I have only one problem with you'r situation.
Try taking the MAF completley off and run the engine, it still runs only the CEL is triggered.

Or keep it connected to the harness, but simply put it aside and remove the intake tube (leaving the TB open). It will still run.

That's why i don't think you have problem with ari/fuel ratio.

Than again you put the stock MAF electronics in to a bigger housing, right? So why wouldn't it work.
It dosn't realy matter how big the oppening around the sensing element is, because it's in the center it's not rading the "amount" of air going through it, it reads the speed of the air.

Try measuring the output using a tester and blowing on the element, the stronger you blow the higher the output (or less or more, can't remember, the resistance will be).

BCBMDE, as I said before, I did not switch out my actual sensor, only the housing. [color:"red"] [/color] There is nothing wrong with the MAF sensor. I state again. [color:"black"] [/color] The only thing changed is the housing. If anyone were to actually look at the stock MAF in your Isuzu and take off the screen, you would see what I am talking about how restrictive it is. Even taking into consideration using a non-altered throttle body, the MAF is the biggest constriction in the entire intake. Short of putting an air-flow meter in the intake to measure cfm, it's definately pulling more air. I assumed, and we all know what happens there, that the ECM would be able to adjust automatically. Apparently not. I will be able to tell for sure when I get my gauge hooked up tonight when I get home. And for the record, when I purchased my MAF ends (used), I also got free a MAF that was for that size intake. I tried it as well, and got the exact same results. The only difference that one can even tell is that there is a little extra plastic on 2 small tabs due to the smaller opening that protrudes into the MAF body. Instead of trying to pick holes in an installation, which I am fairly meticulous about, please someone give me some concrete knowledge to go against a lean air/fuel ratio. I think Randii was on the money about the fuel map being offset due to a lower flow rate. Everything I've read about using NOS, Supercharger, and Turbos point to having to adjust EFI's to take into account the extra volume of air.

Ok...I'm on the same page now. Sorry.

You have the same volume of air passing through the entire intake as you did prior to the new housing (you haven't added forced air induction). The velocity of the air through the intake has decreased though. It has decreased proportionally to the cross sectional area increase, and the ECU thinks you have almost no air coming in.

Q = Flow rate of air
Vstock = Velocity of air seen by MAF
Vmod = Velocity of air seen by MAF
Astock = Cross sectional area stock @ sensor
Amod = Cross sectional area after mod @ sensor

Q=V*A
1) Q = Vstock * Astock = Qmod * Amod
2) Vmod = Q/Amod
1->2) Vmod = Vstock * Astock / Amod

Area of a circle = PI * R^2
If R is increased by 2, the Astock/Amod ratio = 4!!! Meaning that the velocity of air the MAF reads in one quarter that of what the ECU expects (this is a made up ratio, but you get the picture).

O2 sensors are designed to pick up a lean condition, but they must be warmed up to work (and the ECU knows this). Perhaps a simple reset of the ECU via battery disconnect is what is required, but I doubt it.

Perhaps we can trick the ECU into thinking that there is more air velocity coming through than it is measuring. Measure the resistance of the MAF @ idle under two conditions, stock and with the new housing. Then add some resistors in series (or in parallel depending on what you need to do) to correct for the idle problem (probably won't help when you're into the throttle though).

I think you're expecting way too much out of the ECU and will have a very difficult time getting it. Best of luck and let us know how the fuel management device works out.

I respect the creativity, but I worry about your engine survivingthis trial and error. That said, everybody probably thought Ben Franklin was nuts when he started flying a kite in the rain... mebbe you'll get a strike of lightning (of course, there's good and bat to that!).

