Car Idles high when cold outside but engine is warm
12-21-2005, 01:44 PM
#1
Teching In
Thread Starter
iTrader: (3)
Join Date: Jul 2005
Location: Ashville, NY
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
Car Idles high when cold outside but engine is warm Not sure if this is the right place to post this but I've been noticing in colder weather (40-50 F) that my engine does not want to drop down to idle all the time. Even when the engine comes up to temp it may still take a few seconds. Even when I'm coasting in gear (6sp) I notice I don't get any compression braking for a few seconds when I let off the throttle. It will typically idle at 1100 rpm for a few seconds and then drop to 800 rpm.
I recently removed my AIR system and pump and I do have a SES light for this, but I wouldn't think it would have an impact, but maybe it does...? For what it's worth, I have a stock cam, but the throttle body is ported (but not too close to the blade). Other than that my car has just intake and exhaust mods (see sig). Can the IAC valve get fouled and get sluggish and stick open? Any experience or suggestions on what causes a warm engine to idle high in cold weather and how to fix it...?
I recently removed my AIR system and pump and I do have a SES light for this, but I wouldn't think it would have an impact, but maybe it does...? For what it's worth, I have a stock cam, but the throttle body is ported (but not too close to the blade). Other than that my car has just intake and exhaust mods (see sig). Can the IAC valve get fouled and get sluggish and stick open? Any experience or suggestions on what causes a warm engine to idle high in cold weather and how to fix it...?
12-21-2005, 01:57 PM
#2
I'm willing to bet it's your throttle body. If the blad has been changed at all or the set screw, or the hole size the idle will be different. If nothing has been changed, I suggest adjusting your set screw down a half turn and see what it does. After your crank the car let it sit and come to idle. Then rev to about 1500 and let it sit for another 15-30 seconds and let it get idle again. Do this about three times. It helps with idle problems.
12-21-2005, 02:01 PM
#4
Here's what I will suggest:
1. Take out the IAC motor, and make sure it is clean. This is cheap and easy to do.
2. Since you removed the AIR system, make sure you plugged up EVERYTHING...especially the **** behind the intake manifold. There are a couple random hoses that need to be plugged that are small and can easily be overlooked. Vacuum leaks suck (literally).
3. If none of that works, it is most likely due to your tune. I had problems with my idle hanging after a ported throttle body, and after educating myself with HPTuners, I figured out that my Base Running Airflow was too high. Your idle trims only work when your car is sitting still in addition to idling (yes, it references your vehicle's speed too). There are long term idle trims, and short term idle trims. Any time your car isn't idling or moving, the STITs go to zero. The LTITs retain their value so it knows where to go when it returns to idle, but it doesn't matter if you are still rolling or you come to a full stop. So if you are coasting to a stop, and your LTITs are telling your IAC to add more air, and it is too much air, it can't correct for it until you come to a complete stop and the STITs come back in action (since they are the only things that can change the LTITs -> LTITs = The average of the STITs).
Make sense?
1. Take out the IAC motor, and make sure it is clean. This is cheap and easy to do.
2. Since you removed the AIR system, make sure you plugged up EVERYTHING...especially the **** behind the intake manifold. There are a couple random hoses that need to be plugged that are small and can easily be overlooked. Vacuum leaks suck (literally).
3. If none of that works, it is most likely due to your tune. I had problems with my idle hanging after a ported throttle body, and after educating myself with HPTuners, I figured out that my Base Running Airflow was too high. Your idle trims only work when your car is sitting still in addition to idling (yes, it references your vehicle's speed too). There are long term idle trims, and short term idle trims. Any time your car isn't idling or moving, the STITs go to zero. The LTITs retain their value so it knows where to go when it returns to idle, but it doesn't matter if you are still rolling or you come to a full stop. So if you are coasting to a stop, and your LTITs are telling your IAC to add more air, and it is too much air, it can't correct for it until you come to a complete stop and the STITs come back in action (since they are the only things that can change the LTITs -> LTITs = The average of the STITs).
Make sense?
12-22-2005, 07:33 AM
#5
Teching In
Thread Starter
iTrader: (3)
Join Date: Jul 2005
Location: Ashville, NY
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MeentSS02
Here's what I will suggest:
1. Take out the IAC motor, and make sure it is clean. This is cheap and easy to do.
2. Since you removed the AIR system, make sure you plugged up EVERYTHING...especially the **** behind the intake manifold. There are a couple random hoses that need to be plugged that are small and can easily be overlooked. Vacuum leaks suck (literally).
