Hey everyone. Alittle background... Car is an 87 TA, drivetrain is from a modded 99 z28. Previous owner has an SLP 85mm MAF sensor installed, and the car is tuned...should be fairly decent tune as well.

I have been getting a code P0103...which is a high frequency code for the MAF. I also have an Aeroforce Interceptor gauge installed, and when I select MAF frequency...it stays at zero... No fluctuation at all. The car feels good. Drives good, has good power...but I feel like there should be more in it.

My questions are as follows. Whats the easiest way to go about testing to see if the MAF is actually faulty.

If I buy an 04 Z06 85mm MAF, and install it, will that screw with the tune too bad??? I have a line on one of those locally that I can snag.

I plan to take the car to get tuned pretty soon. After I swap shifters and fix a few loose ends. Im just worried that if I install the Z06 MAF that it will really scerw with the PCM. Ive heard so many bad things about the SLP unit...and I know that it already messes with the PCM...

I did some searching, and didnt really come up with too much. Any ideas on this?? I assume that since the MAF is reading 0Hz, the car is running in SD? That woudl cause some power loss since the car isnt tuned for SD correct? might even possibly run rich?

Thanks in advance! Let me know if I need to provide more info...

Justin

 

Whether it runs rich or lean in SD will depend on the VE table values. If the MAF shows 0HZ I would swap it with another MAF and if it works then tune the MAF table for the new MAF.

 

Yeah I figured it would need to be tuned. But if I use the 04 Z06 MAF without a tune, will it run badly? Or hurt the engine in any way? because it will be awhile before I can go get a tune. I need to start talking to Mike at Rapid so I can set something up and figure out exactly what I need to do.

Justin

 

It depends on how modded the engine first of all. It shouldnt hurt it without a tune, but the LTFT's will probably go up or down and WOT will probably be off target a bit. Car still should be ok for normal diving until you get a good tune.
remember that the PCm has a certain degree of self learning ti can do to make up for variances.

 

Hmmm...ok. Well the engine is fairly modded.... Ill post the list. Maybe Ill snag that Z06 MAF, and try it out. The scan gauge I got can show fuel trims both short term and long term, as well as a few other functions...so maybe I can sort of monitor things so nothing goes too wrong. Im starting to wish I had a laptop and HP Tuners now... I almost got it...but couldnt afford a laptop at the time.

Here is the list....

Description of the motor:

Shortblock is an ARE shortblock:
Polished Stock Crank
Resized Stock connecting Rods
Ross custom boost pistons (with valve relief's)
Childs and Albert Plasma Moly Rings
Clevite race bearings
ARP rod bolts
Rotating Assembly Fully balanced
Engine Blueprinted.
ARE ported oil pump
MTI 2e 5.3l ported heads, milled .030 with double springs and new pushrods
228/224 113 +1 Comp XE-R cam (currently installed with another 2* advance)
Cloyes adjustable timing chain
LS6 Valley Cover and PCV system
FAST 90mm Intake and TB (and bellow)
SVO 30lb injectors
SLP 85mm MAF <------Thinking this is my issue....
ASP underdrive crank pulley
Hypertech 160* T-stat
LT Headers w/ 1-3/4” Primaries


Justin

 

Bump...

Can I assume that since the scan gauge says 0 for the Hz of the MAF, that the MAF is in fact junk? Assuming all the wires and connections are good of course...

I just dont know what else to check out. I think the car is running "off"...but not horrible. I still think it could run better...and have more power. I just dont want to hurt anything.

I was advised to ditch the SLP maf for a z06 unit...however I dont know what that will do for me before a tune. And I dont know when Ill be able to get a tune. I dont want to slap the z06 maf on there, and have the car run worse than when it has the SLP crap on it...

Along with the z06 MAF I need to grab a nick williams throttle body. That FAST thing is giving me fits too I think...

Justin

 

I had the same thing happen with my 85mm maf and it was the adapter harness. The one wire had a bad joint.

 

OK... I planned on taking it off during my lunch break and testing it out...see if thats doing anything goofy.

