question about maf sensors

SouthArk370Z

Standard safety procedures will mean the car is in P or N, ie, no load.

__________________
Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub
Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

phunk

I havent seen that stated anywhere.

But I think I will step aside and let you spearhead the diagnostics of his MAFs

__________________

SouthArk370Z

If the Nissan engineers wanted the engine tested under load, they would have said so. Procedure says to hook the harnesses back up, start the engine, check idle V, rev to 4K, check V - no mention of loading the engine.

Please don't. Everything else in your post made very good sense. Going by the many "odd" problems OP is having with his Z, it looks like he needs all the help he can get.

__________________
Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub
Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

Z_ealot

If it helps any my scantool reads the airflow at idle at 3.5 g/s

SouthArk370Z

Since, as phunk said, it is unlikely that both MAFs went out at the same time, I'm still leaning toward a high resistance somewhere in the wiring common to both MAFs.

You said you had 12 and 5 V at the MAF harness connectors but that was at no (electrical) load. To check for high resistance between source and sensor, you need to check V when the MAF is operating.

But it's possible that they went bad together. With all the other problems you are having, it wouldn't surprise me if they all have a common cause, ie, wreck, water damage, etc. I'd see if I could find someone that would loan me (or sell cheap) a known good, used MAF and see what it reads before buying a set. If the same MAF is used in other, more popular Nissans, it will help your search. CourtesyParts.com has a good parts look up for 370Z - look and see if they have some kind of cross-reference for part numbers.


Edit: Or you could have a problem totally unrelated to the MAFs. Lots of weird things going on with your car.

__________________
Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub
Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

Z_ealot

Did exactly that while i was waiting for a response....both connectors show 12V or above while engine is operating and same for the 5V reference wire

Edit: went and double checked since i could not remember exactly....both bank 1 and bank 2 12V wire reads 14.1 volts while engine is running while bank 1 5V reference wire reads 2.54V and bank 2 5V reference reads 1.30V while engine is running and harnesses are connected to mafs

SouthArk370Z

Maybe you do have two bad MAFs.

Have you cleaned the MAFs and changed air filters?

__________________
Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub
Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

Z_ealot

Cleaned the mafs multiple times and air filters are brand new changed out 3 months ago and no leaks or blockages in intake tract or intake manifold

Jhill

Late and tired so didn't fully read everything but honestly I would never ever ever diag MAF's with a basic DMM. You really need a scope to watch the curve. Even with that it has to be fairly fast for some cars today, my old scope I had I car I absolutely knew it was the maf, I could just tell by the sudden fuel cut and then jump right at 2k rpm it had to have a drop out but my slow scope couldn't see it and now sadly that scope screen is deing so a PICO may be in my future but a DMM for maf, nah.

Keep in mind your scan tool baud rate is not as fast as your PCM inputs just an FYI.

Z_ealot

just an update, but I decided to disregard the maf sensors for now and look at the main issue which is the fuel trims indicating a lean condition. decided to start with the simplest thing I could think of which is the vacuum hoses and pcv hoses and valves. brake booster hose and all other hoses connected to the intake manifold or had anything to do with vacuum checked out visually OK so moved on to spraying around each hose to see if that did anything....nothing. lastly decided to pull off the hoses for the pcv valves and guess what I found.....a nice little puddle of oil on the connectors where the pcv hoses meet with the intake manifold. pulled the hose off the pcv valve itself and same thing so popped one of the pcv valves off for testing and here's the video of what I found.....



if I remember right from reading around these valves shouldn't be hissing like that and there should be next to no suction at idle if the valve is operating correctly, can anybody confirm this or am I getting faulty information?

P.S.

when holding the valve in my hand I can feel vibrations coming from it while vacuum is being applied to it.

phunk

totally normal.

__________________

Dreadnaught

It sounds like there is a hole in the PCV hose where it meets the intake. This could definitely be why you have been running lean since there is unmetered air entering the engine.

__________________
Ford Diesel and Heavy Line Technician at your service.

Z_ealot

So this information is wrong?

AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - What are the Symptoms of a Bad PCV Valve

Also, the system has thrown a p0171 at me before in case that helps any. I replaced both the throttle body gaskets and the upper intake manifold gasket thinking those might be the culprit and havent had that code come back after that but fuel trims still indicate a lean condition.

phunk

Only if it says the video you posted isn't normal!

__________________

Z_ealot

Shouldnt there be no oil in the pcv hose though if the valve is functioning correctly?