Faulty MAF sensor ?

Made a big discovery today I got to thinking what you guys have been saying about the system goin SD when the MAF is unplugged.

A little back ground is in order.
93 Camaro LT1 M6 in a 72 Elcamino. Upgraded to a 95 PCM and Bailey's LTCC kit. CAI from the Camaro using a K&N filter in the left front fender pocket in front of the wheel well. BBK 58mm 1000cfm throttle body ported to the manifold.

I have just recently acquired TunerPro V5 and able to log data and see what is going on. I found out this thing is fat all across the board consistently know matter what cell it's in. It will start out at 128 and go south within a couple seconds in that cell. So today I unplugged the MAF and fired it up and watched it transition from open to closed. But this time it didn't crash it went to 138 on both banks with the INT's at 128.

Now your collective thoughts please. MAF needs a recal or you think it's toast It's the original unit that came with the PCM I got as a package. Near as I can tell it's stock, it still has the factory screen on it and no signs of tampering with the bore and probably has about 80,000 miles on it?

MAFs, even with the flow straightening grid, are all very sensitive to intake ducting. GM used the same MAF across probably 10 different applications and every one of them have different calibrations.

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Originally Posted by RobertISaar

MAFs, even with the flow straightening grid, are all very sensitive to intake ducting. GM used the same MAF across probably 10 different applications and every one of them have different calibrations.

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I'll see if I can pull up a stock table and compare it to what is in there then.

So would it be your opinion that it may need to be replaced have you seen one do this when it went bad?

And I am asking as I figure someone has probably seen this same scenario and may have found the fix.

what he means (and i agree) is if your intake ducting is way different from a stock lt1, some recalibration is a good idea for sure; a wideband in open loop with a fixed AFR worked really well for me.

i ended up scaling down on the bottom and up on the top, it maintained a stock-like curve, but ended up kind of tilting it.

with the stock maf table i'm around 12% out on the low end; and that's with a fairly standard intake design that still uses a 90 degree elbow to the throttle body.

might be even more extreme if you just use a straight maf on air filter to throttle body with no bends or anything (in which case the maf table from a ram air LT1 might be a good place to start)

Make sure to do the VE table first when tuning.

Wouldn't hurt to get a can of MAF cleaner and wash it out before starting the MAF tune.

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Originally Posted by steveo

what he means (and i agree) is if your intake ducting is way different from a stock lt1, some recalibration is a good idea for sure; a wideband in open loop with a fixed AFR worked really well for me.

i ended up scaling down on the bottom and up on the top, it maintained a stock-like curve, but ended up kind of tilting it.

with the stock maf table i'm around 12% out on the low end; and that's with a fairly standard intake design that still uses a 90 degree elbow to the throttle body.

might be even more extreme if you just use a straight maf on air filter to throttle body with no bends or anything (in which case the maf table from a ram air LT1 might be a good place to start)

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Steveo
I am running a K&N Cold Air Kit with there plastic elbow coming off a 8 inch cone filter up to the MAF sensor input. From the MAF to the throttle body is stock plumbing.

Eagle
I'll look for the MAF cleaner
I also have a friend here at work that has a 94 Camaro with a running LT1 that is going to let me borrow his MAF just to see if it makes a difference.

Well I'll be
Went out to check the size as suggested by another member and found out that when we did the bailey LTCC instal the sensor got flipped and was in backwards. turned it around the right way and the numbers aren't perfect but a hell of a lot better 114 115 BLM with 125 on both INT.

Something I noticed, when I adjusted the injector pulse constant up from 24.03 to 24.91 that was in the original tune from ZAC it seemed to move the BLM's up to the 115 117 I mentioned above but INT stayed around 125's. I bumped it back down to the earlier value that we calculated with the math to 23.58 and it went back to 108 and INT was down around 109 110 so it definitely didn't like that.

Now my question is

Should I bump the constant up a little more to get to 128 and run with that?

Or go back to the correct value we calculated for 22# injectors on a stock rail pressure and then adjust all of my VE tables to correct the rich condition?

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Originally Posted by beestoys

Or go back to the correct value we calculated for 22# injectors on a stock rail pressure and then adjust all of my VE tables to correct the rich condition?

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This!

well that makes sense, mafs dont like to be backwards!

anyway, dont pay any attention to INT (the integrator). once the integrator feeds BLM a proper average, INT should center itself around 128, because BLM has already done the appropriate corrections, so int doesnt have much work to do.

the only thing i'd watch int for, is if the int is very unstable (jumping up and down 10 or more) after the BLMs settle for a while you have problems (maybe corrcl too strong, or some kind of running issue), and the BLM averages are likely corrupt

why wasn't INT around 128 when your BLMs were @ 108? that's normal too. because; 108 is the MINIMUM blm value, it bottomed out, and it wont correct any further. the int was still working its butt off trying to make a 14.7 AFR, blm had given up.

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Originally Posted by EagleMark

This!

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Noted Eagle then I'll go back in and correct for the right calculated values and run a base line again.

Steveo
I'll reset the BLM's and run it setup as Eagle suggests for a base and let you know what it does. I should have the wideband in by then as well. Just need to wire it up and thinking it's going to tell me the 02's are shot. Remember this thing was running with the VSS disconnected for about a year or so so it was running in cells 16, 17, and 18 only.

ill bet they're fine.

Hoping so
Then I can get to logging and tweaking on this thing finally.