I've pretty much finished grounding everything in the bay(or cleaning the grounds, that is), but I had a quick question pertaining to Aaroncakes instructions for the secondary ground on the boost sensor. His tutorial says that in s4's the ground wire on the harness is black/brown, but on inspection today, there's a black-with yellow strip(what i think is the ground) and then a brown-dotted with blue. So which is the ground, before i cut anything? Thanks in advance.

 

A 87 engine did not have any of the colors you mention. It seems your on the wrong sensor.

A 87 has a brown/white (ref voltage), black/white (12vdc pwr), brown/red (output to the ECU) and either a pure black or a brown/black (ground wire).

There's a free download of the 88 FSM on this site which shows the gnd as a pure black wire.

 

The boost sensor ground fix only applies to 86 models anyway, so don't bother.

 

Although it probably doesn't help you since you don't have an 86... this may help somebody. Learn from my lameness.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/pressure-sensor-ground-3500-hesitation-fix-572799/

 

I've a 87 non turbo converted to a turbo.

Prior to becoming a turbo car, if had a hesitation when secondary injectors came online.

After reading a thread by Rxster, I regrounded or added grounds to the ground wires AT the ECU.

These wires are black wires and are in pins 2C, 2R, 3A, 3G.

If one unwraps the harness of the small plug, he'll find the two black wires from 3A and 3G come together with the shield of the 02 sensor output wire (2D). At that point I soldered a new wire to those three and also added the one from 2C and 2R. Put a ring terminal on the other end of the new wire and bolted it to one of the studs that hold my ECU in place.

On THAT car, if I remove that NEW wire that's bolted to the ECU mount stud, it will start the hesitating once more. Put the ring terminal back on and the hesitation goes south.

My other two cars don't have this. One a 86 n/a and the other a 87 factory turbo car. It's anybodys guess why this works on some cars and not others or even why it had to be done to one out the three I own. Got me.

That said, the pin 2A mentioned above goes to each sensor in the engine bay plus the ATP in the car. All the gnd wires for those sensors are spliced together in the EM harness and terminate at 2A going into the ECU.

And the factory service bulletin that added the gnd wire to the boost/pressure sensor had an explanation as to WHY it was being added. The gnd was actually an additonal gnd for the AFM and this was the logical/easy place to do it (remember, all sensor gnds are spliced together inside the EM harness). On the 87 car mentioned above, I added that extra pressure sensor gnd.

If you just gnd the chassis of the ECU..............all you did was ammuse yourself. My ECU's will work just fine laying on a piece of carpet with no chassis gnd at all.