now the light comes on some times for a 10-100 miles then off for 10-100 miles if not more.

here is were it gets weird

when the light is off..the car idles bad..sputters and idle is iradic(sp) ..from 400-900ish ..and will usually idle jumping between 600-800...giving it a reving sound that is quite annoying...
pumping on the brakes does not change the idle and smoke aqnd spray tests do not show anything

when the light is on however..the car runs better ..the idle is not surging so much...however my top end suffers

so i cleaned my maf..and realized that the maf sensors were dirty..covered with kn filter oil..so i cleaned them very carefully and no change

so here is what i am wondering...when MAFs start to fail...do they read low ?? meaning do they tell the pcm that the amount of air is actually lower then what it really is..then ..as the rear o2s see how much air is being passed..they see that it is much more then the amount of air the maf was reading..tricking the pcm into thinking its running lean...

now stick with me...if the maf is reading low and handles the fueling..it thinks less air is coming in then what really is..so the amount of fuel would also be lower...so when the O2s see more air then expected..it reports and the pcm starts to dump more fuel in to "balance the A/F" soo when its dumping fuel..it is actually getting a better a/f ratio ..for the TRUE amount of air coming in..so the car runs better while reporting lean on both banks....but now when the SES light goes off and the pcm no longer fuels like the system is lean...the system is not getting enough fuel for the amount of air..and its actually causing a lean condition ..and the bad idle/sputtering ..while not tripping the SES for lean

or simply it is the iac that could be stuck open allowing too much air to come in for idle ........

both the maf and the iac have been cleaned..the iac is spotless and the maf is now

soooo what do you guys think?

**Dr.Crash** · 05-27-2009, 10:06 AM

Do you have a friend who would let you try his MAF? Do you know anyone with HP tuners that could scan your car and get a log while running? That sounds really strange

**pajeff02** · 05-27-2009, 10:08 AM

Gremlins!

What you are saying makes sense. Do you have access to another MAF to change it out? You can also disconnect your air inlet and partially block your MAF opening with your hand to see what happens. This would reduce the air entering your engine and might give you an idea on whether or not this is an issue. Also, wouldn't hurt to change out your fuel filter and check your pressure at the rail since the SES is indicating a lean condition.

**shady milkman** · 05-27-2009, 12:38 PM

Originally Posted by Dr.Crash

Do you have a friend who would let you try his MAF? Do you know anyone with HP tuners that could scan your car and get a log while running? That sounds really strange

hmm i will see hi-po this weekend ..i am sure he will let me run his maf

..and he also has hp tuners

**shady milkman** · 05-27-2009, 12:41 PM

Originally Posted by pajeff02

Gremlins!

What you are saying makes sense. Do you have access to another MAF to change it out? You can also disconnect your air inlet and partially block your MAF opening with your hand to see what happens. This would reduce the air entering your engine and might give you an idea on whether or not this is an issue. Also, wouldn't hurt to change out your fuel filter and check your pressure at the rail since the SES is indicating a lean condition.

wont every car react when you change its airflow ...but yea i should check the fuel pressure ..but the high idle is what confuses me..its why i think its a issue of the non proper measurement of air in the system..and with it being sporadic it points me to senor failing then a mechanical issue ..but i will check the fuel pressure to the rail and swap out my fuel filter

**Dr.Crash** · 05-27-2009, 12:44 PM

Originally Posted by shady milkman

hmm i will see hi-po this weekend ..i am sure he will let me run his maf

..and he also has hp tuners

ya well since hi car is moving, i dont think he will mind.

maybe it is the IAC sensor. i hatewhen problems are intermintant

**shady milkman** · 05-27-2009, 12:46 PM

Originally Posted by Dr.Crash

ya well since hi car is moving, i dont think he will mind.

maybe it is the IAC sensor. i hatewhen problems are intermintant

those little shits are 80-100 bucks

**Dr.Crash** · 05-27-2009, 12:54 PM

Originally Posted by shady milkman

those little shits are 80-100 bucks

just use hi-po's

**shady milkman** · 05-27-2009, 12:56 PM

Originally Posted by Dr.Crash

just use hi-po's

oh mafs..are 150..but those iacs are 80-100..but yea i will just trade him when he isnt looking..i am sure at the show he will have his hood up..yank! got myself new sensors

**Dr.Crash** · 05-27-2009, 12:57 PM

5 finger discount. so this all started after the intake swap?

