mmjb

If anyone can help, im in a bind. I looking for the ecu ground wire. I know where to ground it but i don't know where the wire is, color, etc... This is for a 1988 s4 TII rx7. I'v looked at fsm but it dosen't say where wire is located or what color it is.

NZConvertible

The ECU itself has three ground wires, which join together with many of the other ground wires for the rest of the EFI components and bolts to the top of the engine under the UIM. All these wires are black. Look in the FSM wiring diagrams for more info.

What are you trying to do?

mmjb

im trying to find the ground wire, because i did a rebuild, and now i can't find the ground wire that goes to the rear of the engine. I looked at the FSM and found the location of where the wire bolts onto the engine, but i can't find where its coming from. Basically i have no ecu ground and im getting horrible hesitation at 3.8-4k rpm, and horrible low rpm hesitation also.

NZConvertible

If the engine's running, then you do have an ECU ground. If it wasn't connected then the engine wouldn't even start. It should be bolted to the top of the rear rotor housing.

mmjb

ok, well ill start looking for any other ground i might have missed, thx for your input.

gotrotors?

your major ground is under the uim, its a black wire (a pair actualy) on a round washer style connector. the ground from the rear of the engine (tranny actually i think ) goes to firewall.

rotary_yankee

well i'm trying to figure out which wire is the ecu ground. I'm trying to reground the ecu because after grounding the chassis, the ground under the UIM,which improve the ride a little , i still have the hesitation. so i figure if i ground the ecu which would help the ground for the boost sensor and the afm. my problem should be solve. I hope.

so if you could tell me which wire or color of wire please do so.

gxl turbo 2 1988
fcd
greddy fmic
remove all emission
3 inch dp and RB exhaust system aslo 3inch
custom intake
rebuilt motor about 150 miles on it
walbro fuel pump 255
2 sparco seat red


my hesitation really happen at full throttle , pedal all the way to the floor

thanks

HAILERS

Well, I almost learned how to count to ten by ROTE: 1 : the use of memory usually with little intelligence <learn by rote>; 2 : routine or repetition carried out mechanically or unthinkingly <a joyless sense of order, rote, and commercial hustle -- L. L. King>
rote[3]
(adjective) 1 : learned or memorized by rote; 2 : MECHANICAL 3a

So I'll repeat what was said in the posts above. The ECU grounds are on TOP OF THE REAR ROTOR HOUSING on top of a boss and held down with a bolt. There are two (2) wires on that ring terminal. The wires are BLACK. Both are BLACK. They are a part of the EMISSIONS HARNESS.

Those wires leave the ECU (just like you read in the fsm) on pins 3G, 2R and 3A. the 2R and 3A are spliced together before the wires reach Ground Terminal 24 (picture in the fsm).

The wire that runs from just inboard of the wiper area to the engine is NOT A ECU wire. Just run that wire from the area of the wiper motor to anywhere you darn well please on the engine. Run it to the intake manifold if it's easier.

I took everything I wrote above out of the 87FSM. The 88 is very similar. Very.

If you look at the wiring diagrams, the EGI and Emission System you'll see the three wires. On a 88 model the ground point is not called Ground Point 24, but is located in the same place, ON TOP OF THE REAR ROTOR HOUSING. Not on the rear side housing but ON TOP OF THE REAR ROTOR HOUSING on a boss.

I jpg'd a picute recently of a rear rotor housing and the boss. It's out there somewhere.

Whatever you do do not attach a ground wire to the chassis of the ECU. That's would be, well......wrong headed.