Idle speed
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Joined: Feb 2012
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Idle speed
I have done the "IDLE RELEARN PROCEEDURE" several times. I cannot get a consistant low speed idle. However with outside temp of 38° to 47° F the idle is perfect at 550 rpm. A4 will sit still with little or no brakes on level ground. The average idle is about 750 rpm at any outside temp above 47° F.
Any suggestions where to look for wear,ect., weak sensor ect. Will be greatly appreciated.
Engine temp above 175° on all tests, does not seem to have much influence on idle. It does get a little better when it reaches 175° but only correct at 38 to 47 outside.
Thanks in advance for any clues or suggestions.
Any suggestions where to look for wear,ect., weak sensor ect. Will be greatly appreciated.
Engine temp above 175° on all tests, does not seem to have much influence on idle. It does get a little better when it reaches 175° but only correct at 38 to 47 outside.
Thanks in advance for any clues or suggestions.
Thread Starter
Advanced
Joined: Feb 2012
Posts: 56
Likes: 2
Idle speed
I have done the "IDLE RELEARN PROCEEDURE" several times. I cannot get a consistant low speed idle. However with outside temp of 38° to 47° F the idle is perfect at 550 rpm. A4 will sit still with little or no brakes on level ground. The average idle is about 750 rpm at any outside temp above 47° F.
Any suggestions where to look for wear,ect., weak sensor ect. Will be greatly appreciated.
Engine temp above 175° on all tests, does not seem to have much influence on idle. It does get a little better when it reaches 175° but only correct at 38 to 47 outside.
Thanks in advance for any clues or suggestions.
Any suggestions where to look for wear,ect., weak sensor ect. Will be greatly appreciated.
Engine temp above 175° on all tests, does not seem to have much influence on idle. It does get a little better when it reaches 175° but only correct at 38 to 47 outside.
Thanks in advance for any clues or suggestions.
Pro
Joined: May 2014
Posts: 670
Likes: 46
From: Indiana
I suspect you've got a small air or vacuum leak somewhere between the MAF and the intake valves. Computer applies idle airflow trims and it likely can't apply enough negative trim at the warmer temperatures.
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Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
A vacuum leak would make it idle HIGHER than stock--not lower----
The most often issues for a lower than stock idle a=on a mostly stock engine is either the T-Body or the MAF--or both----Especially if you have a cold air intake that uses an oiled filter----The oil fouls the MAF and it will read erroneously --The latest technology is now using "oilless" air filters----2ndly your T-body should be cleaned at least once a year--Carbon build up changes the dynamics on it's efficiency---Take the entire air bridge off and open the blade and spray with brake clean or TB cleaner-same goes for the MAF----On the T-Body you will be shocked to see some of the black tar like build up--Cleaning the MAF and T-Body cleans up and restores the idle on 95% of all cars---
The most often issues for a lower than stock idle a=on a mostly stock engine is either the T-Body or the MAF--or both----Especially if you have a cold air intake that uses an oiled filter----The oil fouls the MAF and it will read erroneously --The latest technology is now using "oilless" air filters----2ndly your T-body should be cleaned at least once a year--Carbon build up changes the dynamics on it's efficiency---Take the entire air bridge off and open the blade and spray with brake clean or TB cleaner-same goes for the MAF----On the T-Body you will be shocked to see some of the black tar like build up--Cleaning the MAF and T-Body cleans up and restores the idle on 95% of all cars---
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Thread Starter
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Joined: Feb 2012
Posts: 56
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Idle speed
A vacuum leak would make it idle HIGHER than stock--not lower----
The most often issues for a lower than stock idle a=on a mostly stock engine is either the T-Body or the MAF--or both----Especially if you have a cold air intake that uses an oiled filter----The oil fouls the MAF and it will read erroneously --The latest technology is now using "oilless" air filters----2ndly your T-body should be cleaned at least once a year--Carbon build up changes the dynamics on it's efficiency---Take the entire air bridge off and open the blade and spray with brake clean or TB cleaner-same goes for the MAF----On the T-Body you will be shocked to see some of the black tar like build up--Cleaning the MAF and T-Body cleans up and restores the idle on 95% of all cars---
The most often issues for a lower than stock idle a=on a mostly stock engine is either the T-Body or the MAF--or both----Especially if you have a cold air intake that uses an oiled filter----The oil fouls the MAF and it will read erroneously --The latest technology is now using "oilless" air filters----2ndly your T-body should be cleaned at least once a year--Carbon build up changes the dynamics on it's efficiency---Take the entire air bridge off and open the blade and spray with brake clean or TB cleaner-same goes for the MAF----On the T-Body you will be shocked to see some of the black tar like build up--Cleaning the MAF and T-Body cleans up and restores the idle on 95% of all cars---
Your suggestions are all good, however. I've carefully cleaned the t body and checked and retightened all clamps and connections.
