ECU ground wire questions
 

I am in the process of cleaning and refurbishing the gounds in my 88 TII and I have some questions about the ecu grounds. Specifically, what is going on with the ground at pin 3G? It seems to come out of the ecu as one wire but then diverges into 3 separate wires. Do these 3 wires go to different points on the chassis? Basically, I want to improve the ecu ground that runs from the ecu to the top of the engine (bolts to the vacuum line harness bolt on TII models). I was thinking of running new wires for this ground but I'm worried about that 3 wire bundle at pin 3G. Does anyone know the specifics on this connection? thanks

Technically those wires are converging into a single wire, because...

No, they are ground connections from other components, specifically the shield wires around the O2 sensor, knoock sensor and CAS wiring. You can see this clearly in the ECU wiring diagrams. Go look...

The point where the various wires are joined make a good place to join on your extra ground wires, because the factory crimp isn't that great and would probably be improved with a bit of solder. If you follow all four ECU ground wires (see link below) you'll see there are two of these crimps. Solder a length of wire to each of joints, then join your two new wires together with a ring terminal. Find a handy bolt or nut that's connected to the chassis, clean the paint of the contact area and bolt it down.

https://www.rx7club.com/attachment.p...hmentid=165722

:)

ok, thanks for the info. In S4 diagram there are 4 grounds noted; would I see performance improvements by taping into all 4 grounds or should I just stick to the 2 points you mentioned?

Where are four wires from the ECU that join with the others into two wires. These two wires go into the engine bay and are grounded with one ring terminal to the engine. Once you peel back the tape around the wires at the ECU and follow the wires up the harness it will all be very obvious.

Don't expect any improvements unless there's an existing problem caused by these ground wires.

crimps
 

Ok, so I've finally found some free time to take a look at the ECU grounds. I have found the ground converging crimps you were talking about NZConvertable. I have a quick question though: Take a look at the pic (link below) it looks like there is a grey wire with wire insulation; and the insulation looks like it is connected to the crimp for some reason. What is the purpose of this? This wiring looks very idiotic to me, maybe thats why the circuits suck in my car.

Here is the link to the crimp pic

http://img.photobucket.com/albums/v3...OUNDCRIMPS.jpg

That's one of the shielded wires from either the knock sensor or O2 sensor. The shield works by grounding one end of the shield wire, which is what you see there. It's shown on the ECU wiring diagrams (FSM page 50-25). Make sure those connections stay intact when you add your ground wires.

Ok, thanks NZ. I've soldered new grounds at the crimps and it's made a world of difference. Cured the 3800 hesitation, added lower rpm and higher rpm throttle response. I'll move on to the other grounds next weekend and maybe I'll get some more improvement

Just for clarification...
the new ground wires should be soldered at the crimped joint of pins 3G, 3A, 2R, and 2C?
Could anyone provide a picture of where the joint is? I'm assuming it's inside the cabin, near the ECU?

a picture of the finished product would be better if someone has it.

Any pictures?

i did this to mine yesterday and it eliminated about 90% of the hesitation.

-pull the carpet up

-unbolt and remove the metal plate

-peel about 6-8 inches of the plastic wrap off of the main wire bundle

-take the old electrical tape off of the black wires with brown dots that meet up (there are 2 sets of these wires that meet)

-take a new 10 inch or so piece of 12 guage wire, crimp the ground wires together (black with brown dots) then crimp the new wire to it

-put a ring terminal at the end of the new wire and bolt it to one of the nuts that bolts the ECU to the floorboard

problem solved

What would this thread be w/o a stupid question.Here it is.As far as the new ground wires soldered to the existing crimps should the new 10 gauge ground wire be a single strand wire or a multi strand wire.

i used multi. it shouldnt matter that much. multi is more flexible though. the wire doesnt go that far.

use whatever you have laying around the house. technically a solid wire has more room for current. were not talking about that much current though so it shouldnt matter.

Just a quick question, I'm also new at this. How many of these wires have to be grounded? Is it the same for both the T2 and N/A?

That diagram, is it looking at the backside of the harness or the pin side of the harness?

that diagram is looking at the ECU

Thanks, is that the standard, when the FSM shows a harness it's from the wire side?

youll see a note by it. in the FSM the one shown says "Control unit side". i wouldnt call it a standard.

Ahh, I'll look for that from now on, thanks

Actually it is. Read the introduction to the wiring diagrams and it tells you that all plugs are shown from the wire side.

youre gonna confuse people with wire side. that could mean looking at the wires from the ECU's viewpoint. but i guess you mean looking as if you were the wires. bottom line is, its as if you were looking at the ECU which i already said.

its a rule not a 'standard' GET IT RIGHT! (who cares) :sleep:

What's confusing about "wire side"? It's the side with the wires. Only an idiot could get that confused.

:rofl: Sorry... :D Ahhh, NZ... I usually think you're a bastard but that was hilarious. :rlaugh:

theres 2 ways to take wire side, and there are alot of idiots on this forum.

omg kiss up much? THAT WAS SO FUNNY YOU SAID IDIOT> OMGZORSZ