**shady milkman** · 05-27-2009, 01:00 PM

Originally Posted by Dr.Crash

5 finger discount. so this all started after the intake swap?

i think just bad timing really ..i broke the seal of the engine..and then the vacuum leak...torn pcv hose and the rear gasket wasnt sealing right ..and the fitting on the back issue...but then ..i would guess with how often we had the air tract off something might have bothered the maf or something....its no biggy ..its a 11 year old car..shit breaks

**Dr.Crash** · 05-27-2009, 01:02 PM

Originally Posted by shady milkman

i think just bad timing really ..i broke the seal of the engine..and then the vacuum leak...torn pcv hose and the rear gasket wasnt sealing right ..and the fitting on the back issue...but then ..i would guess with how often we had the air tract off something might have bothered the maf or something....its no biggy ..its a 11 year old car..shit breaks

Stuff like this always seems to happen together. Thats why im glad i went with an SD tune. takes one more piece of GM junk out of the equation. what about injectors? maybe dirty

**Cutlass** · 05-27-2009, 02:25 PM

If ya just had a scan tool to read the PCM data you would have had this thing figured out 2 months ago!!

Instead we are playing guessy games

**Too Fast** · 05-27-2009, 02:30 PM

My bet is on an unfound vacuum leak.

**shady milkman** · 05-27-2009, 02:37 PM

Originally Posted by Too Fast

My bet is on an unfound vacuum leak.

at random intervals ?

**shady milkman** · 05-27-2009, 02:38 PM

Originally Posted by Cutlass

If ya just had a scan tool to read the PCM data you would have had this thing figured out 2 months ago!!

Instead we are playing guessy games

this is true

**Too Fast** · 05-27-2009, 02:47 PM

Originally Posted by shady milkman

at random intervals ?

Yup. 10-100 miles really isn't random. Could be a flopping/weak vacuum hose, or a barely-sealing/slipped intake manifold gasket. Or a not-quite fitting bellows around/behind the MAF. This all happened after the new intake, right? That's the first place to check, any and all areas around the install. When I have to check someone's work, that is always the first thing to do: go over the area with a fine tooth comb, so to speak, and usually the problem is there. Good luck!

**shady milkman** · 05-27-2009, 07:31 PM

Originally Posted by Too Fast

Yup. 10-100 miles really isn't random. Could be a flopping/weak vacuum hose, or a barely-sealing/slipped intake manifold gasket. Or a not-quite fitting bellows around/behind the MAF. This all happened after the new intake, right? That's the first place to check, any and all areas around the install. When I have to check someone's work, that is always the first thing to do: go over the area with a fine tooth comb, so to speak, and usually the problem is there. Good luck!

thanks i need the luck...it used to be constantly on ...then i fixed a few things and then it went away..all vacuum lines are secure..gaskets are new and sealed good..i would guess. and bellows is fitted fine and no holes

**0rion** · 05-27-2009, 07:57 PM

high idle is usually an indicator that unmetered air is getting in there. The fact that this started right after your intake install really is suspicious of a leak somewhere. Something not sealing up correctly or something. It *could* be your maf but my gut would say to look elsewhere. The codes it's throwing would be a little help too. Do you still have your LS1 intake laying around? Just for shits and giggles I might be tempted to throw it back on and see what happens no more than it takes to swap an intake. Was your ls6 intake used? What did the rear map sensor look like? Just another spot air could be getting through. Gaskets? I think you're going to have to go over everything with a fine toothed comb to find it. Don't rule the maf out but don't put all of your eggs in that basket either.

**Y2KPewterSS** · 05-27-2009, 09:02 PM

I agree with everything Orion stated, I would swap out a MAF from another LS1 and see if that changes anything. You might be able to eliminate the MAF as the issue that way. Did you buy your LS6 intake used, I am guessing you most likely did. Did you inspect it real good to make sure it doesnt have a crack or damage somewhere?