Problems Running/Idling

[amreboot]

I just dropped in my freshly rebuilt VG30ET 7.8:1 CR

Following mods:
t3/t04e 57 trim
440cc bosche/ford injectors (low)
88t ecu w/ nistune (the 3 resistors removed for fitment of z32maf)
z32maf (N62)
walbro 255lph fuel pump

So it cranks, it starts, it kinda runs...
It sounds like its missing on 1 or 2 cylinders, I will have to check

On the stock z31 maf map, it will kind of hold an idle, but when I switch to the z32 maf, it starts and runs a little better but doesn't hold an idle at all.

I haven't altered any of the wiring for the z32 maf and I was reading that maybe one needs to...

Anyways...
Suggestions on my problem?

PS - timing belt is dead on along with the distributor being set properly.

[Matt]

yeah it would be the rewiring for the Z32 MAF you didnt do... Its kinda important!

You need to modify the ECU to accept a 0 - 5 volt output from the Z32 MAF where previously the Z31 MAF was about 2 - 7 volts

Then you need to make sure the MAF calibration wire is about 370 ohms connected to ground because the Z32 MAF doesnt have this

It will stop everything working with incorrectly interpreted load signals coming into the ECU

[amreboot]

Looking at my harness for the MAF, I don't have a wire on the end that goes to A, its just blank.

Maybe they did away with that in 89.

Any other ideas of why its not running well?

[DuoWing]

Hmm you know this is really odd and I'm glad someone else came across this. On my L28ET when I converted the 83' ECU/AFM to the 86' Z31 ECU/MAF I noticed that when wiring the MAF up it was missing a pin/wire on the A slot. I didn't know why, but what I ended up doing was cutting up the plug for the old L28ET AFM to pull the pin out of it and add that to my Z31 MAF plug. Just an idea if you can find a spare plug or any pin that will fit.

[amreboot]

Is this something that needs to be done?
So should I go out to a junker and get the pigtail from another z31 and do the mod?

[Matt]

this is from the software users manual - page 36

Z31 VG30 (2 - 7 volt)
Pin A = Calibration pos (variable resistor)
Pin B = output voltage (black shielded 2-7 volts)
Pin C = ground (black - chassis)
Pin D = ground (black - ECCS)
Pin E = battery source (12V black striped)
Pin F = self cleaning mechanism (not used with Z32 MAF)

* Sensor and Chasis grounds are the same and are connected together
* Calibration pot must either use a 500 ohm variable resistor set to 382 ohms or 1/4 watt resistor 370 ohm

with that wire hanging off at the moment which used to go to A... visit an electronics shop and get a 370 ohm resistor (or near enough) and then wire that from that wire to the black ground wires

that calibration wire is simlar to K constant and will adjust your base AFRs, stock value appears to be 370 ohm on RB30 AFMs

[amreboot]

I already have a 370 ohm resistor ready to go in but my maf pigtail has no A pin on it.
What should I do?
I will post a pic later on tonight.

[Matt]

pig tail? are you talking the MAF connector?

just get the wire coming out of the MAF loom and wire that to the resistor

if you cant find it in the MAF loom then see if you can locate it on the ECU plug side

[turbobluestreak]

I thought 88-89 Z31 US Market ECUS didn't use Air Meter Pin A? On 88-89 pin 30 goes to EGT for Cali models. In 84-87 pin 30 goes to Air Meter Pin A. If I'm wrong let me know so I can add the resistor to my wiring for my 88 ECU.


tbs

[amreboot]

There are no pins in A from 88-89.

[Matt]

I've seen that most of the later Z31s drop this wire also. I would assume the ECU has some default value when this is not connected