throttle body problem
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CF Beginner
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throttle body problem
i have a 08 impala well yesterday i cleaned up the throttle body and after putting back all air intake i took my car for a ride and i noticed that when i released the gas pedal my car well accelerate by itself and the rpm stayed between 1000 to 1300 Rpm. the Rpm goes down to 600 or 700 rpm seconds later i make a complete stop. i need help!!
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Joined: Mar 2011
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Welcome to the forum.
There's no need to panic.
It sounds like you need to do the Throttle/Idle Learn procedure. Look up the procedure for your vehicle at http://www.etechchemicals.com/pdf/ET...-29-GM-TAC.pdf.
There's no need to panic. It sounds like you need to do the Throttle/Idle Learn procedure. Look up the procedure for your vehicle at http://www.etechchemicals.com/pdf/ET...-29-GM-TAC.pdf.
CF Beginner
Joined: Apr 2011
Posts: 24
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From: Canada
Thanks,
The only thing removed (twice) was the throttle body, second time I made sure oring is good and I do not have vacum leak
Tested with vacum gauge, as far as I can tell, I do not have vacum leak.
As I did the PCV test, plugging the fresh air inlet, using vacume gauge in the oil dipstic (dipstic removed) vacmum slowly builds in the crancase, book says if I have vacum, PCV system is ok, no vacume or positive pressure, I could have PVC valve pipe problem, vacum leak, or engine part worn out, rings etc, thus havin too much blow by gases.
Intertingly enought, for the test, I plugged the vacume hose to the breake booster and to the PCV valve, plugging either one seems to correct the ide problem, or make it better as the RPM drops much faster after remowing the foot from the gas pedal. I made sure the PCV tube and its orings are good, so I do not know.
I found the procedure, by googling, url is too long to post, will try to copy & paste below, haven't done it yet.
I think the vacum leak is the possibility, I thoght abut it in the first place, but can not seem to find one. My vacum gauge is not great, (dropped too many times), perhaps I will get a new one, so I will check the vacum really good. I am not sure about this procedure, as it says that if not done the car needs to be driven for a while with speeds over 70 km/h and several decelerations, anyway, will do procedure today, when buddy brings car back to me.
Ziggie
8. Once the engine speed has returned to normal, clear DTCs.
The only thing removed (twice) was the throttle body, second time I made sure oring is good and I do not have vacum leak
Tested with vacum gauge, as far as I can tell, I do not have vacum leak.
As I did the PCV test, plugging the fresh air inlet, using vacume gauge in the oil dipstic (dipstic removed) vacmum slowly builds in the crancase, book says if I have vacum, PCV system is ok, no vacume or positive pressure, I could have PVC valve pipe problem, vacum leak, or engine part worn out, rings etc, thus havin too much blow by gases.
Intertingly enought, for the test, I plugged the vacume hose to the breake booster and to the PCV valve, plugging either one seems to correct the ide problem, or make it better as the RPM drops much faster after remowing the foot from the gas pedal. I made sure the PCV tube and its orings are good, so I do not know.
I found the procedure, by googling, url is too long to post, will try to copy & paste below, haven't done it yet.
I think the vacum leak is the possibility, I thoght abut it in the first place, but can not seem to find one. My vacum gauge is not great, (dropped too many times), perhaps I will get a new one, so I will check the vacum really good. I am not sure about this procedure, as it says that if not done the car needs to be driven for a while with speeds over 70 km/h and several decelerations, anyway, will do procedure today, when buddy brings car back to me.
Ziggie
Procedure 4 Throttle/Idle Learn
Description
The engine control module (ECM) learns the idle position of the throttle plate to ensure the correct
idle. Anytime the throttle body is cleaned or replaced, the ECM must learn the new throttle
position. The idle may be unstable or a DTC may set if the throttle position is not learned.
idle. Anytime the throttle body is cleaned or replaced, the ECM must learn the new throttle
position. The idle may be unstable or a DTC may set if the throttle position is not learned.
Conditions for Running the Throttle Learn Procedure
• DTCs P0101, P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0506, and P0507
are not set.
• The engine speed is between 450-4,000 RPM.
• The manifold absolute pressure (MAP) is greater than 5 kPa.
• The mass air flow (MAF) is greater than 2 g/s.
• The ignition 1 voltage is greater than 10 volts.
are not set.
• The engine speed is between 450-4,000 RPM.
• The manifold absolute pressure (MAP) is greater than 5 kPa.
• The mass air flow (MAF) is greater than 2 g/s.
• The ignition 1 voltage is greater than 10 volts.
Throttle Learn
Important: Do NOT perform this procedure if DTCs are set. Refer to Diagnostic Trouble Code
(DTC) List - Vehicle.
1. Start and idle the engine in PARK for 3 minutes.
2. With a scan tool, monitor desired and actual RPM.
3. The ECM will start to learn the new idle cells and Desired RPM should start to decrease.
4. Ignition OFF for 60 seconds.
5. Start and idle the engine in PARK for 3 minutes.
6. After the 3 minute run time the engine should be idling normal.
Important: During the drive cycle the check engine light may come on with idle speed
DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn.
(DTC) List - Vehicle.
