MAF Replacement Questions

[Jesda]

Well, it turns out my occasional fluctuating idle is related to the MAF connector. At least I'm pretty certain.Of course, my alternator is still bad because I have barely enough power to hear the door ding or power the interior lights if I leave the car parked overnight without the battery charger.

Previously, I cleaned the MAF and wire connecting point. But today, out of curiosity, I wiggled the entire wire piece that goes to the connector, and the idle started to decrease and increase.

Question is, can I just buy a new wire/connector? I think the MAF itself is okay -- I can tap on it and its fine.

Also, I went to check the ECU codes but I guess that's silly, since the check engine light didnt come on. I did find out that I have a Nissan remanufactured ECU.

Sometimes, lately, I wish I had a bicycle.

-Jesda

[elwesso]

You can get a new MAF connector, but how did you clean it... Youd have to splice, reconnect the wires..... I wouldnt recommend unless its necessary.....

[Jesda]

I sprayed the contacts and went at it with a q-tip. I didnt do any splicing and connecting.

Will I need to purchase the entire wire or just the end piece that I can cut and reconnect?

[elwesso]

Alright.....

Did you clean the contacts on the HARNESS connector, not pins on the MAF...

You can get the harnes (I can get you one Free) and youll cut, and splice the new one in.....

[Jesda]

You rock!When I visit, we need to take a ride in the Gremlin blasting Bohemian Rhapsody.

[Q451990]

I've had some luck tightening the contacts on he harness side with a dental pick. Dielectric grease is a good thing to have on hand too.

The remanufactured ECU was probably installed as part of a transmission replacement. They did this on mine back in 1997 - new ECU and TCU. Something about changing the shift points, etc. I wish they had given me the option of a 93 TCU instead

Heath

[PoorManQ45]

kind of on the same subject.

If you had to replace the MAF sensor, isn't there one from another vehicle that works with the Q? I thought I read about that somewhere on here.

For another MAF to work with the Q, the voltage output range would need to be the same on the low side and maybe a little higher on the high voltage side, right?

I had to have the MAF replaced 4 years ago. I didn't work on the Q myself then. It cost $400 for the Nissan dealer to do it.

[Rex]

I've heard of some 240 guys using the Q's MAF for their motor swaps, but not of another cars MAF being used in a Q. DO you recall where you saw this info?

[1992Q45A]

I believe it's the same MAF from the r32 gtr. I fyou look on ebay they mention it with the Q45

[elwesso]

I've had some luck tightening the contacts on he harness side with a dental pick. Dielectric grease is a good thing to have on hand too.

The remanufactured ECU was probably installed as part of a transmission replacement. They did this on mine back in 1997 - new ECU and TCU. Something about changing the shift points, etc. I wish they had given me the option of a 93 TCU instead

Heath

I mirror that.. you want to try and make the stock harness as good as possible becuase splicing can lead to not as accurate readings.....

Fix what you got, then replace!

[IvoryJ30t]

the GTR's use two maf sensors [60mm each]. the q45 is the only nissan that i know of that uses a 90mm maf.

[Q45tech]

No substitute as the ouput voltage is critical to 0.001 volts for proper injection level [open time].

[PoorManQ45]

What is the other type of air flow sensor? It measures the air density or someting like that. IIRC, it is less restrictive than a standard MAF. Do you have any info on this Q45Tech?

[IvoryJ30t]

karman-vortex

the hotwire maf is less restrictive.

[HeavyDuty]

I think he's referencing Speed Density engine management, like the early (86-88 49 state) Mustang 5.0's, Honda/Acuras, etc.

Why not just fab up an intake & install a 650 double pumper with mech secondaries?

[IvoryJ30t]

oh, ok.

with speed density, there is no airflow sensor.

the computer uses a MAP sensor [manifold absolute pressure], a temperature sensor, and the known parameters of the engine [rpm, VE,] to calculate the airflow.

i prefer MAF systems.

[HeavyDuty]

[Q45tech]

The MAF has a whopping 6" water column restriction that's 0.21 of a psi or 1/5th of 6.8% or 1.4% at 7,000 rpm ............about 1.1% at 6000 rpm maybe 2-3 HP at the worst............at 4,000 rpm the restriction is much smaller about 0.25% or less than 1 lb/ft of torque.

The MAF is 2- 3% accurate whereas the MAP may be 5% or worst . Usually having a MAF creates more HP/torque than the old fashioned MAP.

The Harman Vortex version of a MAF is very accurate at low flows but less accurate at high flows vs the Bosch patent hot wire method which is very accurate at high flows.

The MAF can follow changes with engine wear [or problems] whereas the MAP cannot!

[IvoryJ30t]

exactly, if the intake gets carboned and the flow decreases, a map system cannot account for the changes, and will run rich.

just like if you add intake and exhaust to a map system and dont retune. the ecu does not know that you changed the motors VE, and will lean out. thats how alot of rotaries die.

[Q45tech]

We had a bad MAF which only read about 0.2 volts high 4.6 vs 4.4 volts yet the injector time was 20% too rich [12 millisecs vs 10 millisecs] at 6500 rpm.

Important to understand how critical the EXACT correct MAF voltage is.

Once you get out of closed loop [acceleration] the MAF has no correction by O2 so it supplies a right or wrong voltage to ecu which responds with fuel.

Never really tested how much [injector open time] the MAF can force at the above 4.4 volt range...........obviously 20% extra fuel could burn 20% extra air to create 20% more power 280> 336-340 HP ----all one needs is the air pressure.