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2007 gmc envoy_sle
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Discussion Starter #1
Hi everyone. I have an issue hopefully someone from here can help me with. I have a 2007 GMC envoy with a 4.2L6 engine. I'll try to make this short but informative as possible. Over the last 2 months or so my envoy has been losing power little by little. It would be driving great with full power when all of a sudden I would hit a small hill and i can feel it lose power barely making it up the smallest of inclines. Also, it started to idle a little rough dropping in rpm's. So I decided to change the plugs with acdelco iridium's and take the throttle body off and clean it properly. That helped tremendously for a while. Then the same loss of power and idle jumping came back with vengeance. It also started stalling out when I took my foot off the accelerator. (Stopping at a red light). It will always start right back up and go. So I decided to check the fuel pressure and it was good. 55+ at the rail. Checked my coils and cleaned the maf sensor. It seemed to help with the idle issue because it idles great now. It just dont have any power. It kinda feels like it's not able to breath and the longer I drive it the worse it gets. If I really accelerate hard the reduce engine power light comes on and I have no pedal. I have to pull over shut it off, remove the key and wait 3 minutes, starts right back up and goes but with only about 30% of power. I have to baby the fuel pedal or the reduced engine power kicks in and shuts me down. I'm showing 4 codes with the most recent scan p0506,p0101,p0068 and p0411. A mechanic said it could be my throttle body itself so I spent the 300 bucks to get a new one and installed it myself. I did the "relearn" and it idles very smooth at 600rpm, but still no power when accelerating. The trans shifts fine. It starts and cranks fine. The thing I "think" I need to try next is maybe the catalytic converter. I just dont want this thing to nickle and dime me to death. Please help.
 

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Fuel filter? That's been the cause of some similar odd behavior in the past for me (in other vehicles). Particles suspended in dirty fuel get into the filter, build up, and will sometimes seriously restrict fuel flow, especially under acceleration when the pressure forces those particles up against the filter material all at once.
 

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2006 gmc envoy_sle
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Might be the acceleration pedal. The pedal and throttle body are not connected by cable, but speak through computer and sensor. I had reduce engine problems. Changed the throttle body, still reduce engine. Changed acceleration pedal, drives great now.
 

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2007 gmc envoy_sle
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Discussion Starter #4
Fuel filter? That's been the cause of some similar odd behavior in the past for me (in other vehicles). Particles suspended in dirty fuel get into the filter, build up, and will sometimes seriously restrict fuel flow, especially under acceleration when the pressure forces those particles up against the filter material all at once.

I understand what your saying. Fuel filter was my very first thought but I believe my envoy has a non serviceable fuel filter, so I'm not real sure. I know when I tested the fuel pressure I made sure to put it in drive, floor the gas pedal and hold the brake after it was warmed up to operating temp and the pressure never dropped below 55.
 

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2007 gmc envoy_sle
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Discussion Starter #5
Might be the acceleration pedal. The pedal and throttle body are not connected by cable, but speak through computer and sensor. I had reduce engine problems. Changed the throttle body, still reduce engine. Changed acceleration pedal, drives great now.

Is that a sensor mounted on the actual fuel pedal?
 

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2004 gmc envoy_slt
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If you can, get a scan tool on it and capture some live data. Specifically the O2 sensor voltage (downstream and upstream), long term and short term fuel trims. What is the operating temperature (S/B 210 deg. on dash gauge)?
 

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2007 gmc envoy_sle
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Discussion Starter #7
Might be the acceleration pedal. The pedal and throttle body are not connected by cable, but speak through computer and sensor. I had reduce engine problems. Changed the throttle body, still reduce engine. Changed acceleration pedal, drives great now.

Is that a sensor mounted on the actual fuel pedal?
 

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2007 gmc envoy_sle
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Discussion Starter #8
If you can, get a scan tool on it and capture some live data. Specifically the O2 sensor voltage (downstream and upstream), long term and short term fuel trims. What is the operating temperature (S/B 210 deg. on dash gauge)?
It's never been over 220. It fluctuates between 210 and 220
 

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It's never been over 220. It fluctuates between 210 and 220
That temp is WNL... so you're good there.
Get Ye to a bidirectional scanner!

