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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Common intake air measurements at "normal" idle should be around 5-9 g/S, with 5 being common at a hot idle in gear (650-ish RPM) to a hot idle in neutral/park (950-ish RPM).
The 1227165 ECM architecture used one-byte (8-bit) data words to define parameters, addresses, and functions. That system allows numeric values from 0 (all bits off) to 255 (all bits on). The definition tables in the ECM ROM translate those values from 0 to 255 g/S. Thus, the minimum cannot be 10-something g/S.
If would be helpful to measure the MAF output voltage from the "C" terminal at idle, which should reveal about 700-800mV (0.70-0.80V). It would also be useful to measure that voltage with the ignition on, engine off. My suspicion is that the MAF may be outputting a signal with zero flow, or something in the circuit is bleeding voltage to the input of the ECM (terminal B12).
Be sure they provided you with a 1986-1989 V-8 MAF. The V-6 versions were different (FM output), despite what some interchanges and the internet might say.
Be sure they provided you with a 1986-1989 V-8 MAF. The V-6 versions were different (FM output), despite what some interchanges and the internet might say.
#10 Thanks for the post! I did install the DelphiMAF #AF10320 (Year 2022 production). See: https://www.thirdgen.org/forums/tech...t-ok-then.html. It fits perfectly. However, car ran overly rich and stumbling at idle. Figured out that the DelphiMAF has a voltage range different than my 1989 OEM Bosch. It seems to stop at 0.80v at the bottom of the scale and won't go further down. The OEM was at 0.60-0.65 at warm idle (800-750 rpm). That added up over 20% fuel!!!! It seems like the voltage scale is off by about 0.12-0.10 volt on average. It's worst at idle since it won't go under 0.80volts. Threw the old MAF on and the car runs smooth and BLM are decent, no code. The higher the air flow, the less impact the voltage offset has.
Just wanted to share my experience.
I'll try to keep the old MAF for now but if it starts acting up again, I won't have choice. That means retuning MAF tables, Open Loop and PE-WOT using AFR gauge. Lots of work you say?... hahah
UPDATE: Just ran an airflow test on the DelphiMAF. With no airflow, it is stuck at 0.80volts. This is definitely an inconvenience to say the least. The OEM BOSCH has a voltage of 0.04volts with no air flow. That means that for a stock LB9 305 it will mess-up idle big time with OEM tune. I'm not even sure I can tune the MAF table since the DelphiMAF reaches 0.80 volts at 850RPM idle. Between 750-850 rpm warm idle it is stuck at 0.80 volts. MAF tables would have to be retuned starting at 850 RPM (0.80volts) and let the BLM/INT compensate under 850 rpm. WOW!
You would have to get a MAF volt reading by back probing the ECM or the MAF connector. I bet you it's the same problem. If you have a '88 GTA L98 AT, most likely you have a $32B mask with BIN AKXX. MAF table #1 would look like this:
As you can see, a small variation in voltage output from the new MAF compare to the old MAF could cause a big g/sec variation at idle. Let's say your L98 is supposed to be around 0.60v-0.65v at warm idle 700rpm (6.80-7.4g/sec) and it's now reading 0.85v, that would = 10.03g/sec. It translate into 35% delta. This is just an example to show the magnitude of the problem.
Be sure they provided you with a 1986-1989 V-8 MAF. The V-6 versions were different (FM output), despite what some interchanges and the internet might say.
I don't believe Delphi makes a MAF for V6 '86-'89. But I could always be wrong
Delphi makes one for V8 '85 #AF10328
I don't believe Delphi makes a MAF for V6 '86-'89. But I could always be wrong
Delphi makes one for V8 '85 #AF10328
well it definitely seems to be a problem. I returned my Amazon purchase and went with one from summit which clearly stated for 5.7.
I will update my results. Appreciate all the info being given . Odd that the readings could be so much different, maybe a call to Delphi might be in order.
well it definitely seems to be a problem. I returned my Amazon purchase and went with one from summit which clearly stated for 5.7.
I will update my results. Appreciate all the info being given . Odd that the readings could be so much different, maybe a call to Delphi might be in order.
No problem
Which one did you get from Summit?
I got my Delphi from RockAuto
Sure, post your results
Cheers
Remember that I did ask for voltage measurements. That would have been very helpful. There is no way of knowing now.
According to the information directly from Summit, that MAF is used on any thirdgen F-car. https://www.summitracing.com/parts/D...0/applications It clearly indicates applications for V-6 AND V-8 engines. I personally know that to be completely incorrect. Someone in their accounting and marketing offices forgot to check with someone in their engineering office (presuming they have one) of they would not have made this blatant error.
I've seen this error repeated on many sites, many times. Apparently, someone is not doing homework and simply parrots the information which they "read on the internet" which, of course, is always true.
Remember that I did ask for voltage measurements. That would have been very helpful. There is no way of knowing now.
