defroster problems: idle speed & not stalling
11-15-2004, 01:33 PM
#1
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Car: '82 trans am (w/ t-top)
Engine: 5.0L 305 H
Transmission: automatic
defroster problems: idle speed & not stalling
When the defrosters are on the idle speed will not go down and if the engine is cold I'll pull away from a stop sign and the engine will die. What could cause this?
11-20-2004, 11:54 AM
#2
Mav,
It sounds like two different issues, possibly related.
First, the LG4 (E4ME Quadrajet) used a high idle speed solenoid to slightly increase idle RPM when the air conditioning compressor is on. If set properly, the solenoid will maintain an idle just slightly above the normal idle with the compressor running. With the solenoid energized and compressor off, however, the idle RPM may be 150-200 RPM higher than the normal curb idle.
When in the DEFROST position, the AC compressor is enabled so that the incoming air is dehumidified before being heated to defog the windshield. In cooler conditios, the AC system may not have enough low side pressure to keep the compressor from cycling off, so the idle speed will be higher.
The best thing to do is set the curb idle correctly, then set the high idle solenoid position to the correct specification with the AC compressor running. It doesn't get any better than that.
Secondly, the fact that you experience stalling on acceleration may be due to a general lean condition, either from improper adjustment or a failing accelerator pump. Once again, at the carburetor, set the mixture control solenoid to specifiactions and make sure the TPS voltage is correct. Once those are correct, verify the operation of the accelerator pump.
It sounds like two different issues, possibly related.
First, the LG4 (E4ME Quadrajet) used a high idle speed solenoid to slightly increase idle RPM when the air conditioning compressor is on. If set properly, the solenoid will maintain an idle just slightly above the normal idle with the compressor running. With the solenoid energized and compressor off, however, the idle RPM may be 150-200 RPM higher than the normal curb idle.
When in the DEFROST position, the AC compressor is enabled so that the incoming air is dehumidified before being heated to defog the windshield. In cooler conditios, the AC system may not have enough low side pressure to keep the compressor from cycling off, so the idle speed will be higher.
The best thing to do is set the curb idle correctly, then set the high idle solenoid position to the correct specification with the AC compressor running. It doesn't get any better than that.
Secondly, the fact that you experience stalling on acceleration may be due to a general lean condition, either from improper adjustment or a failing accelerator pump. Once again, at the carburetor, set the mixture control solenoid to specifiactions and make sure the TPS voltage is correct. Once those are correct, verify the operation of the accelerator pump.
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