  • Confirm pre- and post-cat oxygen levels.
  • Confirm fuel pressure AND Min/Max flow
  • Confirm TPS values ... especially Tip In.
  • Confirm MAF "sees" actual airflow. (K&N filters mess up a lot of MAFs)
  • Oil pressure as shown on gauge is a "manufactured, not real" value and it MIGHT actually be at the 12-18lb threshold value, tripping reduced power/performance safety settings. (This should also deploy a hammer built into the driver's headrest to maximize adherence to owner/ driver responsibilities). This MIGHT just be a defective oil pressure sensor. If it has oil dripping off the electrical connex, IT'S BAD.
HTH.... it IS, after all.... an internet diagnosis.
 

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2004 GMC Envoy SLT 4.2
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It doesn't even have to be dripping to be bad . I just replaced mine .
No outward sign of leakage , but , it was obvious when I pulled the switch connector .
That's all the oil pressure sensor is , a simple switch . ;)
 

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Yup - just a low threshold, low pressure YES-OR-NO switch that is N/O and closes at around 12 to 18 lbs/in^. It doesn't send true pressure readings - that 'information' is from the GM engineers who put an algorithm into the ECM/PCM to make the gauge read out as if everything was OK under 'normal' operating conditions.

I wasn't too happy when I found this out.

I'm gonna look for a place to tap into the oil pump discharge somewhere - and at least put a real gauge under the hood for --- well, just because!
 

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2004 gmc envoy_slt_xl
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Fuel filter is easily replaced from under the car. Cheap and easy, try that first. Otherwise sound exactly like what I went through with a bad catalytic converter. Changed it and problem gone. Any descent exhaust shop will have an exhaust pressure gauge that screws in place of the front O2 sensor.
 

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2006 Chevrolet Trailblazer LS
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Fuel filter is easily replaced from under the car. Cheap and easy, try that first. Otherwise sound exactly like what I went through with a bad catalytic converter. Changed it and problem gone. Any descent exhaust shop will have an exhaust pressure gauge that screws in place of the front O2 sensor.
2006 and up have no external fuel filter - only the sock in the tank.
 

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2002 gmc envoy_slt
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Is that a sensor mounted on the actual fuel pedal?
Given the codes you pulled, you might want to inspect your fan clutch cabling. They have been known to get frayed and cause a short on the 5V reference signal circuit. The 5V reference signal circuit for the fan clutch is shared with the accelerator pedal (and the throttle body if I am not mistaken) so a short across this line will confuse the ECM and throw it into limp mode.

BTW - The accelerator pedal is drive by wire so there is no cable. When they go bad, you will start to suddenly lose power with no response from the pedal and Engine Reduce Power message because the ECM can no longer determine the position of the pedal. Shutting the ignition off resets it but it will continue to repeat and get worse over time.
 

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2002 Chevy Trailblazer_LS, 2006 Chevy Trailblazer LT
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Hi. Change your variable timing solenoid. It is located right behind the power steering pump/reservoir. You will have to remove the serp belt then loosen the power steering pulley as of what I recall. Picture of the part is attached.
 

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2003 chevy trailblazer_lt_ext
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Hi everyone. I have an issue hopefully someone from here can help me with. I have a 2007 GMC envoy with a 4.2L6 engine. I'll try to make this short but informative as possible. Over the last 2 months or so my envoy has been losing power little by little. It would be driving great with full power when all of a sudden I would hit a small hill and i can feel it lose power barely making it up the smallest of inclines. Also, it started to idle a little rough dropping in rpm's. So I decided to change the plugs with acdelco iridium's and take the throttle body off and clean it properly. That helped tremendously for a while. Then the same loss of power and idle jumping came back with vengeance. It also started stalling out when I took my foot off the accelerator. (Stopping at a red light). It will always start right back up and go. So I decided to check the fuel pressure and it was good. 55+ at the rail. Checked my coils and cleaned the maf sensor. It seemed to help with the idle issue because it idles great now. It just dont have any power. It kinda feels like it's not able to breath and the longer I drive it the worse it gets. If I really accelerate hard the reduce engine power light comes on and I have no pedal. I have to pull over shut it off, remove the key and wait 3 minutes, starts right back up and goes but with only about 30% of power. I have to baby the fuel pedal or the reduced engine power kicks in and shuts me down. I'm showing 4 codes with the most recent scan p0506,p0101,p0068 and p0411. A mechanic said it could be my throttle body itself so I spent the 300 bucks to get a new one and installed it myself. I did the "relearn" and it idles very smooth at 600rpm, but still no power when accelerating. The trans shifts fine. It starts and cranks fine. The thing I "think" I need to try next is maybe the catalytic converter. I just dont want this thing to nickle and dime me to death. Please help.
I had the same problem and took my vehicle into the Chevy dealer. They said that my transmission had to be rebuilt and I had to leave it with them for more than a week to get it done. I drove the car after the "repair" and there was absolutely no difference in performance. I took it back to the dealer and they replaced the catalytic converter and it runs beautifully. No refund on the unneeded trans overhaul even though they misdiagnosed the problem. 🤨
 

