1996 5S-FE knock sensor functionality

[bcol]

I have a question I'm hoping you guys can answer.

I'm fixing my sister's 1996 m/t Camry. She blew the head gasket, overheated the car real bad, and blew a hole in the radiator. I'm replacing the whole motor rather than dealing with diagnosing the problem and machine work and such. However, the only motor I could find locally was a 1991 MR2 motor -- i.e. no knock sensor. I swapped all of the Camry electronics and manifolds onto the MR2 longblock but the knock sensor is really the only functional difference.

I'm wondering what the car will do if I just don't run it period. Then, if I must use it, where should I put it?

Of course, when I pulled the motor out, the knock sensor was on the back where you couldn't get to it, and a light tug on the wire broke the connector off the back of the sensor. Total budget so far is about $250 ($150 for the motor and $100 for a new radiator) so I'd prefer not to spend that much again on a new knock sensor from Toyota. Please recommend a junkyard or cheaper alternative if you know of one.

Thanks!

[bill buttermore]

Originally Posted by bcol

I'm wondering what the car will do if I just don't run it period.

Not positive about this, but if Toyota's ECM works like other makers, the computer will be looking for a resistance from the knock sensor to let it know there is no noise from the engine. If that is the case, and since you have broken the connector anyway, a possible work-around is to measure the resistance of the knock sensor and replace the knock sensor in the harness with resistors of the same value. The computer will react as if it never hears any knocking sound and provide full spark advance. The problem with this is that you will have no protection against detonation (pre-ignition) and to obtain the best performance from the engine you may need to run premium fuel. You should also be listening carefully when the engine is under load to make sure you don't hear knocking or pinging. Be aware that detonation can damage pistons and cause premature failure of head gaskets.

[chronoti]

or you can leave it open the cel will be on and the ecu will fall in to fail safe mode setting your timing to something retarted like -20 btdc. and effectively get about 75% of the power before.

just hard solder the wire to the sensor and zip tie it somewhere where it wound be moving around too much prolly close to where it was on the other engine.

[bcol]

Alright, that might make sense. I tried this last year when swapping a 4A-GZE into my MR2, and of course broke the knock sensor when I looked at it wrong, so I left it unplugged and the car pulled all timing at WOT and made no power (slower than the stock 112hp motor even though it was getting regular boost). I thought it might make less difference on the camry motor.

I was assuming (last year) that since it was a one-wire sensor, the ECU didn't apply any voltage to the knock sensor, instead it just measured the voltage generated by the piezoelectric microphone. I figured an unplugged sensor would just register zero knock. But if the sensor is powered and the signal is generated by a change in resistance, causing a change of current, then that would make more sense. This way theoretically I could just ground the sensor to anything in the engine bay and it would register zero knock.

I'm not too worried about detonation given that this is a pretty low-performance motor, but I will be careful.

Thanks for the help!! Much appreciated!