Very odd MAF log

[Aloicious]

Hey guys, take a look at this log of mine, watch the MAF freq starting around frame 4575....what is the concensus on this? faulty MAF? it just drops to zero, and only occasionally comes up for a few frames here and there....

I like running with the MAF this is the first I've ran with it since I had it off in may for doing alot of engine/trans work. I did clean it while it was out so I'm wondering if something happened and its bad now, or if it is likely something else.

[Aloicious]

forgot to post the log

[Aloicious]

nevermind, got it fixed, it was a short or something at the MAF connector, ended up splicing a new connector on, and I went ahead and put a new MAF on too (since the older one was almost 14 years old). working pretty good now, just need to do some tuning on it.

[joecar]

A MAF DTC should have appeared, and I see in your log file it was present.

Which MAF did you get...?

Let us know how tuning the new MAF goes.

[Aloicious]

A MAF DTC should have appeared, and I see in yot log file it was present.

Which MAF did you get...?

Let us know how tuning the new MAF goes.

oh yeah, sorry, it was throwing P0102, and would fail into speed density mode, which is why I didn't notice durring the drive when the MAF started giving problems. guess I forgot to mention that heh.
I did my first log with the new MAF this evening coming to work but havent been able to look over it yet.

I actualy got a "stock" acdelco 98 c1500 MAF from the dealer. I say "stock" becuase the MAF I got, that GM uses now for the 96-99 L31's is way different than the original one that was on there. the original was ~75mm inside diameter, and was made from aluminum, with a 3 pin connector, the replacement from the dealer is plastic, the inside diameter is around 80mm, and it has a 5 pin connector, with a pigtail adapter to mate it to the 3 pin engine harness connector. It appears to be just a newer style MAF with the integrated IAT, I'm sure GM is trying to save money by just manufacturing the same part as a later MAF and including the wiring adapter.

either way, it seems to be working well, though it needs some tuning to bring it into line.

[joecar]

What is the GM part number of it...?

[Aloicious]

What is the GM part number of it...?

I'll have to grab it when I get off work tommorow.

[Aloicious]

What is the GM part number of it...?

looks like its ACDelco pn 19208521

[joecar]

Ok, thanks.

[hog]

oh yeah, sorry, it was throwing P0102, and would fail into speed density mode, which is why I didn't notice durring the drive when the MAF started giving problems. guess I forgot to mention that heh.
I did my first log with the new MAF this evening coming to work but havent been able to look over it yet.

I actualy got a "stock" acdelco 98 c1500 MAF from the dealer. I say "stock" becuase the MAF I got, that GM uses now for the 96-99 L31's is way different than the original one that was on there. the original was ~75mm inside diameter, and was made from aluminum, with a 3 pin connector, the replacement from the dealer is plastic, the inside diameter is around 80mm, and it has a 5 pin connector, with a pigtail adapter to mate it to the 3 pin engine harness connector. It appears to be just a newer style MAF with the integrated IAT, I'm sure GM is trying to save money by just manufacturing the same part as a later MAF and including the wiring adapter.

either way, it seems to be working well, though it needs some tuning to bring it into line.
Does the air intake ducting all fit with this MAFs?
The original LT1/LT4/L31/L30 MAF's are as you stated approx. 75mm and are aluminum bodied with 3 pins for use with a divorced IAT sensor.
The 99+ 4.8/5.3/6.0/8.1 truck and 01+ LS6 plastic bodied, 5 pin connector for use with integral IAT sensor measures approx. 85mm.

You say that this weirdo plastic bodied, 80mm, 5 pin connector is now being used as a service replacement? I am wondering if you got this 80mm MAFs installed at a dealership, would GM have a PCM flash specifically for this MAFs?
I would think that the MAF frequency calibration table would need adjustment?

I got a brand new 2001+ LS6 MAFs from Global Automotive for $28, shipped to my door up here in Canada for a total cost of $40. Then I went to the GM stealership and bought a 5 pin connector for a 2004 LS6 Vette that came with about 2 foot long pigtails, heatshrink/crimp splice connectors and connector sealant for $55. I wish I knew that GM was offering a 5 pin connector to 3 pin harness. I would have bought that so I don't have to do any splicing when I switch from my 75mm to 85mm MAFs.