Between 34°f and 47°f the idle is perfect, 500 to 550 in gear, A4. Idle increases with outside air temp to around 750 to 800, just enough to. Be annoying at stop lights and cold traveling down a country road.
Thanks for the interest though. Will keep searching for the answer.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
When the engine is COLD,, it idles off of a SET COLD IDLE TABLE.
After the engine coolant reaches operating temp and the PCM goes into closed loop, the idle is controlled by wide variety of sensors.. O2 sensor, MAF, MAP, ect... The PCM uses all those sensors to adjust idle.
SO,,, You could have a very WIDE variety of sensors that could be contributing to the issue.
??????
WHAT ENGINE.. LS1--LS6
WHAT year car???
How many miles is on the odometer???
When was the last tune up done??
Check the PCV system tubing and hoses for ROT/LEAKS?DAMAGE!!
Here are the TWO PCV Systems that you could have. BOTH are prone to causing big vacuum leaks!!!!!!!!!
LS6 Style:
LS1 Style with the problematic Y fitting t the back of the intake manifold:
After the engine coolant reaches operating temp and the PCM goes into closed loop, the idle is controlled by wide variety of sensors.. O2 sensor, MAF, MAP, ect... The PCM uses all those sensors to adjust idle.
SO,,, You could have a very WIDE variety of sensors that could be contributing to the issue.
??????
WHAT ENGINE.. LS1--LS6
WHAT year car???
How many miles is on the odometer???
When was the last tune up done??
Check the PCV system tubing and hoses for ROT/LEAKS?DAMAGE!!
Here are the TWO PCV Systems that you could have. BOTH are prone to causing big vacuum leaks!!!!!!!!!
LS6 Style:
LS1 Style with the problematic Y fitting t the back of the intake manifold:
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Plug the openings and either pressure test the pluming OR Vacuum test the pluming. Should NOT be any leakage in any of the fittings rubber hoses or plastic tubing!!
Thread Starter
Advanced
Joined: Feb 2012
Posts: 56
Likes: 2
Idle speed
When the engine is COLD,, it idles off of a SET COLD IDLE TABLE.
After the engine coolant reaches operating temp and the PCM goes into closed loop, the idle is controlled by wide variety of sensors.. O2 sensor, MAF, MAP, ect... The PCM uses all those sensors to adjust idle.
SO,,, You could have a very WIDE variety of sensors that could be contributing to the issue.
??????
WHAT ENGINE.. LS1--LS6
WHAT year car???
How many miles is on the odometer???
When was the last tune up done??
Check the PCV system tubing and hoses for ROT/LEAKS?DAMAGE!!
Here are the TWO PCV Systems that you could have. BOTH are prone to causing big vacuum leaks!!!!!!!!!
LS6 Style:
LS1 Style with the problematic Y fitting t the back of the intake manifold:
After the engine coolant reaches operating temp and the PCM goes into closed loop, the idle is controlled by wide variety of sensors.. O2 sensor, MAF, MAP, ect... The PCM uses all those sensors to adjust idle.
SO,,, You could have a very WIDE variety of sensors that could be contributing to the issue.
??????
WHAT ENGINE.. LS1--LS6
WHAT year car???
How many miles is on the odometer???
When was the last tune up done??
Check the PCV system tubing and hoses for ROT/LEAKS?DAMAGE!!
Here are the TWO PCV Systems that you could have. BOTH are prone to causing big vacuum leaks!!!!!!!!!
LS6 Style:
LS1 Style with the problematic Y fitting t the back of the intake manifold:
On cold days 34 to 47°f the idle is very near perfect. Above 48°f the idle is 750 to 800 rpm.
A4 calls for 500 rpm in gear, little or no creap at stop lights. @750 you gotta hold the brake if you don't you're going to hit something or someone.
It's so nice to drive on cold days , I just want it to do the same when the weather warms up. Thanks Bill, you're the best
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I recommend that you find someone with EFI Live or HP Tuners or purchase a scanner that has LIVE SENSOR Monitor capability and data log the sensors.
Something is NOT happy when the outside temp is above a specific deg. The sensor that comes to MIND is the Intake Air Temp Sensor. Its mounted in the AIR BRIDGE on the drivers side. See if it actually reads / matches the outside air temp at engine OFF KEY ON. Then see if it stays fairly close to Outside air temp as the engine warms up.
There NOT expensive. Hell, Just change it if your not willing or able to play.
