92 Grand Am general question?

[alconk]

Car is the 3.3 V6.
1. should the heater core blow hot air or luke warm? Some cars don't get hot even when new..
2. can a 02 sensor make a car idle bad in the open loop? I actually have a code for it but when in closed loop it purs at idle??
3. good one?.... HVAC works fine now but can't figure out why I get heat on the driver's side and cool air out the passenger side I have the factory mannuals and it don't show any blend doors. All you have is the cold/ heat door and the heat/ defroster/vent door. There is one more but can't remember what it controls..

[3100]

1. The amount of heat that you get inside of the car depends on the coolant temperature. If coolant is hot, heater core will be hot and then depends on your setting cold-hot (which controls doors inside of the duct work to mix hot and cold air. Ex: if your setting is at 50% of heat the door inside of the duct work that controls mix of hot air coming from heater core and cold air that is coming from outside will be open 50%. If you set it to 100% hot then the control door inside the duct work will be completely closed for the cold outside air and only heated air from heater core will be allowed to enter inside of the cabin. (this all works if heater core is not clogged)

2. O2 sensor can not make car idle bad in open loop. O2 controls AF (air /fuel) ratio only in closed loop.
Every time engine is started it does not matter if it was driven for 5 hours or 1 min it will always start in an open loop. However, open loop time will depend on the amount of time it takes to heat up o2 sensor. Normally if engine was driven for 5 hours, open loop will be shorter when you start the engine comparing to the open loop time when vehicle was driven for 2 minutes. When is the engine in open loop? At start ups, at WOT (wide open throttle) and when AC is on. At open loop pcm uses preset look up tables for commanding of the injector pulse width (amount of time injector stays on and off) Ex: ect temp is 32 deg F, throttle plate open 0% MAP pressure 29, Air temp coming into engine 35 deg F (so this looks like a cold start and engine is just idling) pcm based on this parameters will adjust injector pw lets say to 4ms

now second ex: ect temp 75 deg F, throttle plate open 0% MAP pressure 29, Air temp coming into engine is 80 deg F, (so this is summer time start up) pcm will notice that coolant is hot thus engine does not need more gas to run and keep rpms up so it will command pwm to lets say 2.5 ms which means less gas is inserted into the intake.

answer to your question: why hot air on one side and cold on the other side? This has something to do with the duct work. Find duct work diagram and try to visualize what is going in there and use some logic.


Back to loops : notice ECT is very important sensor that is why it is also called "MASTER SWITCH" Pcm first looks up at ect then at everything else and if ect is bad pcm will read ect's signal and then lockup tables will be wrong resulting in wrong injector pulse widths and thus you end up with difficult starts when hot or cold.

[skeeter123]

Hey 3100, are you saying that the engine runs in open loop whenever A/C is on? Even an hour into a 4-hour drive? I'm curious since here in Florida I basically run my cars with A/C on 100% of the time. It's hot and humid. In any parking lot, most cars have big puddles of water/condensation under them. When I first moved here I kept thinking my car had boiled over. What would runnning open-loop forever do to the emission/polution control scheme? Or gas mileage?

[3100]

I think that I have red it somewhere, that ac will trigger open loop. I will dig into it more, but you have a good argument.


but the pollution part that you asked about would be taken care of by hot CAT.


I think that most likely I misread it somewhere.

[3100]

open loop modes:

key on, start up, warm up, hard accelerations and decelerations

I have no idea how did I come up with AC

[alconk]

Mann 3100 thank you! That took some time typing. What is ect? I forgot one other question.. My TCC engages and works fine but as soon as I let off the gas it dis-engages that instant. Back on the gas and it re-engauges. Is this normal? Also on my scanner the first two quad driver's show bad but as soon as it shifts into second gear they both go to good. Hit the brake they go to bad, shifts out of first and back to good. I took it to two shops and nobody can find the problem and said to live with it... The car shifts great and the TCC was checked and showed good??

[3100]

maybe that is just the way your scanner reads it. When it shows that two drivers are bad that could mean that they are unused at that point. If you don't have any codes I wouldn't worry much.

ECT = engine coolant temperature - sensor