I'd originally started into this in the MeMyMod section, but perhaps I can spark some interest (pun intended) in here.
I have recently acquired an '87 Celica GT. ST-162, 3S-FE, manual tranny.
The engine knocks noticeably under normal driving.
I've got the timing set dead-on at 10 BTDC warm, at idle, with the diag jumper in.
Tonight, I actually went in and watched the ignition advance with my timing light as I ran the RPM up and down. At idle, with the diag jumper out, the ignition is around 15 BTDC. Then, I reach over and slowly open up the throttle (reeeeal slowly):
The timing stays where it is until about 1,400 RPM (or about 5 degrees of throttle opening), and then it suddenly jumps to damn near full advance (it has a few degrees left for once it gets up around 3,000 RPM, but I mean it when I say it jumps straight from 15 BTDC to about 30 BTDC.) At that point of course I start to hear the knocking.
Some notes:
1- The jump in advance is exactly co-incident with the throttle position switch moving out of the IDL position. (this engine doesn't have a true throttle position sensor, just two switches. It's either fully closed, wide open, or somewhere in-between.) If I manually open the IDL contact, it advances immediately. If I hold the IDL contact closed, it never advances.
2- There is no MAP sensor on the '87 3S-FE. All it knows is RPM, air volume, and temperature.
3- I have replaced the following:
- Coil
- Rotor
- Cap & wires
- Spark plugs
- Air flow meter
4- The engine is hard to start when cold. (cold = it hasn't been running within the past couple of hours, regardless of outside temperature)
5- The vehicle passed an Ohio emissions test last month.
At this point I'm really stumped, and I'm getting close to buying a new ECU.
I have recently acquired an '87 Celica GT. ST-162, 3S-FE, manual tranny.
The engine knocks noticeably under normal driving.
I've got the timing set dead-on at 10 BTDC warm, at idle, with the diag jumper in.
Tonight, I actually went in and watched the ignition advance with my timing light as I ran the RPM up and down. At idle, with the diag jumper out, the ignition is around 15 BTDC. Then, I reach over and slowly open up the throttle (reeeeal slowly):
The timing stays where it is until about 1,400 RPM (or about 5 degrees of throttle opening), and then it suddenly jumps to damn near full advance (it has a few degrees left for once it gets up around 3,000 RPM, but I mean it when I say it jumps straight from 15 BTDC to about 30 BTDC.) At that point of course I start to hear the knocking.
Some notes:
1- The jump in advance is exactly co-incident with the throttle position switch moving out of the IDL position. (this engine doesn't have a true throttle position sensor, just two switches. It's either fully closed, wide open, or somewhere in-between.) If I manually open the IDL contact, it advances immediately. If I hold the IDL contact closed, it never advances.
2- There is no MAP sensor on the '87 3S-FE. All it knows is RPM, air volume, and temperature.
3- I have replaced the following:
- Coil
- Rotor
- Cap & wires
- Spark plugs
- Air flow meter
4- The engine is hard to start when cold. (cold = it hasn't been running within the past couple of hours, regardless of outside temperature)
5- The vehicle passed an Ohio emissions test last month.
At this point I'm really stumped, and I'm getting close to buying a new ECU.