According to the information directly from Summit, that MAF is used on any thirdgen F-car. https://www.summitracing.com/parts/D...0/applications It clearly indicates applications for V-6 AND V-8 engines. I personally know that to be completely incorrect. Someone in their accounting and marketing offices forgot to check with someone in their engineering office (presuming they have one) of they would not have made this blatant error.
I've seen this error repeated on many sites, many times. Apparently, someone is not doing homework and simply parrots the information which they "read on the internet" which, of course, is always true.
does everything with these cars need to be so damn hard! I have a million things to move on to and get stuck on somethings that should be so simple. But i guess that's why where all here!!!!
I'm just thinking out loud here, but let's say you wanted to keep the stock tune and use the 0.80v minimum MAF. Could you install a voltage dropalyser box thing on the signal wire and "correct" the output?
does everything with these cars need to be so damn hard! I have a million things to move on to and get stuck on somethings that should be so simple. But i guess that's why where all here!!!!
I'm just thinking out loud here, but let's say you wanted to keep the stock tune and use the 0.80v minimum MAF. Could you install a voltage dropalyser box thing on the signal wire and "correct" the output?
Take a look back at Post #2. It was mentioned that the MAF could be outputting excessive voltage at zero flow, OR that something in the circuit could be pulling it up.
I'm just thinking out loud here, but let's say you wanted to keep the stock tune and use the 0.80v minimum MAF. Could you install a voltage dropalyser box thing on the signal wire and "correct" the output?
That's possibly Teepee-Eye-speak for a divider network using three resistors. That may provide disappointing results on the other end of the scale unless an A/A scalar is used. Then again, the electronics on the MAF itself should already take care of that if someone has done the homework. Apparently no one does that any more. A guy could rig a pair of A/D - D/A converters (like THIS and THIS) in line to scale the MAF signal, but why? It should already have been done on the MAF itself. It used to be done that way...
UPDATE: Just ran an airflow test on the DelphiMAF. With no airflow, it is stuck at 0.80volts. This is definitely an inconvenience to say the least. The OEM BOSCH has a voltage of 0.04volts with no air flow. That means that for a stock LB9 305 it will mess-up idle big time with OEM tune. I'm not even sure I can tune the MAF table since the DelphiMAF reaches 0.80 volts at 850RPM idle. Between 750-850 rpm warm idle it is stuck at 0.80 volts. MAF tables would have to be retuned starting at 850 RPM (0.80volts) and let the BLM/INT compensate under 850 rpm. WOW!
That only reinforces my point. My take on that is that the MAF output may be FM and the sellers are counting on the ECM recognizing an RMS value of that FM output. It doesn't work that way in the real world. If you have an oscilloscope (even an old, slow one) check the MAF output signal with that. The results should be very helpful. Most FM MAFs, even the most recent versions, are at best WAY under 10 kHz.
The Wells SU145 MAF I have on my '86 does mere millivolts in KOEO mode, which works amazingly like the stock Bosch 0280 213 004 units used to work. If you understand the operating scheme of a hot-wire MAF, the output cannot be zero since there will be some heating current required to maintain the sensor temperature due to radiant loss, even at no air flow. Bosch got that number as low as they possibly could to make the MAF as accurate as possible.
I contacted Delphi to get some clarification. As you could see they say this model number does not work for V6 and has a minimum airflow of 3.5 G. A little encouragement for my delivery today
I contacted Delphi to get some clarification. As you could see they say this model number does not work for V6 and has a minimum airflow of 3.5 G. A little encouragement for my delivery today
Interesting.
Does it mean 3.5g/sec at 800mv is the minimum? Does it mean the stock 305 TPI has less than 3.5g/sec at warm idle 850rpm and the MAF is maxed out? I doubt very much.
Let's see what you get.
Thanks
Last edited by SbFormula; Mar 8, 2023 at 10:51 AM.
As you could see they say this model number does not work for V6 and has a minimum airflow of 3.5 G. A little encouragement for my delivery today
Thanks for the reply. It seems that the sales department finally found out that there is an engineering department, and then actually asked the relevant questions. The engineering department pointed out that the V-6 MAF is NOT the same as the V-8 MAF. You're lucky to have an '88, because the 1985 V-8 MAF is also different from the 1986-89 version, and yet I see a LOT of catalogs and internet listings showing one MAF from 1985 onward.
I wonder how many times they use the message "It looks like there may be an error on the catalog you are looking at."
Interesting.
Does it mean 3.5g/sec at 80mv is the minimum? Does it mean the stock 305 TPI has less than 3.5g/sec at warm idle 850rpm and the MAF is maxed out? I doubt very much.
Let's see what you get.
Thanks
I believe that we cannot assume that output. The message only states that the MAF can read down to 3.5g/S. We have no idea what the MAF output voltage is at that flow level. We know that your MAF seems to have a minimum of 800mV, but there could be manufacturing variation. That's why I asked about the voltage measurement with zero flow and at idle.
FWIW, a 305TPI system with an replacement TFT style MAF has outputs like this:
We need to have the measurements before analysis can begin.
