MAF burn-off/power relay pinouts needed
12-22-2013, 05:56 PM
#41
Racer
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Attempt to clarify:
There are 4 signals in play.
1. The 8 bit unlimited airflow signal which you refer to as ACUTAL maf.
2. The 16 bit display value which you refer to as CALCULATED maf.
3. The default airflow signal which is calculated from tps, rpm, IAC + offset.
4. The max maf vs rpm table value which is used to limit the display value as a function of rpm.
Under error free conditions assuming the unlimited airflow (1) is below the max maf vs rpm limit table value (4), the display value and unlimited airflow values will be very similar, neglecting filtering and scaling influences.
If the unlimited airflow (1) exceeds the max maf vs rpm table value (4), the display value (2) will be limited according to the limit value (4) and begin to deviate from the unlimited airflow value (1) as flow increases.
If a MAF error is detected, the display value (2) will be replaced by the default airflow calculated value (3) and will also be subject to limitation by the max maf vs rpm value (4).
So when you see the display value drop relative to the unlimited airflow value, you are either seeing the effect of the limitation without an error condition, or the result of the default airflow calculated value replacing the display value along with the effect of the limitation with an error condition present.
Since you seem to be getting a code 33 repeateadly. I have to assume that you are seeing the latter (display value being replaced by default airflow value due to error). Since the default airflow value is apparently lower than the actual airflow according to your description, the resulting pw is causing the lean condition.
If you're getting a code 33, its due to the unlimited airflow exceeding the threshold. It is possible that the bin you are currenly running has been modified and the Code 33 thresholds may have been changed, so your mileage may vary.
Easiest fix is to de-sensitize the code 33 error setting conditions in the tune, if you think you can trust your MAF and tps readings directly.
There are 4 signals in play.
1. The 8 bit unlimited airflow signal which you refer to as ACUTAL maf.
2. The 16 bit display value which you refer to as CALCULATED maf.
3. The default airflow signal which is calculated from tps, rpm, IAC + offset.
4. The max maf vs rpm table value which is used to limit the display value as a function of rpm.
Under error free conditions assuming the unlimited airflow (1) is below the max maf vs rpm limit table value (4), the display value and unlimited airflow values will be very similar, neglecting filtering and scaling influences.
If the unlimited airflow (1) exceeds the max maf vs rpm table value (4), the display value (2) will be limited according to the limit value (4) and begin to deviate from the unlimited airflow value (1) as flow increases.
If a MAF error is detected, the display value (2) will be replaced by the default airflow calculated value (3) and will also be subject to limitation by the max maf vs rpm value (4).
So when you see the display value drop relative to the unlimited airflow value, you are either seeing the effect of the limitation without an error condition, or the result of the default airflow calculated value replacing the display value along with the effect of the limitation with an error condition present.
Since you seem to be getting a code 33 repeateadly. I have to assume that you are seeing the latter (display value being replaced by default airflow value due to error). Since the default airflow value is apparently lower than the actual airflow according to your description, the resulting pw is causing the lean condition.
If you're getting a code 33, its due to the unlimited airflow exceeding the threshold. It is possible that the bin you are currenly running has been modified and the Code 33 thresholds may have been changed, so your mileage may vary.
Easiest fix is to de-sensitize the code 33 error setting conditions in the tune, if you think you can trust your MAF and tps readings directly.
12-24-2013, 02:39 PM
#42
Racer
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I still have to do a test drive, but I have installed a rheostat on the maf signal wire to bring the reading down slightly. Not exactly a perfect solution, but it will tell me if it is just a slightly higher reading that is setting off the code 33. If it continues to throw the code 33 with the reading below the threshold, I know I have other things to look at, such as a spike from a bad connection I cannot see on my recordings.
12-24-2013, 04:58 PM
#44
Race Director
I got these conditions for setting an error code 33 from the EPROM firmware in the ECM for my '86:
Engine is first started
** or ** TPS < 14.8%
RPM < 3200
Fuel pump voltage > 10.0VDC
Mass Air Flow sensor output > 2.2VDC (45 gm/sec) on pin B12
All conditions must be met for > 0.96 seconds
Basically it says that if the RPM is less than 3200 and the TPS is less than 15% then it's not physically possible for the air flow to be more than 45 gm/sec.
Usually this is caused by a bad connection in the MAF connector (corroded pin). ECM pin B12 could also have a bad connection. It could also be a broken wire. The ECM has a pullup resistor on pin B12 and it will show maximum air flow if the connection is bad.
You could try unplugging the MAF (the car will run just fine without it connected). Also you could short the MAF output pin in the connector to ground (MAF disconnected of course). That will set an error code 34, but at least you'll know the connection from the MAF to the ECM is good.
Engine is first started
** or ** TPS < 14.8%
RPM < 3200
Fuel pump voltage > 10.0VDC
Mass Air Flow sensor output > 2.2VDC (45 gm/sec) on pin B12
All conditions must be met for > 0.96 seconds
Basically it says that if the RPM is less than 3200 and the TPS is less than 15% then it's not physically possible for the air flow to be more than 45 gm/sec.
Usually this is caused by a bad connection in the MAF connector (corroded pin). ECM pin B12 could also have a bad connection. It could also be a broken wire. The ECM has a pullup resistor on pin B12 and it will show maximum air flow if the connection is bad.
You could try unplugging the MAF (the car will run just fine without it connected). Also you could short the MAF output pin in the connector to ground (MAF disconnected of course). That will set an error code 34, but at least you'll know the connection from the MAF to the ECM is good.
Last edited by Cliff Harris; 12-24-2013 at 05:01 PM.
