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Resident asshole
Corolla
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There really isnt a crank position sensor at all. The engine doesnt know when its BTDC, but it doesnt need to as the ignition is done with the distributor and injection isnt a sequential system.
 

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actually there is a sensor in the distributor so that the coil and injectors pulse at the correct time, its a camshaft position sensor. its not like a system that has both cam and crank sensors, since there is no crank sensor, but there is a cam position sensor in there. iirc the rotor has 4 tangs and its a hall effect sensor.

double checked the manual, yes it is in the distributor. it should be the 6 cavity plug on the outside of the distributor housing. if you want i can try and type up the testing procedure outlined in my factory manual for the 93 prizm.
 

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Resident asshole
Corolla
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iirc the rotor has 4 tangs and its a hall effect sensor.
Actually its an inductive pickup not a HALL. Operation is similar, but works in a different method.

However, even that doesnt tell the ECU at what direction the cam is pointing, it just gives a signal to the ECU to spray fuel and to operate the ignition. I think the ECU counts every 4 times to spray fuel.
 

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Actually its an inductive pickup not a HALL. Operation is similar, but works in a different method.

However, even that doesnt tell the ECU at what direction the cam is pointing, it just gives a signal to the ECU to spray fuel and to operate the ignition. I think the ECU counts every 4 times to spray fuel.
i know it batch fires pairs of injectors. so that would be correct i think.
yes, it just tells the pcm that the engine is spinning and at what speed so that it can time fuel sprays and sparks, not the direction...since the engine wont turn backwards. its assumed that if the sensor is seeing motion that the engine is spinning one way.


now i wonder, on obd2 7afe/4afe how do they set cylinder misfire codes if theres no crank position sensor? is it unable to set specific cylinder misfire codes? i'd look it up but my car and manual are both obd1.
 

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OBD-2 can and does set specific cylinder misfire codes. How, I don't know, but I've had to clear out one of mine.
so somehow the PCM must know the position of the crank or cam, and since the 7afe/4afe are almost identical from obd to obd2 then i suspect that obd *afe's must also know the same thing. :confused:
 

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Owner of much Obsolete
1986 Corolla GT-S
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2,286 Posts
I'm under the impression it fires all 4 at once.

and the OBD-1 is quite far from OBD-2
I don't think Toyota fired all the injectors at once ever in any of their EFI systems, except maybe the early 22R-E's in the 80's or something. I know on the 4M-E (Their first EFI system) they fired in batches of 3.

1993-1994 models, all engines (4A-FE and 7A-FE) are batch fired in 2 groups.

1995 models, the 7A-FE is sequentially fired and not grouped, 4A-FE is still batch fired.

1996+ models, all engines (4A-FE and 7A-FE) are sequentially fired, not grouped.

Jeff
 
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Premium Member
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I don't think Toyota fired all the injectors at once ever in any of their EFI systems, except maybe the early 22R-E's in the 80's or something. I know on the 4M-E (Their first EFI system) they fired in batches of 3.

1993-1994 models, all engines (4A-FE and 7A-FE) are batch fired in 2 groups.

1995 models, the 7A-FE is sequentially fired and not grouped, 4A-FE is still batch fired.

1996+ models, all engines (4A-FE and 7A-FE) are sequentially fired, not grouped.

Jeff
very good information to know, i did not know about the difference from year to year when dealing with how the fuel is injected.
 
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