yoblink17

i have an 87 n/a sport and im trying to get rid of the 3800 rpm hesitation. So im trying to ground the pressure sensor. Is there a diff b/t the pressure sensor, boost sensor, and atmospheric pressure sensor. Which sensor, because i can only find one, and which wire do i ground and do i necessarily need to ground it to the bolt of the radiator?
thanks

HAILERS

It's the one on the right front strut tower. On a 87 N/T it's called a boost sensor. Don't question why, please. It's written that way in the 87 factory service manual. On a turbo they called it a pressure sensor. Go figure.

The atmospheric pressure sensor is located inside the car on the passengers side. Forget it.

The boost sensor has four wires. The one you want to add a ground to, is the one that is brown with a black stripe. Personally I would not pick the radiator. I'd pick a place on the engine block, or in my case I grounded it to the bracket for the boost sensor. The reason I did that is because I took a meter and measured the resistance b/t the single bolt that holds my boost sensor on...and the battery negative post. I read 0.1ohms to 0.2 ohms which was plenty good fine for me.

Note that I did not get rid of the hesitation until I added additional grounds to the ground wires at the ECU.

My other two cars did not need this. Some cars are good, others lemons. It's the ground splices inside the harness that are bad in my opinion. Look at the wiring schematics. See all the brown/black wires in the schematic for the boost sensor, tps, afm, pressure sensor, water thermo sensor. See how the all tie together???? It takes splice points to do that. The splices just ain't good on some cars. You would think you could go to any brown/black wire on a plug, and read the identical resistance. Ain't so....on some cars. My lemon colored car anyway.

SureShot

The basics:
The ECU uses low voltage signals from sensors (like the TPS & the boost sensor).
Most of these sensors have their own ground wires, but if the primary grounds are the least bit weak, the sensor grounds try to carry the noisy spark and alternator loads also. The ECU tries to compensate & goes nuts.
The firewall to bell housing ground just clips on. Replacing it with a heavy gage wire with eyelets & bolts is a good start.
I have also seen improvements by adding a boost sensor mount to engine ground, and another from the spark coil mount to the engine near the alternator.

Relisys190

iTrader: (4)

i am going to try and tackle regrounding my Ecu this weekend. any suggestions? I pretty much have laid the baseline for good grounds in my car they are as follows :
Altenator bracket - Chassis
Upper intake Man. - Chassis
Negitive Battery - Chassis
Each coil pack - engine
Boost sensor - Chassis




I still get hesitation 'slightly' and i prey that with the ecu grounding it will finally disapear. and input/words of wisdom would be great

=Markus

yoblink17

Problem: Here are the colors of my 4 wires- black & white w/ brown stripe, black w/ brown stripe, brown & white w/ blue stripe, brown & red w/ blue stripe.
I tried the brown & white one, but then my car would not stop.
So, which one is it?
thanks

yoblink17

bump

HAILERS

yoblink17

There's something seriously wrong with your wire colors. Attached is a 87 SERIES FOUR schematic showing the wire colors.

Black with a white stripe;;;;;;;;12v power

Brown with a white stripe;;;;;;;;Approx 5 volts ref voltage.

Brown with a red stripe;;;;;;; out put of the sensor to ECU.

Brown with a black stripe;;;;;; ground wire. Could be a pure black wire on some models.

yoblink17

Sweet, i finally found out which one. I tried the black w/ brown stripe and apparently that was it b/c my car is faster now with a full tank of 87 octane gas than what it used to be with a quarter tank of 89.
thanks guys