12-24-2013, 10:02 PM
#45
Racer
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I got these conditions for setting an error code 33 from the EPROM firmware in the ECM for my '86:
Engine is first started
** or ** TPS < 14.8%
RPM < 3200
Fuel pump voltage > 10.0VDC
Mass Air Flow sensor output > 2.2VDC (45 gm/sec) on pin B12
All conditions must be met for > 0.96 seconds
Basically it says that if the RPM is less than 3200 and the TPS is less than 15% then it's not physically possible for the air flow to be more than 45 gm/sec.
Usually this is caused by a bad connection in the MAF connector (corroded pin). ECM pin B12 could also have a bad connection. It could also be a broken wire. The ECM has a pullup resistor on pin B12 and it will show maximum air flow if the connection is bad.
You could try unplugging the MAF (the car will run just fine without it connected). Also you could short the MAF output pin in the connector to ground (MAF disconnected of course). That will set an error code 34, but at least you'll know the connection from the MAF to the ECM is good.
Engine is first started
** or ** TPS < 14.8%
RPM < 3200
Fuel pump voltage > 10.0VDC
Mass Air Flow sensor output > 2.2VDC (45 gm/sec) on pin B12
All conditions must be met for > 0.96 seconds
Basically it says that if the RPM is less than 3200 and the TPS is less than 15% then it's not physically possible for the air flow to be more than 45 gm/sec.
Usually this is caused by a bad connection in the MAF connector (corroded pin). ECM pin B12 could also have a bad connection. It could also be a broken wire. The ECM has a pullup resistor on pin B12 and it will show maximum air flow if the connection is bad.
You could try unplugging the MAF (the car will run just fine without it connected). Also you could short the MAF output pin in the connector to ground (MAF disconnected of course). That will set an error code 34, but at least you'll know the connection from the MAF to the ECM is good.
I have also ran the car with the maf unplugged, and shorted the input to ground, to check out the wiring and ecm.
Last edited by nobodycls; 12-24-2013 at 10:08 PM.
12-25-2013, 07:56 PM
#46
Racer
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Code 33 is GONE! I tried everything under all conditions and could not get it to set, so I am officially saying that the code is being set by a slightly high maf signal due to either the aftermarket maf, the cam, or the fairly short, unrestricted induction.
Now, on to the other issues, lol. I am suspecting the injectors that I was told by you guys not to install ( I know, I know, trying to be cheap)are giving me my last problems with driveability. I get a random hesitation, or stumble, and sometimes it is like a switch being flipped - I will take off, and it seems to have no power, and then VROOM it takes off like normal. It will also occasionally have a rough idle, and sometimes even stall. It will usually get a little worse after warming up, but not much. Whenever it does this, the O2 reads lean, and the integrator value will rise to 160 or so. The fuel pressure is good at all times, no codes are being thrown, and the egr system is working as it should. I had to unclog 3 of the injectors when i got them (wouldn't even click), and they all pass an ohm test, but I have no way to test the impedance. The injectors are the stock 24# units, is it normal for them to act up intermittently? Any other tests I could do to confirm injectors as the problem? I plan on using fic when I get new injectors.
Now, on to the other issues, lol. I am suspecting the injectors that I was told by you guys not to install ( I know, I know, trying to be cheap)are giving me my last problems with driveability. I get a random hesitation, or stumble, and sometimes it is like a switch being flipped - I will take off, and it seems to have no power, and then VROOM it takes off like normal. It will also occasionally have a rough idle, and sometimes even stall. It will usually get a little worse after warming up, but not much. Whenever it does this, the O2 reads lean, and the integrator value will rise to 160 or so. The fuel pressure is good at all times, no codes are being thrown, and the egr system is working as it should. I had to unclog 3 of the injectors when i got them (wouldn't even click), and they all pass an ohm test, but I have no way to test the impedance. The injectors are the stock 24# units, is it normal for them to act up intermittently? Any other tests I could do to confirm injectors as the problem? I plan on using fic when I get new injectors.
Last edited by nobodycls; 12-25-2013 at 08:00 PM.
12-26-2013, 02:22 AM
#47
Melting Slicks
What a great thread. This is mostly over my head but certainly better than the "parts swap" troubleshooting you see so often.
12-26-2013, 07:55 AM
#48
Racer
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I have gotten so much great help on here. I like to figure things out, and hate buying a part without knowing for sure it is bad. My troubleshooting skills had gotten a little rusty, and I am learning the systems better now than I ever had before, which is great. My next step is datalogging and learning to tune, so I can make adjustments on my own when I rebuild.
12-28-2013, 10:13 AM
#49
Racer
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No suggestions on injector testing, huh? Today I plan on retesting the wiring again for possibly losing power to one bank or the other intermittently, and pulling and checking injectors for clogging and cleaning them if they still pass an ohm test and operate, then flush the rails and lines and replace the filter on the frame rail. - that is, if I feel well enough, feeling kind of bad today.
12-31-2013, 10:05 PM
#50
Racer
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Looks like I'll be getting some new injectors for the new year - I have a few that won't quit leaking and have a funky spray pattern, even after I tried backflushing them a few times. These should be the ones I need - http://fuelinjectorconnection.com/sh...?productid=195
My intake has the 24# injectors and that is what the prom is set for. Would there be any advantage (other than price) to going with 19 or 22 # injectors and getting the prom reflashed?
My intake has the 24# injectors and that is what the prom is set for. Would there be any advantage (other than price) to going with 19 or 22 # injectors and getting the prom reflashed?
01-03-2014, 03:21 PM
#51
Racer
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Ok - I just called and ordered some new injectors from fic,(super nice guy!) they should be here next week sometime. Once installed, I will see if that clears up the last of my problems. I think I will investigate a possible bad u-joint while I wait for the injectors to arrive.