Hesitation, bogging and stalling
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Joined: Dec 2001
Posts: 1,997
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From: Bartlett, IL
Car: 92 ZR-1
Engine: LT-5
Transmission: ZF-6
Axle/Gears: SuperDana 44 4.10
Hesitation, bogging and stalling
These three are probably the more frequent issues with owners of the C4 LT-5, particularly when they modify the motor.
Typically, the first things done are porting of the intake (plenum and injector housings) along w headers and exhaust.
Hesitation occurs after decel, bogging usually from standing start. The stalling can occur when freewheeling to a stop. The more rapid the decel, the more likely the stalling. One other thing w freewheeling is an oscillation of the idle as u roll to a stop. I’ve also observed it on a slow crawl, in neutral, and putting a load on the motor such as turning the steering wheel.
I’ve done my own changes like setting Min Air properly, and modifying SA for idle too low or too high along w increasing Idle SA. Increased the MPH for Idle control. Lowered PropGain v gm/sec at 0 gms/sec. And I recently increased MAX Airflow for Idle from 16gm/sec to 20 because I noted in the logs, that at idle I was exceeding 16. Again due to increased airflow from the modifications. MAP/RPM boundries have also been bumped from stock. AE PW v MAP delta also increased.
Recently, I believe I’ve been able to really control these issues better. There are three parameters in the $D0/A Masks that pertain to TPS% for C/L Idle, TPS% for IAC CONTROL, and then the IAC TF/MIN TF v MPH tables.
Thought I would put this out there and see what the experience of the group here has been w similar issues on various motors.
comments?
Typically, the first things done are porting of the intake (plenum and injector housings) along w headers and exhaust.
Hesitation occurs after decel, bogging usually from standing start. The stalling can occur when freewheeling to a stop. The more rapid the decel, the more likely the stalling. One other thing w freewheeling is an oscillation of the idle as u roll to a stop. I’ve also observed it on a slow crawl, in neutral, and putting a load on the motor such as turning the steering wheel.
I’ve done my own changes like setting Min Air properly, and modifying SA for idle too low or too high along w increasing Idle SA. Increased the MPH for Idle control. Lowered PropGain v gm/sec at 0 gms/sec. And I recently increased MAX Airflow for Idle from 16gm/sec to 20 because I noted in the logs, that at idle I was exceeding 16. Again due to increased airflow from the modifications. MAP/RPM boundries have also been bumped from stock. AE PW v MAP delta also increased.
Recently, I believe I’ve been able to really control these issues better. There are three parameters in the $D0/A Masks that pertain to TPS% for C/L Idle, TPS% for IAC CONTROL, and then the IAC TF/MIN TF v MPH tables.
Thought I would put this out there and see what the experience of the group here has been w similar issues on various motors.
comments?
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