SEFI Cars Auto To Manual Swap & That Damned O2 Sensor Plug

[87gtVIC]

Right. So Pin 30 now goes through your manual transmissions neutral switch, then through your clutch mounted switch (gray plug with two wires (yellow with blue AND Black with white)) and ultimately your black with white wire leads back to pin 46 . Sound correct.

[87gtVIC]

You still have starting solenoid? For A9P, connect pin 30 to "S" term on it.

I believe that is how the car (1987 Crown Victoria) is wired from the factory as per my EVTM. "S" terminal is the start terminal correct? If so then yes already done. I wired the clutch pedal safety switch (black connector plug) within this path. Power to starter solenoid "S" terminal goes through my clutch mounted safety switch first.

This is all with a A9P Mass Air computer.

[ZephyrEFI]

Right. So Pin 30 now goes through your manual transmissions neutral switch, then through your clutch mounted switch (gray plug with two wires (yellow with blue AND Black with white)) and ultimately your black with white wire leads back to pin 46 . Sound correct.

Yep, back through signal return.

Sent from my SM-G960U using Tapatalk

[OX1]

I believe that is how the car (1987 Crown Victoria) is wired from the factory as per my EVTM. "S" terminal is the start terminal correct? If so then yes already done. I wired the clutch pedal safety switch (black connector plug) within this path. Power to starter solenoid "S" terminal goes through my clutch mounted safety switch first.

This is all with a A9P Mass Air computer.

So are you thinking that takes the place of an auto's nuet start switch
in that A9P circuit? Sounds reasonable, for starting at least.

[87gtVIC]

So are you thinking that takes the place of an auto's nuet start switch
in that A9P circuit? Sounds reasonable, for starting at least.

Precisely. This is how the mustang is wired according to the 1989 evtm I have.

This brings about other issues though....I dont believe the computer (A9P) will not know I am in neutral unless I have my foot all the way depressed on the clutch pedal. Or....it will always think I am in neutral..depends on where I put the clutch pedal mounted nss in line. I took it directly off the ignition switch before it branches out anywhere else. Hmm.

[87gtVIC]

I think this is what I need to do. Only down side is the car will only start in neutral. Not a huge problem. This should solve any hanging idle problems when coming to a stop as ground will go to pin 30 of a9p computer when clutch is pushed in as well as when shifter is pushed in independently of each other.

*I should have wrote in NGS NOT NDS*



Just unsure if any weird feed back loop of power will cause any issues with this schematic I drew up.

Any concerns?

Again, I think this would solve any hanging idle issues once my receive when converting an auto car to 5 speed while retaining the auto computer on a car that is not a mustang.

[87gtVIC]

Revelation..Stay tuned.

[87gtVIC]

If it is to be believe that pin 30 of the computer (A9P in this case but same for others such as A9L etc of this ford 5.0 era) is strictly looking for a ground to determine when the transmission is in neutral/park then all one would need to do snip pin 30 at the computer and put one side of the neutral sense switch at the clutch pedal (Gray connector) with one side of the NGS of the manual transmission to it making sure to leave the snipped portion that lead to the starter solenoid no longer connected to pin 30 or anything.just safely covered so it does not ground out on anything.

The other side of the neutral sense switch at the clutch pedal (Gray connector) with the other side of the NGS of the manual transmission and tap into pin 46. This would do it if the below information is accurate:

Let me try to give you an explanation:

Its not that the O2 sensors - or their function - is any different between MT and AT cars, its that the O2 sensor harness is different.

The EEC uses many sensor inputs to determine strategies for engine operation under various conditions. One input the EEC uses to determine idle, and idle down (ie 'dashpot'), strategy is transmission gear. The EEC is 'signaled' by 'grounding' pin 30 so it 'knows' whether the transmission is in gear or not. For MT it uses the NGS (mounted on the top cover of the T-5) and CES (mounted on the clutch pedal) which connects pin 30 to pin 46 (SIG RTN, an EEC internal 'ground'). For AT the NSS is used to signal that it is P or N by using the same circuit that is used to connect the starter solenoid to the ignition switch. When the AT is in P or N pin 30 is grounded thru the internal 'coil' of the starter solenoid.