I do have to use Boosted Z-71's MAF calibration that he came up with. he made up a spreadsheet that converts the 2001-2002 L31 MAF frequency table into a useable form to use in the non-411 PCM calibrations used in the blackbox PCM's from 1996-2000 GEN 1E L30/31 fullsize trucks.
The GEN 1E L30/31 trucks from 96-2000 have MAF frequency tables that begin at 1488Hz and end at 11216Hz. The 411 PCM that runs the 5.0/5.7 L30/L31 in the 2001-2002 fullsize vans has a MAF table that begins at 1500Hz and ends at 12000Hz.

Boosted Z71 is still using the blackbox PCM because he got a full street/dyno tune done by one of his friends that does calibration work for GM. He spent a day and a 1/2 tuning with his friend. No simple WOT only tuning, they did a proper tune which included the entire load/rpm range. He was concerned that he would have to go through this entire procedure again if he installed the 411 PCM. I wonder if it would be possible to simply copy and paste some of the parameters from a 96-00 blackbox PCM into the 411 PCM loaded with a 2001-2002 L31 van calibration? The parameters and tables are VERY different between the 2 PCM's.

He is running a Vortec 350 with Whipple screwcharger,ETEC200 heads, LT headers, full exhaust etc etc. He dynoed at 430+rwhp using a "white hot" tune. For street reliability they backed off the timing advance a bit and in this state dynoed at 415rwhp. He did an 1/4 mile acceleration simulation pull on the chassis dyno pitted against a modified C4 ZR1 Vette that was also dynoed on this same chassis dyno. His extended cab 4wd pickup beat the Vette in all but the 1st 40 ft of the run and had over a car/truck length over the ZR1 at the end of the 1/4 mile. The Vette ran mid-high 12's.
EDIT: Forgot to mention that he is fueling this beast properly using MPFI in teh form of a crossram marine intake manifold and larger fuel injectors.

peace
Hog

[hquick]

Hey Pauly,
Quite alot of the parameters in the 99+ PCM's are very different to the parameters in the 96,97,98 BB PCM's. They can't be copied across that I'm aware of...although it's been a while since I've looked.
As for the MAF sensor cal...ANY change to the airflow via the intake tube setup requires a re-cal of the MAF sensor. This would also mean a 'different' MAF sensor..especially in this case as it's physically larger.
I had an excell sheet somewhere put together by Lyndon that showed the differing MAF sensor cal's from year to year of the express van cal's...all using the same actual MAF sensor.

[Aloicious]

You say that this weirdo plastic bodied, 80mm, 5 pin connector is now being used as a service replacement? I am wondering if you got this 80mm MAFs installed at a dealership, would GM have a PCM flash specifically for this MAFs?
I would think that the MAF frequency calibration table would need adjustment?

I got a brand new 2001+ LS6 MAFs from Global Automotive for $28, shipped to my door up here in Canada for a total cost of $40. Then I went to the GM stealership and bought a 5 pin connector for a 2004 LS6 Vette that came with about 2 foot long pigtails, heatshrink/crimp splice connectors and connector sealant for $55. I wish I knew that GM was offering a 5 pin connector to 3 pin harness. I would have bought that so I don't have to do any splicing when I switch from my 75mm to 85mm MAFs.

peace
Hog

Hey Pauly, this MAF is actually a little smaller than the MAF like you're running, I had the parts guy get a '01 vette MAF (which I believe is the same as the one your running) and the vett one is a little wider (inner and outer dimentions), this one has the same outer dimentions as the stock aluminum one, but the inner dimentions are larger due to a thinner plastic walls, so the inner measurements are ~80mm (roughly measured with a tape) vs the ~75mm of the stock one measured with the same tape. something also of note was although this MAF has a 5 pin connector on it, its not the same connector as the '01 vette MAF I took a look at, so the adapter wouldn't have worked with your MAF. I'll try to get some pics sometime, but I need to get this fuel pump issue resolved first so it may be a little bit.

I just got this MAF from the parts couter, and the part # matches places like Rockauto, etc and such, so I figured this was the PN GM was using nowadays, I could be wrong. the dealer never installed it or flashed anything, I'm in the process of re-calibrating the MAF table, so far its not too overly different than the '02 L31 xvan stock MAF calibration, but it is a little different. so I don't know if GM would do a reflash or anything.

I'm somewhat familliar with Boosted's setup, but I'm not using a spreadsheet to calibrate the MAF, instead I'm doing a process simmilar to auto VE but for the MAF table to calculate the percentage error for each cell based off wideband data and logging and the such.