Egr "sensor"

[doug7x]

OK, folks...I went through the same egr bs as most of you. (code 53, clean out the valve & passages, verify operation, etc). I'm still getting the 53 fault code. Sometimes it goes away for a week...sometimes a day or two. (it has been re-setting by itself...I never disconnected the bat to clear the code) I KNOW the egr is working....I can see it open & close as I operate the throttle linkage, & when I push on the diaphram, the engine almost dies. SO....WHAT is telling the ECM that the egr isn't working? Is there a limit switch somewhere? Does the ECM use O2 sensor data to see the egr problem? I'm kinda lost on this. '95 1.0 MT OBD1 (still getting 53-55 mpg combined, & runs fine with 190,000) ...Thanks

[lancekilgore]

clear the code and see if it comes back.

[sas95]

I've got an OEM manual for '95s and I've got a '95 1.0L 5-speed manual.

There is no trouble code 53. The highest code is a 51 ... and that's the EGR circuit code. (Actually, if you really are reading '53', you might have an ECM problem.)

Sounds like you've done thorough testing of the EGR valve. Since the engine almost dies, I think this rules out plugged up EGR passageways.

Here's some descriptive info. The exhaust gas recirculation solenoid vacuum valve is engine control module controlled. System voltage is applied to the EGR SV vavlve from the main relay. When the driver in the ECM closes, the EGR SV valve is activated. DTC 51 will set if the follwing conditions are met:
1. System is operating in closed-loop operation.
2. Difference of MAP sensor between when EGR SV is 'ON' and when 'OFF' is less than a calibrated value.

With a scanner hooked up and driving along, I've seen that the EGR SV is closed whenever the throttle is closed. Once you start to open the throttle while driving, the EGR SV opens. Then as you depress the gas pedal more and more, there is a MAP value at which the EGR SV closes again. So, when the engine is heavily loaded, the EGR system is closed again. This is all just engineering info of interest, and may not help you at all.

However, here's the Diagnostic Aide stuff:
Closely check all vacuum hoses to the throttle body fuel injection unit and the EGR valve. Also check the MAP sensor vacuum hose for leaks or restrictions. In "Closed Loop" operation with the EGR enabled, the ECM will periodically turn "OFF" the EGR SV valve. If the corresponding manifold pressure change is less than a calibrated value, the ECM determines that a fault exists in the EGR system and sets DTC 51.
An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, imporoperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.

I suggest you replace with new vacuum line the line from the TBI to the MAP sensor, the line from the TBI to the pressure transducer, EGR SV and EGR valve. New vacuum line is cheap and shouldnt take too much time. This should rule out a vacuum line leak.

Have you tested the pressure transducer? If this is not working right, this could explain your problem. You need a vacuum gauge to check it.

[doug7x]

You're right...it's a code 51...I have no idea why I said 53. Anyway, I did disconnect the bat the other night & the check engine light has not come back yet...maybe thats it. As far as the connections & vac hose condition, everything looked good. I'll post again if it comes back...thanks, folks...Doug