I also remembered that since you're above the St. Lawrence, some correction factor might need to be applied. That 8.35 g/S on Long Island could be 11.45 g/S in Ontario.
I also remembered that since you're above the St. Lawrence, some correction factor might need to be applied. That 8.35 g/S on Long Island could be 11.45 g/S in Ontario.
For my part, I’m at sea level. Atlantic ocean in my back yard. Get MAP readings 103-104 all the time. 102 when I was in Montreal was a great day!!!!
I believe that we cannot assume that output. The message only states that the MAF can read down to 3.5g/S. We have no idea what the MAF output voltage is at that flow level. We know that your MAF seems to have a minimum of 800mV, but there could be manufacturing variation. That's why I asked about the voltage measurement with zero flow and at idle.
FWIW, a 305TPI system with an replacement TFT style MAF has outputs like this:
We need to have the measurements before analysis can begin.
I will try to take those measurements when I receive the new one
I believe that we cannot assume that output. The message only states that the MAF can read down to 3.5g/S. We have no idea what the MAF output voltage is at that flow level. We know that your MAF seems to have a minimum of 800mV, but there could be manufacturing variation. That's why I asked about the voltage measurement with zero flow and at idle.
FWIW, a 305TPI system with an replacement TFT style MAF has outputs like this:
We need to have the measurements before analysis can begin.
okay so received the new MAF and pretty much the same problem as soon as I take my foot off the gas it immediately drops to 10 point something so you may be 100% correct about interference or something of that nature would you be able to point me in the right direction of how to give me the readings you suggest I take
okay so received the new MAF and pretty much the same problem as soon as I take my foot off the gas it immediately drops to 10 point something so you may be 100% correct about interference or something of that nature would you be able to point me in the right direction of how to give me the readings you suggest I take
Monitor B12 while idling (voltage)
Check voltage on B12 when KOEO (0 air flow)
If those measurements were taken directly at the MAF connector, you now have TWO bad MAF sensors. You may want to check the ECM grounding since the analog ground voltage floating around shouldn't do that. But even at that, the analog ground voltage isn't varying enough to explain the insane MAF output from the second new unit.
If those measurements were taken directly at the MAF connector, you now have TWO bad MAF sensors. You may want to check the ECM grounding since the analog ground voltage floating around shouldn't do that. But even at that, the analog ground voltage isn't varying enough to explain the insane MAF output from the second new unit.
i probed about a foot off connector.
what should I be seeing?
Last edited by george88gta; Mar 9, 2023 at 07:43 PM.
ok so that would be green on maf. I get 0.826v running and 1.489v key on.
My bad!!!!!
It's not KOEO. If you do that you will get a voltage that is not relevant. If I remember, my new Delphi MAF was also reporting 1.4??v KOEO (back probed and datalogger matched). Old MAF was reporting 2.610V with KOEO.
The way I did it was:
KOEO, I probed the ALDL fuel pump primer to turn on the MAF and took readings. That's how I got 800MV with no airflow on Delphi. I used forced air to make the MAF voltage varied. Delphi's voltage would go up but never under 800mv. Did the same with the OEM MAF and I got 40MV with no air flow. When engine running, I got the readings from the MAF and datalogger (They both matched). New MAF was stuck at 800mv and old MAF was varying normally 550-650mv on warm idle.
I did not take any readings on the other wires, just the dark green.
Sorry for confusion.
Last edited by SbFormula; Mar 9, 2023 at 08:26 PM.
You see on the chart, in closed loop, idle, the BLM is maxed out at 112 (dark blue) and INT working to pull out fuel at 107 (red). I was jerking the gas pedal, that's the TPS (light blue). You see the MAF voltage (green) flat at 800mv where it should be around 600mv. Again, slapped the old MAF on and car ran fine with BLM around 128.
My old MAF was not sending any signal that's why I ordered a new one. But after testing the entire circuitry, the old MAF started sending a signal and everything has been working fine since then. So that's how I was able to compare new Delphi with OEM Bosch. I'm still running the old OEM MAF and the car is smooth. Just did a ride today!
The Delphi MAF is not compatible IMO. Flawed from factory.
If, while running at idle, assuming all things being equal, your Delphi MAF gives you 862mv and the old MAF 700mv, that is a 27% increase in airflow for the ecm.
...It's not KOEO. If you do that you will get a voltage that is not relevant. If I remember, my new Delphi MAF was also reporting 1.4??v KOEO (back probed and datalogger matched). Old MAF was reporting 2.610V with KOEO.
SB - Good catch! I neglected to mention that there is about a 2-second window to measure the MAF output voltage at KOEO condition.
And the second new MAF is still reporting 860mV at idle, which can't be very good on a stock 350 unless the idle is quite a bit higher than normal.
Well just picked up a Cardone maf. Now reading 5grams.
I believe I hear a small leak in that air snorkel connected to the throttle body maybe my cause of lean condition.
are there any aftermarket manufacturers?????????