3. If none of that works, it is most likely due to your tune. I had problems with my idle hanging after a ported throttle body, and after educating myself with HPTuners, I figured out that my Base Running Airflow was too high. Your idle trims only work when your car is sitting still in addition to idling (yes, it references your vehicle's speed too). There are long term idle trims, and short term idle trims. Any time your car isn't idling or moving, the STITs go to zero. The LTITs retain their value so it knows where to go when it returns to idle, but it doesn't matter if you are still rolling or you come to a full stop. So if you are coasting to a stop, and your LTITs are telling your IAC to add more air, and it is too much air, it can't correct for it until you come to a complete stop and the STITs come back in action (since they are the only things that can change the LTITs -> LTITs = The average of the STITs).
Make sense?
1. Take out the IAC motor, and make sure it is clean. This is cheap and easy to do.
2. Since you removed the AIR system, make sure you plugged up EVERYTHING...especially the **** behind the intake manifold. There are a couple random hoses that need to be plugged that are small and can easily be overlooked. Vacuum leaks suck (literally).
3. If none of that works, it is most likely due to your tune. I had problems with my idle hanging after a ported throttle body, and after educating myself with HPTuners, I figured out that my Base Running Airflow was too high. Your idle trims only work when your car is sitting still in addition to idling (yes, it references your vehicle's speed too). There are long term idle trims, and short term idle trims. Any time your car isn't idling or moving, the STITs go to zero. The LTITs retain their value so it knows where to go when it returns to idle, but it doesn't matter if you are still rolling or you come to a full stop. So if you are coasting to a stop, and your LTITs are telling your IAC to add more air, and it is too much air, it can't correct for it until you come to a complete stop and the STITs come back in action (since they are the only things that can change the LTITs -> LTITs = The average of the STITs).
Make sense?
As for #3, that is exactly what happens / what it does! Now that you gave me some insight to the logic for the PCM to control the idle, the pattern is obvious. I had started to notice that I could only get the car to idle after I let it sit without moving for 5-10 seconds. I thought it was just a strange coincidence - apparently not! I have a RWTD tune, so I'll add this to my list of things to get done on an update I just requested.
Headed to Tampa today for Christmas so I won't mess with it until next week.
Thanks...
12-22-2005, 10:48 PM
#6
Man...if you were closer to me, I'd help you out. I have the HPTuners license for all 2002 and 2001 F-bodies. It really doesn't take long at all to fix it, but if that is what is happening, you'll need to reduce your Base Running Air Flow values a little across the board. If you want to send me a PM to remind me, I'll look at my tune and tell you how much I reduced each value in my table, so you could at least have that as a reference. I have damn near the same intake and exhaust tract as you (TSP 85mm lid, 85mm descreened MAF, Jantzer ported TB, Kooks LTs, no cats, and true duals), so my numbers might get you in the ball park. Let me know...and in the mean time, have a great Christmas!
12-23-2005, 12:14 AM
#7
TECH Fanatic
iTrader: (7)
Join Date: Dec 2003
Location: Las Vegas, from Crystal Lake IL
Posts: 1,305
Likes: 0
Received 0 Likes
on
0 Posts
i cant believe this wasnt mentioned. The cheapest most prone to go out part on the TB which is just a cheap potentiometer. Your TPS, throttle position sensor.
Not much is vacuum driven on the car, if you removed the air you shouuld be fine the air only sends cold air to the cats. I removed mine w/o any issues.
Back to the TPS, mine went out and caused the throttle to be very erratic. I could sit at a stop sign or push in the clutch when i'm rolling at 40mph and the rpm would surge, like a vacuum leak on a carbed car. Also my idle sat between 1100 and 1300. The gm dealer said it was the IAC, I checked it out and it was fine. I bought a new TPS for $30.00 at autozone and the car runs fine now!!
Not much is vacuum driven on the car, if you removed the air you shouuld be fine the air only sends cold air to the cats. I removed mine w/o any issues.
Back to the TPS, mine went out and caused the throttle to be very erratic. I could sit at a stop sign or push in the clutch when i'm rolling at 40mph and the rpm would surge, like a vacuum leak on a carbed car. Also my idle sat between 1100 and 1300. The gm dealer said it was the IAC, I checked it out and it was fine. I bought a new TPS for $30.00 at autozone and the car runs fine now!!
