Need help from SR20DET Experts (MAFS issue)!!

[uchinan]

Question:
My S14 SR idles great when the MAFS is not plugged in, just like it should (running off the TPS) and it doesnt go past around 2500 RPM. And when I say great, I mean it idles and starts perfect. But when I plug in the MAFS the engine shakes, heavily drops the RPMs (and becomes very erratic as if the timing is off), and seems to be running rich based on the smell of the spark plugs and exhaust. Any ideas about the root cause of this?

Background:
Sorry to be longwinded, but here is the situation to let people know how I got here. I did the typical '95 240sx to S14 SR swap. The 240sx is mostly stock, and the engine, except for the FMIC, blitz SUS intake, and Exhaust, is stock. I did the swap and all the wiring myself, according to the S14 Manual, and I am pretty sure about all the wires since I have checked each one individually for continuity with its respective plug. I have tried 2 MAFS, 2 ECU's, re-wired the MAFS independantly to the ECU outside of the harness, retimed the Engine twice set to TDC, and checked the resistance of every sensor on the vehicle according to the 95 S14 FSM. This problem seems to be unfixable, and I would love it if someone knew what was happening, because this is the toughest SR problem I have ever encountered. Thanks

Wires Connected on the F4 - M63 couple:
-TACH
-Water Temp
-Speed Sensor
-Neutral Sensor
-Fuel Pump
-MIL
-IG Power
-STSW
-IACV-AAC
-(+B) Power
-Injectors and IGN Coil Relay are both connected to the IGNSW power source (main black and Red wire)
- Wiper stuff (which is almost entirely the same on the harness)

[silviasichigo]

It is not uncommon for two MAFS to be bad I also have a 95 Silvia. Before I changed the S-14 MAF to the Z32 MAF I was haveing the same problem real bad shuddering and shaking, Well I took the MAF apart and cleaned it with a Q-tip and some electric parts cleaner and as soon as I hooked it up and started the car it ran smoothly. But that is just one of the many things that can go wrong with the MAF if you buy a Power FC D-jetro then you can go to a MAP sensor and it will solve all of your problems with the MAF since you will no longer need it.

[Id-]

is the maf getting a ~constant voltage when idling (or at least attempting too)? got an AFC? it will tell you

[speeddreamz]

like u said, no maf, car runs good. and when plugged it runs shitty, bad maf. It also hesitates(and bogs) during daily driving rite?

[wootwoot]

a good way to clean it is to take the maf off, put it in a plastic bag with isophyl rubbing alcohol and shake lightly. double check that, i think its right. if that doesnt work then time for a new one.

[uchinan]

Yup the MAFS is getting a constant 13.5 volts when the IG is on. Also I tested the voltage coming out of the (S13) MAFS when the car was idling (poorly) and it read as it should, around .9 - 1.0 volts at idle, and around 2 volts at 2800 - 3000 RPM.

I would agree with the bad MAF theory except one thing. Both of the MAFS I used came off cars that were running perfectly. And I tested them for voltage. One was an '89 US 240sx, and the other was a '93 Silvia S13 SR20DET. I was told by people who have done an S14 swap before that the S13 and S14 MAFS are the same, but this is my first S14 so I don't have the necessary experience to know (and if that is the problem I will be pissed)....Anyway thanks for the ideas so far, I may go try and clean the S13 MAFS.