FAA Fc

whats up everyone, im a newbie with this. i own a rx7 '86 gxl n/a and i need help figuring out why it begins to bog every time i hit 4000 RPMs

Red_Rotor

iTrader: (3)

4k rpms or 3800 look carefully check ur main ground wire to ur ecu. its under the upper intake manifold attached to a bolt on drivers side top

Aaron Cake

iTrader: (1)

Fix your grounds:
http://www.aaroncake.net/rx-7/grounding.htm

FAA Fc

it bogs at 4k the idle goes no further than that... what does it mean if it bogs at 3800? jus curious. thanx for the help

Sgtblue

iTrader: (16)

It's probably happening at 3.8k.

From that link above:
In a car with a relatively modern fuel injection like the RX-7, the chief problem associated with poor grounds is that sensor readings can be effected. All the sensors in the RX-7 are ground referenced meaning that the ECU passes a current through them to ground essentially measuring the voltage drop across the sensor and using it to adjust engine parameters. If another resistance if introduced into the circuit this value changes and thus the ECU sees the wrong sensor reading. The ECT (Engine Coolant Temperature) sensor/water thermo sensor, IAT (Air Intake Temperature) sensor, TPS (Throttle Position Sensor), pressure/boost sensor, atmospheric pressure sensor and AFM (Air Flow Meter) are all essentially variable resistors with the ECU on one side and a ground on the other (this is a great simplification but good enough for our purposes). The O2 sensor and knock sensor both generate their own voltages but are still connected to ground on one side with the other wire feeding the ECU through a shielded conductor. These sensor errors can cause all kinds of drivability problems that range from the common 3800 RPM hesitation, bucking on decel, poor performance or even sporadic CEL (Check Engine Light) illumination

RotaryRocket88

iTrader: (7)

If cleaning up the existing grounds does not work, some have had success by splicing into the ECU ground wires at the ECU connectors, then running them to ring terminals nearby. If this is done, it is very important to be sure you're grounding the correct wires. The FSM fuel and emissions section & wiring diagrams will be needed.

FAA Fc

thanks everyone for your help i got the problem fixed i appreciate the advice