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2004 chevy trailblazer_lt_ext
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Hi everyone. I have an issue hopefully someone from here can help me with. I have a 2007 GMC envoy with a 4.2L6 engine. I'll try to make this short but informative as possible. Over the last 2 months or so my envoy has been losing power little by little. It would be driving great with full power when all of a sudden I would hit a small hill and i can feel it lose power barely making it up the smallest of inclines. Also, it started to idle a little rough dropping in rpm's. So I decided to change the plugs with acdelco iridium's and take the throttle body off and clean it properly. That helped tremendously for a while. Then the same loss of power and idle jumping came back with vengeance. It also started stalling out when I took my foot off the accelerator. (Stopping at a red light). It will always start right back up and go. So I decided to check the fuel pressure and it was good. 55+ at the rail. Checked my coils and cleaned the maf sensor. It seemed to help with the idle issue because it idles great now. It just dont have any power. It kinda feels like it's not able to breath and the longer I drive it the worse it gets. If I really accelerate hard the reduce engine power light comes on and I have no pedal. I have to pull over shut it off, remove the key and wait 3 minutes, starts right back up and goes but with only about 30% of power. I have to baby the fuel pedal or the reduced engine power kicks in and shuts me down. I'm showing 4 codes with the most recent scan p0506,p0101,p0068 and p0411. A mechanic said it could be my throttle body itself so I spent the 300 bucks to get a new one and installed it myself. I did the "relearn" and it idles very smooth at 600rpm, but still no power when accelerating. The trans shifts fine. It starts and cranks fine. The thing I "think" I need to try next is maybe the catalytic converter. I just dont want this thing to nickle and dime me to death. Please help.
I have a 2004 that had similar issues, threw a bunch of codes about cam position sensor, o2 sensor, VVT solenoid and I replaced all with limited success. Turned out to be a plugged catalytic converter. Pull the o2 sensor and check for back pressure. Might not be the problem but a fairly easy test to do or have done. I went to my transmission guy and he ruled out the transmission and found and fixed the plugged cat.
 

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I had the same problem and took my vehicle into the Chevy dealer. They said that my transmission had to be rebuilt and I had to leave it with them for more than a week to get it done. I drove the car after the "repair" and there was absolutely no difference in performance. I took it back to the dealer and they replaced the catalytic converter and it runs beautifully. No refund on the unneeded trans overhaul even though they misdiagnosed the problem. 🤨
I'd haul their posteriors to court for fraud. I honestly hate dealerships for many reasons, This is one of the biggest activities that should be investigated. Too bad other states don't have a Bureau Of Automotive Repair to haul these jerks into the fire with fines, Marshal-Keepers and court ordered lock-downs.
I used to investigate them for the BAR in SoCal and the horrible fraud and bait-n-switch tactics was outstanding!
 

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2003 chevy trailblazer_lt_ext
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I have a 2004 that had similar issues, threw a bunch of codes about cam position sensor, o2 sensor, VVT solenoid and I replaced all with limited success. Turned out to be a plugged catalytic converter. Pull the o2 sensor and check for back pressure. Might not be the problem but a fairly easy test to do or have done. I went to my transmission guy and he ruled out the transmission and found and fixed the plugged cat.
I agree with checking out the cat converter first. That is all that mine turned out to be after the dealer had convinced me to rebuild the transmission. Should have taken it to my mechanic rather than a dealership.
 
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