Ford essentially used two sets of circuits (wires) to deliver the MT or AT signals from the respective transmissions to the EEC processor. Presumably for cost/commonality reasons both sets of circuits are contained within the main EEC harness. The determination of which circuit is used is made via a specific 'jumper' wire. The jumper is different for MT and AT. Ford put the jumper in the O2 sensor harness, therefore there are 'MT O2 harnesses' and 'AT O2 harnesses'. From arms length (and even closer) the MT and AT O2 harnesses appear identical but under close examination of the 8-pin connector where the O2 harness connects to the main EEC harness you would see a difference in the pinout position of the jumper wire. So although we all call this harness the 'O2 sensor harness' it actually contains more functionality than that. Just for the record the 'O2 sensor harness' also contains the wire for the 'low oil' sensor which is mounted on the oil pan and also has nothing to do with the O2 sensor function.

The A9L vs A9P processor issue has to do with the fact that on AT applications the pin 30 ground signal in P or N uses the same wire that is used to supply battery voltage thru the ignition switch to the starter solenoid during START. So during START pin 30 will see battery voltage because the AT transmission 'signaling' circuit is wired that way. But its only wired that way when the AT specific O2 sensor harness is used. I cannot verify that certain processers are 'immune/vulnerable' to having battery voltage on pin 30. I have read that the AT processors (ie A9P, etc) are 'immune' and that MT processors are 'vulnerable' (A9L, etc) to being 'fried' when battery voltage is put to pin 30. That is why it is said that it is OK to use an AT processor in a MT - because in an MT car (with an MT O2 sensor harness) pin 30 does not recieve battery voltage in START, but not visa versa. More importantly though is that when the 'wrong' O2 sensor harness is used (ie an MT harness on an AT car) the EEC will not recieve any signal at pin 30 because the correct jumper for the necessary AT circuit will not be there. And that can/will cause issues with idle and idle down (ie rough idle, stalling, etc). That is why I feel it is incorrect when it is said that all you need to do is use matching processors and O2 sensor harnesses - regardless of the actual trans in the car. For example if you have a car that has an MT and you use the EEC processor and O2 harness from a donor car that was AT although the processor and O2 sensor harness 'match' the processor will not receive the transmission signal at pin 30 because the jumper in the AT O2 harness is incorrect. The best way is always to match the transmission, O2 sensor harness, and EEC processor.

I hope this explanantion was helpfull.

https://www.corral.net/threads/will-...#post-10244134

Latest schematic for my 1987 Crown Victoria application:





I think this is keeping it simple while still having everything work correctly without questionable work arounds I was previously thinking of.

[ZephyrEFI]

Nice! I think you've got it! I wonder if it will be an issue that your pin 30 DOESN'T see battery voltage. I wouldn't guess it will be.

I have mixed feeling about seeing my theory about my having sent power to my pin 30 corroborated. . I guess the computer still seems to work though, so that's what matters.

[87gtVIC]

Nice! I think you've got it! I wonder if it will be an issue that your pin 30 DOESN'T see battery voltage. I wouldn't guess it will be.

I have mixed feeling about seeing my theory about my having sent power to my pin 30 corroborated. . I guess the computer still seems to work though, so that's what matters.

Yes. That is the only part of the whole deal I am unsure of as well.

That power to pin 30 would only be while cranking then it turns to ground through the starter relay. Hard to find any information on what the computer is actually looking for to make these calls.

[ZephyrEFI]

That power to pin 30 would only be while cranking ...

Yeah, I know. But still... It was a new engine first assembly, so I did things like disconnect the coil and crank the engine to get the oil circulating (yes, i also turned the oil pump with a drill). crank it, oops distributor is 180 off, crank it again, fires and dies, crank it again... Makes me nauseous to think about it.

[87gtVIC]

Yeah, I know. But still... It was a new engine first assembly, so I did things like disconnect the coil and crank the engine to get the oil circulating (yes, i also turned the oil pump with a drill). crank it, oops distributor is 180 off, crank it again, fires and dies, crank it again... Makes me nauseous to think about it.

Just act like it never happened. You said you witness no ill effects as of yet so just tell yourself all is fine.

[ZephyrEFI]

Just act like it never happened. You said you witness no ill effects as of yet so just tell yourself all is fine.

Yep, you're right.

[87gtVIC]

I went for first drive in my manual converted 1987 Crown Victoria. I wired in everything according to my latest sketched schematic and everything works perfectly. Not sketched is the cruise dump via the little switch next to the go pedal. That works to. My set up is an A9P in a car that was originally auto and now converted to manual.

