A while back there was a hesitation thread about sc400's during take off. Now I was talking to a ecm tuner guru who said that heat sheilds and other metalic vibration and rattle noises can cause the knock sensor to retard that timing on the car.

So i was thinking, to anyone that has a diagnostic tool, will it tell you what the knock sensor is doing while you drive the car? OBD1 and OBD2 are different I'm sure, my 95 is obd 1, and the diagnositic port is on the intake manifold, and another is under the left side of the dash. My Snap on scanner will not hook up with toyota 1 adapter, something just doesn't quite fit correctly, the adapter is too large.

Anyone want to check this out?

 

I'd like to find out if that is true or not but don't have the equipment.

One observation that I don't know is related to that topic or not is that my SC400 seems to drive stronger in really hot weather than it does in cooler weather.

My second observation, which is more related to that topic, is that with my SAFC2 I notice once in a while the knock sensor reading will spike to a value over 200 and then fall right back to zero. It's reading from knock sensor #1 too.

 

Thats the type of thing I'm talking about. Faulty readings! Good information!
Now if the ecu see's a reading like 200 on the knock sensor, that whole trip the timing will most likely be retarded. I don't think an obd-1 computer is advanced enough to go back to full timing, I think it would enter a "safe-mode" It may even last longer than the whole trip.

Sometimes my car runs unbelievable well for 20 seconds after startup, and then all the sudden it feels like i lose 20hp. I know my car doesn't run as well as it used to.

Future plans are to replace the cats, change my battery cable connections and replace my grounds. Jibbby mentioned using a current/voltage regulating device which I wouldn't mind doing if the new cables and connectors don't do the trick.

 

I'm having the exact same problems, what did you figure out?

 

Well nothing definite yet.

But I will tell you this. I was playing around with a new snap-on scan tool. I was in the mode where you can see what all the sensors are doing real-time.

I have no exhaust on the car right now. The loudness when I rev the car (due to open headers at least) is enough to set the knock sensor off.

I've replaced the motor with a 27K mile motor. So that means 27K mile cats and 27K mile 02 sensors.

I also picked up a spare ecu to try out...

Once I get the car all buttoned back up...I'll report back with more info.

 

This is interesting, I was talking to one of my friends about this exact subject. That on harder launches, the car seems to really retard timing.

It'd be interesting to see where this goes. Keep us posted on what you find out.

 

any update on this?