Toyota 4af engines

The Chilton shows a 2 wire,non heated sensor for the 91if I read it right. Advance auto parts shows a 2 wire non heated Bosch as the OEM one. I got one that was in a piece of pipe that was in the trunk. Looks just like the 89 single wire but it is a 2 wire deal. I will try to find a plug to fit the sensor but if not its chop cut rebuild time. The sensor in the piece of pipe looks to be the one from the 91 but the plug is gone and the wires are cut super short. Like it was ripped off and not unplugged. I am going to use shielded wire if I can find it or un pin something from the 89 harness long enough to work and not cut. The diagram shows a wire (black?) as the signal wire and it also runs to the "check conector". Another is shown to go to ground. The ecu pin locations are "10b " for the signal, "24b" for the ground that splices also with "13b, and 26b" Am I on the right track here? I also have a sensor that is unplugged because its broke off. It is under the distrib.,in the thermostat housing,facing the radiator. I'm just hoping it isn't something efi related because I can't figure out what its for.

The connector on the thermostat housing is one of the temp senders. I don't know which one. If it's the ECU one, that's important. Look at the wire color and find it in the schematic. Otherwise, looks like you're making progress. The O2 sensor does go to the Diagnostic Connector and to the ECU. 2 wire sensors have a signal and signal ground, so that fits with your schematic. I put a 2 wire sensor on the Sportster so I'd have a good ground (1 wire sensors ground through the exhaust), but no current drain for a heater circuit (3 and 4 wire sensors have a heater circuit).

I have a decent looking single wire from the 89. Think it would hurt to run that one wire to the signal pin and try it? New sensor is $64 if I remember right. I looked all through the sensors listed on advance's web site. Not a one looks like what I got. I did hook up the one wire sensor under the distro. and one on the other side of the thermostats' flow in the goose neck. To me one senses radiator coolant temp(the broken one?) and the other senses block coolant temp,sends info to the ecu and the ecu does its thing with fans and fuel tables,timing and such. I could be wrong,just a guess. If it wont crank and run I will got to a pull a part and try to find one. Dealers are way high. I paid 6 bucks for the washers that go on the cold start line bolts. 4 thin copper washers,but i had to have them. I hope to get it cranked thursday night. I still need to put in the axles and efi gas tank. Why did toyota put the clamp on the pipe end in the filler neck for the gas tank where you can't get to it unless you drop the rear crossmember? I dread putting the efi tank in.

A 1 wire sensor should probably work. Is it the bolt on kind with an oval plate? That's what Toyota used most of the time back then. They are a little hard to find, but O'Reilley's carries them now. I think Bosch makes one.

If I recall, the connector on the thermostat housing is the switch for the fan. If you go back over my posts, you'll note I said that the ECU does not control the cooling fan. A complicated series of relays does.

O'Reilley's also carries those copper crush washers.

Yeah, its the 2 bolt oval plate one wire. Looks like its close to new actually. I hope to get it together after sunrise. First thing is the gas tank then the last of the wiring,hoses and stuff. Axles then turn the key and hope it will fire without a fire. I need to fix the exhaust but that will have to wait for another day. For now it's a straight dump at the cat flange. I thought it a good idea to remove the cat rather than plug off the old egr pipe and get the cat fire hot. It will be a track only car anyway soon. Ga isn't an emissions check state yet so I can get away with it for a while driving it to work. I will have to start going to O'Reilley's even though its across town. Advance is closest to me so I go there by default. I only go to auto zone as a last resort because either they dont have it, it wont fit, or it doesent work dealing with them. I got to many bad "rebuilt" starters and alternators form them that went out in no time. It still bothers me not knowing what that sensor does. I am eventually going to put in some cheap mechanical gauges for oil pressure, water temp, and voltage so I may not even need a new one if that is what it is. I looked all thru the chilton but have seen nothing in the diagrams or listed in there. I will figure it out in time...Will let you know if it runs later..peace

Read the resistance on the sender. If it is open, it's the switch for the fan relay. Not the fan directly, of course, as that would burn the switch out.

I have a question somewhat related to this thread so I am bringing it back from the dead.

Can you throw a 7afe block and head complete into an 89 corolla and just swap over the 4af intake with carb and the exhaust from the 4af and expect it to run?

My buddy did a "heart puffer" on his 91 civic wagon where he pulled his 1.5 dual point injected motor and tossed in a much newer 1.6 long block and just swapped his intake/ exhaust.

I want to do something similar to this corolla. It has low compression and probably wants a head gasket. Not worth it in my opinion. I just want to toss in a 1.8 7afe and swap over all the intake/ exhaust form the current 4af and roll.