[OX1]

I went for first drive in my manual converted 1987 Crown Victoria. I wired in everything according to my latest sketched schematic and everything works perfectly. Not sketched is the cruise dump via the little switch next to the go pedal. That works to. My set up is an A9P in a car that was originally auto and now converted to manual.

Glad to hear it. Should make this and that other thread on O2 harnesses "stickies" somewhere.

[ZephyrEFI]

Awesome, congrats!

I'm waiting on a few more parts (tax money) before I take mine too far.

Sent from my SM-G960U using Tapatalk

[Paul1958]

Its not that the O2 sensors - or their function - is any different between MT and AT cars, its that the O2 sensor harness is different.

The EEC uses many sensor inputs to determine strategies for engine operation under various conditions. One input the EEC uses to determine idle, and idle down (ie 'dashpot'), strategy is transmission gear. The EEC is 'signaled' by 'grounding' pin 30 so it 'knows' whether the transmission is in gear or not. For MT it uses the NGS (mounted on the top cover of the T-5) and CES (mounted on the clutch pedal) which connects pin 30 to pin 46 (SIG RTN, an EEC internal 'ground'). For AT the NSS is used to signal that it is P or N by using the same circuit that is used to connect the starter solenoid to the ignition switch. When the AT is in P or N pin 30 is grounded thru the internal 'coil' of the starter solenoid.

Ford essentially used two sets of circuits (wires) to deliver the MT or AT signals from the respective transmissions to the EEC processor. Presumably for cost/commonality reasons both sets of circuits are contained within the main EEC harness. The determination of which circuit is used is made via a specific 'jumper' wire. The jumper is different for MT and AT. Ford put the jumper in the O2 sensor harness, therefore there are 'MT O2 harnesses' and 'AT O2 harnesses'. From arms length (and even closer) the MT and AT O2 harnesses appear identical but under close examination of the 8-pin connector where the O2 harness connects to the main EEC harness you would see a difference in the pinout position of the jumper wire. So although we all call this harness the 'O2 sensor harness' it actually contains more functionality than that. Just for the record the 'O2 sensor harness' also contains the wire for the 'low oil' sensor which is mounted on the oil pan and also has nothing to do with the O2 sensor function.

The A9L vs A9P processor issue has to do with the fact that on AT applications the pin 30 ground signal in P or N uses the same wire that is used to supply battery voltage thru the ignition switch to the starter solenoid during START. So during START pin 30 will see battery voltage because the AT transmission 'signaling' circuit is wired that way. But its only wired that way when the AT specific O2 sensor harness is used. I cannot verify that certain processers are 'immune/vulnerable' to having battery voltage on pin 30. I have read that the AT processors (ie A9P, etc) are 'immune' and that MT processors are 'vulnerable' (A9L, etc) to being 'fried' when battery voltage is put to pin 30. That is why it is said that it is OK to use an AT processor in a MT - because in an MT car (with an MT O2 sensor harness) pin 30 does not recieve battery voltage in START, but not visa versa. More importantly though is that when the 'wrong' O2 sensor harness is used (ie an MT harness on an AT car) the EEC will not recieve any signal at pin 30 because the correct jumper for the necessary AT circuit will not be there. And that can/will cause issues with idle and idle down (ie rough idle, stalling, etc). That is why I feel it is incorrect when it is said that all you need to do is use matching processors and O2 sensor harnesses - regardless of the actual trans in the car. For example if you have a car that has an MT and you use the EEC processor and O2 harness from a donor car that was AT although the processor and O2 sensor harness 'match' the processor will not receive the transmission signal at pin 30 because the jumper in the AT O2 harness is incorrect. The best way is always to match the transmission, O2 sensor harness, and EEC processor.

I hope this explanantion was helpfull."



https://www.corral.net/threads/will-...#post-10244134

Wow, I wrote all that 10 years ago and people are still using it.

[ZephyrEFI]

Thanks! Yeah, it's almost like a myth. Plenty of people know there's SOMETHING you have to do, but they only know bits and pieces about anything else with it. Very few people know what, how, AND why!

[87gtVIC]

Wow, I wrote all that 10 years ago and people are still using it.

I appreciate it. Helped me out.