Cascade Crew

[turbo_jimi]

These were the 2 codes that the 86 TA were showing on Saturday. Went to TGO and found the following info posted which I think will be helpful:

Code 33 MAF Tests

The MAF is a sinking input device. In other words, the ECM supplies a current-limited 5VDC supply to the MAF sensor, and the MAF will ground that signal down closer to 0VDC at lower than maximum detected air flows. If the logic circuit ground connection to the MAF is not continuous, or is not properly grounded, the MAF cannot pull down the 5V signal as it is designed to do. Thus, the MAF ground must be at the same potential as the ECM ground - The system MUST have good grounds everywhere. Similarly, if the MAF signal circuit suffers from poor connection or continuity, the signal may be higher than intended. All wiring and connections must be intact.

The MAF burnoff system can also cause this code to set if the MAF burn off relay or circuit has problems with resistive leakage, bridging connections from corrosion, poor grounding, etcetera.

You really don't need anything more than a good volt/ohm meter to diagnose the system. With the ignition ON and engine not running, make sure the correct voltage and grounds are present at the MAF terminals.

Test the MAF Signal Voltages
The MAF signal circuit (Terminal C) should be less than 0.3V with the ignition on and engine not running.
Disconnect the MAF electrical connector and test the voltage again. There should be a 5VDC reference voltage from the ECM.
Verify that the TPS voltage is between 0.47 and 0.61VDC.
Test for voltage in the MAF burn off circuit (Terminal D at the MAF) while the ignition is on, engine off or running. Any voltage present can cause the MAF signal at the ECM to be too high.

Diagnosis
A code 33 is set when the ECM has detected an intake air flow above 45 grams per second (about 2.2 volts) for one second when the engine is first started or at any time when the TPS is less than 1/4 throttle and RPM is less than 2,000.

If you discover problems in the voltage or grounding checks, re-seat the connectors at the ECM and check all the circuit grounds. Make sure the connector at the MAF itself is intact.

If there is a problem with the 5VDC reference voltage from the ECM, re-seat the ECM connectors and/or test for the correct voltage directly at the ECM terminal B12. If there is not 5VDC source (± 0.6V) present at the ECM connector, the ECM itself may have a problem.

With the ECM connectors clean and properly connected, if the reference voltage is significantly higher than 5VDC, there may be a problem with the other wiring shorting to that circuit on the vehicle.

If you are able to read voltage at the MAF burnoff circuit, remove the MAF burnoff relay and retest. You can even run the car in this mode, but will eventually set a "36" code for the burnoff failure.

If all voltages are correct, and all grounds and connections are intact, the MAF itself may have problems. A MAF failure causing a "33" is uncommon, but I suppose it is possible. It is generally more common to find circuit problems or a TPS adjusted too low.

Connecting a 12VDC power source to the fuel pump test terminal ("G" terminal of ALDL) will provide power to the MAF sensor, and the MAF signal circuit should create a low voltage (less than 250 mV) signal to the ECM. Monitoring the MAF signal voltage in this mode and wiggling the circuit connectors and wiring may allow you to detect any intermittent problems. Similarly, an erratic MAF signal with the engine running may indicate wiring or connector problems.

If you determine the MAF has a problem, the MicroTech 491018 units are decent replacements. They are identical to the old Wells SU-145 units.

[aaron_sK]

Ohh man, I hurt my brains reading that.

Bottom line: Get a burnoff relay at the JY, and blow the maf out with electronic cleaner (I've got some laying around somewhere). If that doesn't fix it, replace the MAF. The engine backfired enough that we have reason to suspect it is dead.

[turbo_jimi]

amazingly enough, i have electronic cleaner