Also make sure that the connector, wiring and its FEMALE PINS are not spread apart and damaged.
If you monitor the sensor with an OHM METER it should follow temp in a SMOOTH linear increase and decrease with outside temp increase/decrease. Pay particular attention at that TRANSISITION temp where you are having issues.
Bill
Something is NOT happy when the outside temp is above a specific deg. The sensor that comes to MIND is the Intake Air Temp Sensor. Its mounted in the AIR BRIDGE on the drivers side. See if it actually reads / matches the outside air temp at engine OFF KEY ON. Then see if it stays fairly close to Outside air temp as the engine warms up.
There NOT expensive. Hell, Just change it if your not willing or able to play.
Also make sure that the connector, wiring and its FEMALE PINS are not spread apart and damaged. If you monitor the sensor with an OHM METER it should follow temp in a SMOOTH linear increase and decrease with outside temp increase/decrease. Pay particular attention at that TRANSISITION temp where you are having issues.
Bill
Last edited by Bill Curlee; Feb 17, 2016 at 10:11 AM.
Thread Starter
Advanced
Joined: Feb 2012
Posts: 56
Likes: 2
Idle speed
I recommend that you find someone with EFI Live or HP Tuners or purchase a scanner that has LIVE SENSOR Monitor capability and data log the sensors.
Something is NOT happy when the outside temp is above a specific deg. The sensor that comes to MIND is the Intake Air Temp Sensor. Its mounted in the AIR BRIDGE on the drivers side. See if it actually reads / matches the outside air temp at engine OFF KEY ON. Then see if it stays fairly close to Outside air temp as the engine warms up.
There NOT expensive. Hell, Just change it if your not willing or able to play. Also make sure that the connector, wiring and its FEMALE PINS are not spread apart and damaged.
If you monitor the sensor with an OHM METER it should follow temp in a SMOOTH linear increase and decrease with outside temp increase/decrease. Pay particular attention at that TRANSISITION temp where you are having issues.
Bill
Something is NOT happy when the outside temp is above a specific deg. The sensor that comes to MIND is the Intake Air Temp Sensor. Its mounted in the AIR BRIDGE on the drivers side. See if it actually reads / matches the outside air temp at engine OFF KEY ON. Then see if it stays fairly close to Outside air temp as the engine warms up.
There NOT expensive. Hell, Just change it if your not willing or able to play.
Also make sure that the connector, wiring and its FEMALE PINS are not spread apart and damaged. If you monitor the sensor with an OHM METER it should follow temp in a SMOOTH linear increase and decrease with outside temp increase/decrease. Pay particular attention at that TRANSISITION temp where you are having issues.
Bill
This has been my suspect all along but I do not have enough experience with the c5 programming to have a good place to start. You have given me new look at an old problem. I'll get one, repace it and post the results.
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Joined: Feb 2012
Posts: 56
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Idle speed, got the new sensor today and installed it.
I recommend that you find someone with EFI Live or HP Tuners or purchase a scanner that has LIVE SENSOR Monitor capability and data log the sensors.
Something is NOT happy when the outside temp is above a specific deg. The sensor that comes to MIND is the Intake Air Temp Sensor. Its mounted in the AIR BRIDGE on the drivers side. See if it actually reads / matches the outside air temp at engine OFF KEY ON. Then see if it stays fairly close to Outside air temp as the engine warms up.
There NOT expensive. Hell, Just change it if your not willing or able to play. Also make sure that the connector, wiring and its FEMALE PINS are not spread apart and damaged.
If you monitor the sensor with an OHM METER it should follow temp in a SMOOTH linear increase and decrease with outside temp increase/decrease. Pay particular attention at that TRANSISITION temp where you are having issues.
Bill
Something is NOT happy when the outside temp is above a specific deg. The sensor that comes to MIND is the Intake Air Temp Sensor. Its mounted in the AIR BRIDGE on the drivers side. See if it actually reads / matches the outside air temp at engine OFF KEY ON. Then see if it stays fairly close to Outside air temp as the engine warms up.
There NOT expensive. Hell, Just change it if your not willing or able to play.
Also make sure that the connector, wiring and its FEMALE PINS are not spread apart and damaged. If you monitor the sensor with an OHM METER it should follow temp in a SMOOTH linear increase and decrease with outside temp increase/decrease. Pay particular attention at that TRANSISITION temp where you are having issues.
Bill
Engine temp 187 °f
Idle speed 500 rpm in drive , 600 rpm in neutral
Life is good.
This makes 6 issues CF and BC have helped me to resolve.
My sincere thanks and Best Wishes to All contributors.
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New intake temp sensor
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Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
