Tonite I disconected my MAF and did a Freeway drive then Logged it with my handheld scanner.


This is what I found out.

My BLMs moved up to 128 for the left and 130 for the right. My integrators were moving between 125 and 133 average. My oxygen sensors appear to be moving up and down with a greater range than before.. and faster too, the max retard I saw was 2* degree of retard while I gunned her to pass another car.


Why is it that as soon as I reconect the MAF sensor my BLM's drop to 115 - 119 and my integrators are about 119 too? Also my Idle develops a slight ramdom miss and I have seen my Timing retard as high as 14* and its common to see 9* retard when passing or during WOT? I am at a loss... Disconec the MAF and the Fuel trim gets better and knock almost disappears... reconnect it and it sucks again!!


I dont see anything wrong with the MAF sensor, all readings are within specs and the computer has never been programed...What gives?? Oh when I disconected the MAF I got the 48 code ofcourse (mass air flow system failure) but then I also got the code 52 Oil temp sensor low....?? I didnt know the LT1 keeps track of oil temp.... or does it?


Anyone have any ideas why the whole fuel trim gets better without the MAF??


Marvin

 

i seem to have the EXACT same symptoms you described, to the letter.

this weekend i'm borrowing a friend's MAF and will find out what my BLM's do



also, don't worry about low oil temperature, f-body LT1's don't have a sensor. i've gotten that DTC a few times but its never thrown a light, just a stored code.

 

Hey Guys!

Be sure and let us know what you find out about the maf.

Thanks Lee!

 

Well, with the info you just gave I'd say your car is running leaner with the MAF than the it does with the VE tables its using when the MAF fails. Your MAF set up is pulling gas with the numbers you posted. The leaner a/f is possibly creating more knock, hence more retard. Why? :dunno: You could adjust your MAF tables so that the blm's stay closer to 128 but they are currently within an operating range the PCM can adjust for. Also remember, all this is based off of feedback from your O2's. Hope that helps.

 

Do a comparison!! Your MAF and your friends MAF. Also, is your friends car been scanned yet? I mean you know fer sure his fuel trims are good? "without a computer re-programing that is." If not it will throw your reading off too.

Here is one thought... in case your friends has re-programmed his computer, you can do the comparison using Both MAF on his car instead... and see what happens. But only if he had to adjust the fuel trims on his car. IF not then either car could be a good test mule...


Marvin

 

Yeah thats one more thing... I figured if the 02's were bad the PCM would be adjusting the fuel trim from both The MAF and VE Tables mode too, but it doesnt do it when its using the Tables. I am gunna check for air leaks past the MAF. Perhaps my Intake elbow is torn and the MAF is detecting less incoming air. Woulnt that tell the computer to use less fuel?? Less air less fuel? I'll go check in a few minutes.


Marvin

 

my o2's are relativly new, maybe 6 months. they went on when the longtubes got installed.


also, my BLM's arn't split... at max they're maybe split by 4

 

he does indeed have a programmed PCM, and his MAF is a z06 MAF. right now his BLM's are split, which wouldn't indicate a MAF problem. his MAF is almost brand new.

i'll do a datamaster log of old MAF, no MAF, and new MAF, and see whats going on.

 

I havent found any air leaks between the MAF and the TB.

The Knock retard is finally gone... I know its fixable if I can only find what the problem is while the MAF is connected.

 

Update Update

With the MAF sensor disconected.

I logged Two WOT runs yesterday. WOW!! I had to abort my first WOT because she never hooked up on first gear. (sweeet) The tail was all over the road so I aborted the Run when she was all the way to 5K RPMs without traction. didnt want to stress the tranny on that 1st to 2nd shift.


On the Second WOT I babyed her off the whole and then Hammered it till just 65mph. I wanted to log the shift from 1st to 2nd gear thats it.


The results....There was no knock retard at all... The Knock sensor count did not increase one mark... 60 counts at the begining and 60 at the end of the run. (thats the way is supposed to be). the BLMs and Integrators are right about 128 give or take one point and the power is all back....


I still havent found any air leak after the MAF sensor... I am removing the rubber elbow and check the donkey dong for possible cracks on it... today.


will keep you posted

Marvin

 

update. I did not find any air leaks past the MAF however while changing the coolant I went ahead and changed the Coolant Temp Sensor. I had a brand new one laying around after I did some tests with it... Now My scanner reads the Temp as 166*F with the new Sensor on... with my old sensor the lowest reading ever was 178*.

I havent done any WOT runs yet but I am gunna reconnect the MAF and see if the new sensor has any effect of the Fuel readings. I have the 160*thermo and with the AC on (fans on) the Coolant temp is pegged at the Thermo opening Temp. So this two sensors are reporting 12*F degrees of temp difference..

Marvin

 

sounds like the typical MAF sensor to me. Instead of reading linear so its rich or lean across the entire range of frequencies, its rich down low and lean up high. is it ported?

 

No its not ported. It has the screen on and just as it came stock from the factory.

Marvin

 

Does the computer tune the fuel it thos when it is un pluged? Cause from what i have seen stock 4th gens run fat. If it stays lean hell ya.

 

Not to intrude your thread but im having some problems...

When I disconnect my MAF while the engine is running, the motor will die... Motor also does not run if you try to start it with the MAF disconnected

Im always getting 7deg of knock retard when i shift into 3rd... Will vibrations cause KR? When I had my gears installed I noticed alot more vibrations at crusing speeds abover 80... vibrations are UNBAREABLE at anything over 90... your eyeballs start vibrating, literally

-Robert