91' 305 TBI

How hard is it to change the following sensors? .....where are they located?.....and how do I do it? I'm trying to save some money here.

TPS

MAP

EGR Valve

 

Easy, TPS is on the left side of the throttle body, two torx screws.
MAP sensor is hooked to the throttle body vacum port usually on the left side mounted on a bracket over the valve cover. EGR is behind the Throttle body mounted in the intake two nuts and a vacum hose.

all in a easy to change. Be sure to use GM parts only aftermarket just don't cut it in my experience.

Mike

In Bangkok

 

Left side sitting in the car?...or standing in front of it? Not to be difficult, but could you use driver side and passenger side please?

 

Facing the front of the car..

 

why do you need the TPS sensor? did it crap out? make sure you check the voltage before you replace it, it might just need some adjusting

 

EGR Valve - expensive ... to the tune of $70 or more.

EGR valve can usually be cleaned. May also just need a EGR Solenoid ... it controls the vacuum on the valve ... much cheaper $30.

Check the EGR first. Start car, at warm idle, reach in and push the EGR valve in by hand - if it moves, and the car tries to die, it should be functioning properly. So then try checking the vacuum on it, and cleaning it out.

Here is the AllData info for a 1990 TBI 305 if it helps:

EGR SYSTEM CHECK

CIRCUIT DESCRIPTION :

The EGR valve is controlled by a normally open, Pulse Width Modulated (PWM) solenoid. The ECM powers the solenoid off, to allow vacuum to flow to the EGR. The ECM turns the solenoid on to prohibit EGR operation.
The duty cycle is calculated by the ECM based upon information from the coolant temperature, MAT, TPS, and MAF sensors. The engine rpm and Park/Neutral switch also affect EGR. There should be NO EGR flow in Park/Neutral, below TPS Calibrated value, or at wide open throttle.
With the ignition on and engine not running, the EGR solenoid is de-energized. The solenoid should be energized if the diagnostic terminal is grounded with the ignition on and engine off.

TEST DESCRIPTION : The numbers below refer to circled numbers on the diagnostic chart.



This tests the solenoid value to determine if it is capable of closing off the vacuum from the EGR valve. The vacuum can bleed off slowly (this should not be considered as a fault).
As soon as backpressure is present at the EGR valve, the bleed portion, in the valve, should open and allow the valve to move to its heated position.
The EGR will be inoperative if the Park/Neutral switch is mis-adjusted, or faulty. Use a computer diagnostic tool to check the Park/neutral switch.
NOTE: Once the test sequence is completed, clear codes and verify NO "SERVICE ENGINE SOON" light exists.

INCORRECT EGR OPERATION :



If too much EGR is flowing at idle, cruise, or cold operation, any of the following conditions could exists:
The engine dies after cold start.
The engine stalls on deceleration.
The vehicle surges during cruise mode.
Rough idle.
If too little or no exhaust gases flow, the combustion chamber temperature may increase under acceleration or heavy load conditions. These conditions could cause:
Detonation (Spark Knock).
The engine to overheat.
The emissions test to fail.

 

Well, my EGR and TPS is good. It's my MAP Sensor that has a little voltage jumping going on while under throttle. But I don't know how that would affect performance, since it's obviously not enough to send a code.