glock

i have a problem with the maf sensor.. i was not getting power to the burn off on the maf ...so i replaced the burn off relay still no power.. when i pull off the burn off relay i get 14.1 volts with engine running .when i use 2 jumper wires to the relay i lose (blk 900 d12 burn off control )if i take that jumper to the battery neg terminal the relay closes and sends power to the maf .... does that sound like a bad ecm ?

customblackbird

iTrader: (15)

ive been throwing the burnoff relay code with 2 diff maf's and ive replaced the relays as well.... idk wat the prob is either. the burnoff relay isnt activated until the motor is turned off and its only activated for a sec. i would try looking at the wires and connections. idk about the ecm. i could be

glock

yeah i just checked the black 900 d12 wire from the relay to the ecm and i have continunity...and checked according to my wiring schmetic d6 tan wire and d3 blk/wht wire look to be my only grounds to ecm and they have continunity to ground ..its just when i put a load on my blk 900 and 12v i lose my blk 900 ground ...does the maf sensor it self send any signal that controls that blk 900 wire to the ecm or does the ecm or prom itself control that ground wire?

glock

bump

glock

also car runs like crap when the maf is plugged in ...runs good when disconnected....and 1 other thing my ignition coil went bad small crack along the tower which shot a spark from under the boot and was arching to itself ..just wondering would that of sent voltage through a ground and to the ecm?

customblackbird

iTrader: (15)

hmm hard to say, i kno the burnoff circuit is in the MAF, the relay is external. so if its running bad with the MAF connected and better when its not connected i would swap out the MAF, it takes like 30sec and if it doesnt work just return the new MAF, dont get it dirty tho. i doubt the arching would haveaffected the ECM. it woulda just grounded itsself. ur car still runs so ur ECM hasnt been affected.

glock

the problem is anytime you buy electrical parts they wont take it back i really dont think its the maf... i could be wrong... its the ecm thats not grounding d12 to make the coil in the relay close for the burnoff relay

customblackbird

iTrader: (15)

yea but it still shouldnt run better with the MAF unplugged or out.its suppose to run like **** wit it unplugged. im throwing the same code as u but my car runs fine im just getting the darn code. thats a tell tale sign that the maf is bad. i had the prob with that and i took the MAF out and replaced it wit one from my 86ta and the prob went away but then came back a month or so later. really? im alowed to bring my MAF back as long as it doesnt look like it was used.

plug in a new MAF and see what happens. or get a friend wit a ECM and swap it out. either way ur looking at one expensive part... i need to figure out whats wrong with mine too. its annoying bc this code never goes away and i hate looking at the check engine light.

glock

funny thing is im not throwing a code or a check engine light the only time i throw a check engine light or code is if i disconnect the maf sensor

Vader

Instead of replacing a MAF, diagnose it. There are some things to check in the burnoff circuit, and since the engine runs poorly with the MAF connected, you should also check the MAF signal while the engine is running.

MAF Operational Tests - 1986-89 Delco/Bosch Analog Units

Whenever a sensor or device is suspect, the first thing to check are the circuit connections. In the case of a MAF sensor, there are multiple devices involved with successful operation, including the MAF power relay, MAF burn off relay, ignition switch and fusible links, fuses, ECM, and finally the MAF itself.

The MAF should have a five wire connector.

1. Terminal A is a system ground connection, and usually has a black/white wire attached;
2. Terminal B is the MAF signal ground. It usually has a black wire. If all ground lugs, ground connections, and the ECM grounds are intact, this should be effectively the same as the system ground;
3. Terminal C is the MAF signal output, and usually has a dark green wire;
4. Terminal D is a used to initiate a burn off cycle in the MAF. There should be a dark blue wire connected there;
5. Terminal E has a red wire for the +12VDC power supply. There should be voltage present whenever the MAF power an burn off relays are operating properly.

Expose the MAF and its connector so you can test voltages by back-probing the connector. With the ignition turned off for safety, measure the resistance from both the ‘A’ and ‘B’ terminals to the negative battery post. There should be 0 ohms, or at most 0.5 ohms due to circuit wire resistance. Any resistance greater than that can indicate a poor ground connection in the circuit tested. Disconnect the meter, turn the ignition to ON, and test terminal ‘E’ for supply voltage. You should read the same voltage as you would at the battery. Lower voltage indicate a possible MAF power relay or other circuit connection problem. If the grounds and supply voltage are satisfactory, connect the ‘C’ terminal and system ground, and start the engine. Allow the engine to warm and reach a normal idle RPM. At an RPM of 800-900, the MAF should output a signal of between 700-800mV on a 305 engine, and between 750-900 mV on a 350 engine. Outputs which are significantly lower can indicate a leaking connection between the MAF and throttle body and its duct work, or any other intake leak, such at the PCV system, CCV, failing gaskets, and others. If the MAF output is substantially lower or higher than the nominal output, the sensor may be dirty, failing electrically, or the engine RPM is not within the proper range.

MAF Burn Off Operation and Testing

1. The MAF burn off relay should have a constant 12VDC supply (battery voltage) on both the 'E' terminal and 'C' terminal (via the orange wire).
2. The 'B' terminal should switch to ground through the ECM output transistor within 20 seconds of the engine shutting off and the oil pressure switch opening. The ECM awaits the loss of power on its 'B2' terminal (Fuel Pump Voltage) before it can initiate the burn off cycle.
3. When the ECM commands a burn off cycle, the relay should close, and 12VDC is switched to both the 'D' terminal on the MAF Sensor itself, and the 'D' terminal on the MAF power relay.
4. Power is routed through the N.C. contacts of the MAF power relay to the MAF sensor to enable the MAF sensor electronics package. This is critical, since the MAF sensor must report a signal back to the ECM to prove a good burn off cycle. This is also why a failing MAF power relay can cause a MAF burn off error.
5. Upon receiving all these signals, the MAF sensor hot wire is heated to full incandescence, and the MAF sensor reads the hot wire current at full. This causes the MAF sensor to report a full, 5VDC saturated (non-duty-cycling) signal to the ECM.
6. Upon receipt of this signal, the ECM registers a complete MAF burn off cycle, ungrounds the 'B' terminal of the MAF burn off relay, and is satisfied.

NOTE: Any interruption of the cycle will cause an error, and subsequent error code. This includes marginal relay contacts, poor connections and grounds at any point, and intermittent operation of the auxiliary oil pressure switch, since any voltage from the oil pressure switch will indicate to the ECM that the engine is not shut down, effectively terminating the cycle.



Other things to check:

1. The MAF power relay should have a constant 12VDC supply (battery voltage) on the 'A' terminal (via the orange wire).
2. There should be a 12VDC supply whenever the ignition is ON at the 'B' terminal (via the black/pink wire).
3. The 'E' terminal should have a good ground at all times through the black/white wire.
4. Both the normally closed and normally open contacts of the relay (from terminals 'E' to 'A' for N.O., and 'D' to 'A' for N.C.) must be operational and reliable (see above).