From what I understand of the fuel map, it is a multidimensional curve (oversimplifying more than a bit to fit my basic understanding), and changing airflow just offsets that 'curve' in one dimension, leaving the rest unchanged. If you do this within the 15-25% window of change that the EFI computer can adapt to, your results may be positive. The challenge, then is after you've knocked the map off one way, nudging it back into the window with other adjustments (fuel pressure, injector flow, and so on). The problem is that few folks can truly do this. More power to ya for trying, but be careful, man... running too lean can cause an engine to try to burn more than gas, like pistons. <img src="/forums/images/graemlins/shocked.gif" alt="" />

Hopefully Turbo Dan will see this and comment -- he's designed several turbo setups and a supercharger setup, and has been running his 4ZE1 well outside of sane boost for some time, yet it continues to survive. He's also running a fuel injection setup of his own devising, and has forgotten far more about fuel injection than I think I will ever get to know...

Good luck with this, Xanatos, and I look forward to your results -- but instrument the hell out of this so that you can stay well this side of expensive failures...

Randii

Xanatos
Don't forget to look at the most obvious things.
Always make sure when you do anything different to the maf air flow you make sure you disconnect the neg cable for 15 minutes after installing anything that is going to change air flow to the maf.
You need to reset the codes to the air and fuel ratios so the computer knows that there has been a change in flow and adjust accordingly. And this is done by disconnecting the neg cable.

Good Luck!! <img src="/forums/images/graemlins/cheers.gif" alt="" />

Ruben

Hmm, until I see an actual pic of YOUR MAF and how you made those ends for a 5.7L chevy motor work I'll hold off on giving a final opinion on this, but heres the vibe I'm getting.

You're using a MAF thats designed to be in a certain diameter housing that will allow a certain ammount of air through it. Now you have replaced the housing with a larger one that allows more air in without recalibrating the sensor. IMHO the sensor is probably still sensing the original air volume and giving those readings to the ECU, but the new housing is allowing much more air in. Essentially you have a big ass air leak in your intake that the computer cant account for. Thus your lean condition.

Dallas

I don't think anyone is picking apart your installation. I just think there is something that is messed up that you have not identified yet. I don't think you could get so lean as to not idle. Lean is going to show up under load. You are heading down an expensive path that might not be necessary.

That said, your description sounds like a post-MAF air leak. I think Dallas is on the correct path. The sensor is setup to read the incoming air based upon the cross-section of the stock MAF. Same sensor in a bigger hole is going to give you a reading that under estimates the actual amount of air flow. Also, how is the sensor sealed in the larger MAF? Any other places for leaks between the MAF and the TB?

Good Luck,
Michael

Well I'll throw something else out there - is there a vacuum leak, maybe a hose that came off during your install process?

It reads like you built a venturi tube. If you widened the area before the MAF intake and after, the velocity of air (not just volume) moving through the MAF is going to increase. I'm thinking the MAF (being a dumb piece of electronics built for "stock" conditions) is thinking the throttle is opened wider than it actually is, so it's sending a signal to the ECM that runs counter to what the TPS is signaling. I've never seen an order of operations on these electronic ignitions so I don't know which signal takes priority, but it would be logical to think that the ECM might over correct in some way or lacking clear signals is stuck trying to figure out what's happening.

Ok, here's an update fellas. Put in an el cheapo gauge to get at least an idea where I stand. I started first without the mod to see a baseline. I'm getting a slight rich read at WOT, but I'm running really lean on my idle. When I reset my computer and put the altered MAF in, to my suprise, I wasn't lean, I was way rich. My sputtering is apparently coming from the engine trying to flood itself. Go figure. Anyway, I'll update everyone once I get my a/f regulator installed and play with my a/f ratio at various rpm points. The unit I have will let me adjust 11 points in 50 rpm increments from 500-8000rpm. Of course I won't need to go that high seeing as how we redline around 6500 right?

Here's a quick question though. Anyone know if a new wide-band planar type oxygen sensor can be put in place of an older narrow-band one? Or should I just install it separately when I get a wide-band a/f ratio gauge and use it only for that. Also, which Oxy-Sens should I be getting my signal from on a narrow-band gauge? I was going through my shop manual and see a diagram for four sensors A-D. Only two of them, from what I can read from my electrical diagram, feed a signal wire back to the PCM. Any thoughts?