1. Start and idle the engine in PARK for 3 minutes.
2. With a scan tool, monitor desired and actual RPM.
3. The ECM will start to learn the new idle cells and Desired RPM should start to decrease.
4. Ignition OFF for 60 seconds.
5. Start and idle the engine in PARK for 3 minutes.
6. After the 3 minute run time the engine should be idling normal.
Important: During the drive cycle the check engine light may come on with idle speed
DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn.
��
If the engine idle speed has not been learned the vehicle will need to be driven at
speeds above 70 km/h (44 mph) with several decelerations and extended idles.
7. After the drive cycle, the engine should be idling normally.
speeds above 70 km/h (44 mph) with several decelerations and extended idles.
7. After the drive cycle, the engine should be idling normally.
��
If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds
and repeat step 6.
and repeat step 6.
8. Once the engine speed has returned to normal, clear DTCs.
CF Beginner
Joined: Apr 2011
Posts: 24
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From: Canada
Car was here, pulled the codes, it had P0507 & P2127.
Did the Idle Learn Procedure anyway, clearing the codes first of course, but I think this is Pedal Position Sensor problem, hence code P2127, Idle was good after the procedure.
When I pulled throttle body for cleaning couple of days ago, I checked Throttle Poistion Sensor, checked good, actually the sensor is clipped with 5 clips to the throttle body ,(but dealer says you have to buy the whole thing), then I could check the motor with my bench power supply and pots with a meter. The Throttle Position sensor, al it is, it is just two potentiometers, one goes up, one goes down as the throttle moves, easily checked with a meter, preferably old analog ohmeeter.
Buddy left, but will come back, so I will pull and chek the Pedal sensor, after all it again is just 2 potentiometers, will see I can find something wrong with that, or maybe we just replace it, it is not that exepensive.
Ziggie
Did the Idle Learn Procedure anyway, clearing the codes first of course, but I think this is Pedal Position Sensor problem, hence code P2127, Idle was good after the procedure.
When I pulled throttle body for cleaning couple of days ago, I checked Throttle Poistion Sensor, checked good, actually the sensor is clipped with 5 clips to the throttle body ,(but dealer says you have to buy the whole thing), then I could check the motor with my bench power supply and pots with a meter. The Throttle Position sensor, al it is, it is just two potentiometers, one goes up, one goes down as the throttle moves, easily checked with a meter, preferably old analog ohmeeter.
Buddy left, but will come back, so I will pull and chek the Pedal sensor, after all it again is just 2 potentiometers, will see I can find something wrong with that, or maybe we just replace it, it is not that exepensive.
Ziggie
CF Beginner
Joined: Apr 2011
Posts: 24
Likes: 0
From: Canada
Just to add, as I did the Idle Learn Procedure, I was checking for codes and monitoring data, MAP was 29 to 30 kPa, (Manifold Absolute or Barometric Preassure, so I think this is ok, this was when Idling, with engine stopped MAP was reporting 93 kPa, which is the atmosferic pressure today I think, we are 750 meters above see level, so I assume I have no vacum leaks.
Ziggie
Ziggie
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Hmm, I guess I lost track of this thread. So, P2127 says there's a short (to ground) or open in the APP sensor #2 circuit. Do a web search for TSB #07-06-04-019. You may be looking at a corroded IP-to-body harness behind the left kick panel.
CF Beginner
Joined: Apr 2011
Posts: 24
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From: Canada
Car was back yesterday, during the day, all messages, including mulfunction indicator disapeared on their own, scan still showed no codes 0000, P0507 & P2127. I was reading TSB 07-06-04-019, looked to IP to body harnes connector as per TSB, no luck. I removed some pannels, instrument cluster or IP I think, looks like this TSB is not for this vehicle.
The only connector I found was right at the back of instrument pannel, that one looked good. Next I tried to trace the wires from Trottle Pedal sensor, they go to the big bundle under the dash, then some of them come out though the fire wall, in the spot about 3" left to the stearing shaft, then in the engine compartment, some wires go through the 2 connectors and to the PCM and some directly to the PCM. The 2 connectors are at the top of the strut well and they were clean and good.
There was no other connctors under the dash or in the engine area, I am thinking this could be PCM connector, I think PCM is in the air intake area, before the filter, did not check that one out yet.
When I put all together all worked well, cleared the codes, (there was no MIL), car run well untill noon today, when messages (reduced engine power), MIL on came back. I think this is intermittent problem, perhaps temperature related, perhaps bad connction somwhere.
So far, all the ground connections I came upon, looked nice clean and tight, found 2 of them under the dash, couple in the engine compartmnet.
So, problem is not fixed yet.
Ziggie
The only connector I found was right at the back of instrument pannel, that one looked good. Next I tried to trace the wires from Trottle Pedal sensor, they go to the big bundle under the dash, then some of them come out though the fire wall, in the spot about 3" left to the stearing shaft, then in the engine compartment, some wires go through the 2 connectors and to the PCM and some directly to the PCM. The 2 connectors are at the top of the strut well and they were clean and good.
There was no other connctors under the dash or in the engine area, I am thinking this could be PCM connector, I think PCM is in the air intake area, before the filter, did not check that one out yet.
When I put all together all worked well, cleared the codes, (there was no MIL), car run well untill noon today, when messages (reduced engine power), MIL on came back. I think this is intermittent problem, perhaps temperature related, perhaps bad connction somwhere.
So far, all the ground connections I came upon, looked nice clean and tight, found 2 of them under the dash, couple in the engine compartmnet.
So, problem is not fixed yet.
Ziggie