Active Suspension?
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Joined: Mar 2005
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From: Walton KY
Active Suspension?
I have a '94 LT-1. I have noticed under hard corner entry if I tap my brakes the pedal already feels like it is pulsing as if the ABS is active. No "active" lights show up on the DIC. It does not matter if ASR is on or not. The last curve into one of my shops has this sweet cambered 90 turn then about 150' later is the street into my shop. Almost every time I cook into this turn I feel the pulse. I know it is not the ABS as I am not pushing pedal hard enough to engage ABS and I never hear the ABS pump.
Is there some kind of pitch and yaw control hidden somewhere?
Is there some kind of pitch and yaw control hidden somewhere?
Team Owner
Joined: Dec 1999
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The ASR system has a lateral accelerometer located behind the CD head unit that provides input to the ASR.
Depending on what input the ASR gets, it can either close the throttle, retard ignition timing or apply braking pressure to the front or rear wheels or any combination of these. Detecting a slide as you might see from oversteer, the ASR system may be doing something to help correct the car but not turn the "ASR Acrive" light on.
But with ASR turned off, the system would not react to any of the inputs from either the accelerometer or wheel speed sensors.
Depending on what input the ASR gets, it can either close the throttle, retard ignition timing or apply braking pressure to the front or rear wheels or any combination of these. Detecting a slide as you might see from oversteer, the ASR system may be doing something to help correct the car but not turn the "ASR Acrive" light on.
But with ASR turned off, the system would not react to any of the inputs from either the accelerometer or wheel speed sensors.
Melting Slicks
Joined: Mar 2005
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From: Northeast FL
Just another thought...on occaision slightly warped rotors will cause a pulsation feeling as the pads hit the high and low spots. You can't see the variance in the rotor face because it's so slight but you could try a run out gauge on the rotors and check them. If it's real bad you can notice it if you jack the car up and spin the tires. They won't slowly come to a stop but rather "jerk" to a stop. That's kind of over stated but it's hard for me to describe.
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From: Walton KY
Originally Posted by jwt1603
Just another thought...on occaision slightly warped rotors will cause a pulsation feeling as the pads hit the high and low spots. You can't see the variance in the rotor face because it's so slight but you could try a run out gauge on the rotors and check them. If it's real bad you can notice it if you jack the car up and spin the tires. They won't slowly come to a stop but rather "jerk" to a stop. That's kind of over stated but it's hard for me to describe.
Definitley not warped rotors. It only does it when off the throttle. It did it today coming into the shop and I swear I think I heard the ABS pump this time because I was paying more attention. I usually drive with the ASR off. If it does it, it only happens for a split second. I am no where near impending lock-up or maxium yaw. Just feels a little funny.
Melting Slicks
Joined: Mar 2005
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From: Northeast FL
The rotors were just a thought. Can you pull the fuse on the ASR and try that? It will probably send trouble codes though and God only knows what other computer glitches would show up. Probably lock up the ABS or something. 
1st Gear
Joined: Apr 2005
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From: SE Michigan
Originally Posted by dchildress
I have a '94 LT-1. I have noticed under hard corner entry if I tap my brakes the pedal already feels like it is pulsing as if the ABS is active.
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From: Walton KY
Originally Posted by v8chuck
You're right: the ABS is active. Above some measured lateral acceleration threshold (my SOTP estimate is ~0.7 g and up), the ABS controller preemptively limits brake pressure to the rear wheels to help to avoid oversteer.
This seems to be the culprit. It is a little annoying, but not too intrusive. And now I have my answer...I am outta here
