Here is some good infomation I have come across for you all. This was discovered by them while testing thier intake for the 5th generation Camaros and hence the same issue has been reported on several Corvettes with either the LS3, LS7 or LS9, mainly after the install of a intake because of the increased airflow. There have been reports from serveral people of hesitations without a intake install and this has been known to fix those cars as well. I have these available if you check and find you have a "weak" one. They are all double verified once when new stock is recieved then again once it is shiped.

This was from Vararams web site.

The Air Meter


During our testing we discovered a disparity between identical Camaros in terms of there reaction to changes in airflow and weather conditions.

We noticed that one car would be finicky at cold start and the MAF would scale "weak" while others would be strong and clean.

What we discovered was that the 'WEAK" meters were reading 1560-1670HZ at idle with the A/C off (OEM is 1800MHZ+)
During on road, light throttle input the MHZ would be slow and weak to respond to throttle changes (hesitation)
Wide open throttle showed 120-170MHZ lower than OEM stock (OEM is about 8600MHZ) on the same car.

Weak Meter Fuel trims-
The fuel trims would go to -15% using a VR -3% for a panel filter and -5-8% for other intakes. MHZ would drop as would the idle. When the MAF scaled in at WOT each would richen up accordingly.

Test 2 we pulled the filter from the VR completely, this resulted in fuel trims dropping down from -15% to -24%, MHZ dropped another 70-90MHZ. The car would drive fine but WOT operation was basically weak/flat and timing was low etc...
Now with one simple meter swap which takes about 1min the car immediately corrected, went back to 0% fuel trim MHZ jumped back to 1800+ all within 30 seconds! The car drove like a Rocket!

We began final confirmation by swapping air meters in cars and doing volt meter testing in static conditions. 30 meters, 3 cars = the same exact result every time. We confirmed this with VR customers tuners around the US.

The Result is that these 'weak" meters are not showing the same resistance levels as the majority of OEM meters.

This lead us to contact the GM rep and the actual manufacturer of the meters (its not Dephi) They confirmed the factory which allow us to identify each meter.

These numbers and letters are located on the back of the meter as shown.

(WHAT TO LOOK FOR) The factory code.




The suspect meters have all consistantly had a single letter located in this area VS a number with a letter.

Here is the catch 22

If the airflow is not changed by a substantial amount (our flow testing verifies that most of the aftermarket boxes do not) over OEM then the meter will be within OEM Tolerance but will always be "weak"
you cannot tune this out, its a fundamental issue with the resistance of the meter. It needs to be replaced. This is why some cars are finiky and some are not.

 

Excellent information!

Thanks for posting it.

 

Patrick, are these findings concrete and verified? Is it for certain that all meters just with one letter are indeed bad and the ones with a letter and number are all good?

 

Patrick are you sure you got the right information. From what you are stating above that the MAF is reporting a lower than normal reading. The fuel trims should be showing a positive correction rather than a negative correction. If its under reporting the correct air flow the o2 sensors should be reporting a lean condition and the fuel trims should go positive to correct the lean condition, and if it goes high enough then the PCM will set a DTC(s) to report a lean bank 1 and or 2.

I have worked on several gen 5 F bodies with all sorts of different mods and I have installed CAI of brands other than the VR. I have never ran across a "weak" LS7 style MAF in any F, Y or GM truck lines. At least not yet. Did this problem exist with the stock air box? Many times with the VR in a Y body, because of its larger cross section MAF tube, the air flow velocity slows down and the result is that the MAF will under report the actual air flow, a similar condition existed in the early Halltech Killer Bees and now with their race style super bee in the larger sizes, Jim has corrected this with their "no tune required" killer bee. But for those that want the large CF112 race version tuning is required and there is no way out of it.

 

The situation mainly only arrises when an aftermarket intake is used. If the stock system is maintained then there is often not an issue. So it is really not bad most of thje time if used with a stock air cleaner, just when a higher flow one is installed then is when it start having problems

 

But like tjwong states the fuel trims will show positive not negative if this is the case. Care to comment?

 

I didnt do the testing myself and am not an engineer as to how GM's computer will read and interpert the information. I am just passing on information you may find usefull

 

I just checked the MAF on my '07 Z06 and, sure enough, it has a single "M" as the factory code. I've tuned the car myself and noticed that the MAF airflow frequency vs. airflow numbers seemed low compared to other tunes.

Is there any issue with these "weak" MAF sensors other than the lower readings? I'll probably need to order a replacement and see what happens.

 

That's cool Patrick. Not discrediting the info just trying to understand more why no other tuner or air intake manufacturer has come forward with this info. I know mine was logged by my tuner both at idle, on the road and on the dyno and it reported properly but I have not checked mine to see what designation letter or number combo mine has. I must admit that I am curious now though.

 

This is just a similarity they have found amoung cars that had an issue. So if you are not having a problem dint worry about it but if you are this is something to try

 

A M would be a weak one so to get more accurate readings you may want to replace

 

That basically means that the MAF sensor itself is not the issue. The root cause is because one, the GM MAF sensor is a calibrated device made to work with the stock air box. If one deviates from the design then of course the sensor won't be telling the PCM the correct information. This is because higher flowing intakes that differ from a stock unit will have a larger cross section area or in otherwords a much larger ID in tube size, a larger bore means that the velocity or speed of the air flowing across the sensor will slow down thus the lower reported signal to the PCM. So the engine actually sees the same amount of air but the sensor reports a lower flow rate, then the primary o2 sensor says "WTF we are lean give me more fuel" the PCM complies and raises the long term fuel trims to compensate. In a nut shell that is whats going on. Just my two bits.....

 

makes sense to me thanks for the insite

 

Interesting. I am getting some hesitation at light throttle and low RPMs that I attributed to the cam. Pulled the MAF this morning, and it's "D". I'll swap it to see if it corrects that hesitation.

 

Thanks for the info. More or less confirms what I've been seeing with my Airaid, not to mention it sounds like crap at idle do to running lean.

 

let us all know how you made out

 

your quite welcome

 

I will report back after it is installed. The one I just picked up is a "K12".

 

There is a difference, and this "weak/strong" MAF issue has been found on the camaros first, I think.

The issue is just that some are a bitch to tune, and the target is always moving, while others clean up in a few cals, and run great.

 

So can anyone confirm, if there is indeed a difference, if the ones with a single digit letter are ALL troubled mass air flow sensors, and ALL of the ones with a letter and number are NON-problematic?