If it is...and I fix it, will the computer just start reading the MAF again on its own or is there something I have to do to FULLY reset the computer? I can clean the DTCs with my scan gauge...Will that do it?

Im really hoping a wire took a dump...that would be sweet! Still ditching that SLP maf before I go for my tune though. Just too many bad stories about it.

Justin

 

Scratch that...I just checked the adapter and it seemed ok. I havent checked the out puts from the engine harness yet... I assume one is ground, easy enough, one is power...not sure on the voltage but I could find it probably...and the other is a signal wire. I would have no idea how to check that. My altenator wire was broken near the plug...so I see no reason a wire couldnt be at fault here. I might just have to face the fact that the MAF is junk too...

Im correct in saying that the MAF freq should NOT be 0 at idle right? There should be some sort of reading. and That reading will go UP with engine load??

Justin

 

Your correct in saying that. At idle its about 2000hz to 3000hz from memory, certainly greater than 0hz. and yes it will increase with engine load, about 8000hz at WOT or perhaps even 10,000hz, depending on how much air you car is using.

 

Is there a test procedure for testing MAF functions at the harness...similar to testing a TPS sensor? Like using jumper leads and testing for voltages etc... I tried searching but didnt really see much... I havent looked in the haynes book yet...but the info in there is pretty sketchy in general.

Justin

 

An ociliscope would be the ideal bit of kit to look at the waveform. They can be expensive. I picked up a portable one for about $150.

The signal is in the form of a sinewave it cant be seen on a volt meter, as its not a DC voltage.

Perhaps visually check the MAF where the air passes over arnt broken, there are a few resistors between the wires. Thee are very fine wires and cleaning the MAf can easily break there.

The MAF has 0V and 5V (or 12V, not sure) going into it and the other wires is the signal. Check you have 0V and 5V on the connector. If you do, it could be a dodgy MAF. To check if you have 0V on the MAF connect you positive prove of the meter to 12V battery, and the neg side of your voltmeter to the pin you think is 0V, if you see 12V, then you know you have a good ground. (what ever you do make sure you have the meter on Volts)

 

Ok...Im going to try to test as much as I can with a multimeter to confirm that atleast the wires are in good shape.

I picked up a reman. 04 Z06 85mm MAF today at autozone... yeah... In stock for $70... I think I might just plug it in and give it a try. See if I get a reading on the MAF Hz atleast.

I think something is really goofed because if I take off hard, I can spin in 1st, but when I shift hard into 2nd I dont even get a chirp. The car rockets... I feel as though I should be able to ATLEAST chirp them in 2nd...even if I dont speed shift the car.

If I hook up the z06 MAF, and get a Hz reading... What are some things I can look at to make sure nothing is going relaly wrong with the engine/tune. I can view long and short term fuel trims, and o2 voltages, and injector pulse widths...maybe a few other things with the scan gauge.

Justin

 

Ok...stupid issue. I wasnt getting 12v power to the MAF sensor. Not sure why. Probably something I overlooked when I built my harness. Well...when I modified my harness. I was also throwing codes for both o2 sensor heater circuits. What do you know...no voltage going out to them either. So I got 12v running to that circuit, and plugged the SLP unit back in, and the scan gauge shows around 3k Hz at idle. Not sure what it goes up to at WOT because the roads are wet. So it seems as though the MAF is atleast funcitoning again.

I wont know til the weather clears up if I gained any power or not. Even then I still might not know. Also tomorrow after the drive to work Ill check for codes and see if the o2 sensor codes went away. I guess there is no hurry for the Z06 MAF now. Ill take the one I got from autozone back..that'll make them happy. haha. Nice big return.

Is there anything I should do to "reset" the computer now that the MAF is functioning? I mean...if its sending the signal to the PCM then the car shouldnt be running in SD mode...and it should just pick up with the regular MAF tuning...correct? I cleared any DTCs before running it...but I wasnt sure if I had to disconnect the battery for a period of time or do anything else to it.

THanks for the input everyone! Thats one more little issue checked off on the short list!!!!

Justin