CEL Hell (1999 Camry)

[lanciat]

Riddle me this, nation members:

Patient: 1999 Camry, 75K miles, 2.2 liter engine. Air/fuel ratio sensor replaced at 45K miles, ECM replaced at 53K miles, oxygen sensors replaced at 63K miles.

Symptom: CEL on, hard starting, rough diving and occasional stalling. Showing both CEL codes P0171 (Bank 1 too lean) and P0170 (Bank 1 too rich). Common causes for the two codes are H2O2 sensor and MAP sensor.

Action: As oxygen sensors were recently replaced, I suspect MAP sensor. I test it, and it is indeed bad. New MAP sensor installed.

Result: Miraculously, the CEL light clears itself. I enjoy one perfect start, and one trouble-free drive.

New symptoms. I restart the car, and experience the same poor start as before the MAP sensor change. The car will barely hold idle, and engine runs rough. CEL comes back on, and car is throwing off the following CEL codes:
P0171 (Bank 1 too lean)
P0105 (MAP circuit malfunction)
P0115 (engine coolant temperature circuit malfunction)
P0120 (throttle position sensor circuit malfunction)
P1130 (fuel air metering control (I assume air/fuel ration sensor).

When I clear the CEL codes by removing the negative battery cable, I again enjoy one perfect start and trouble-free drive. On restart, however, I experience the familiar hard starting and rough running, and the CEL illuminates again.

Thoughts? Any help would be really appreciated.

[JohnGD]

Take an ohmmeter and measure the resistance of the coolant temperature sensor. It's the 2-wire deal near the coolant outlet (not the 1-wire temp gauge sender). See Autozone's free repair guide (with registration) on temp-resistance chart.

How's the condition of the wiring harness?

[carsrus]

I think the intake gaskets are shot. Your getting tons of lean/rich codes. Did you change the PCV?

You might wanna spray some carb cleaner on all the vacuum lines and around the intake to check for vacuum leaks.

But judging by your last comment, the comp might have conked out again. Or you might have a ground/wire issue somewhere.

[lanciat]

Thanks for the input. After reading the comments above, my thought is that simultaneous failure of four sensors (throttle position, coolant temperature, air-fuel ratio and MAP) is unlikely, and that a harness failure or bad ground(s) is the likely culprit. The ECM could have gone bad again, as well, although the one code that the car is not throwing off at the moment is the ECM failure code.