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Engine low power

Tiny
RICHARD MANN
  • MEMBER
  • 2003 GMC ENVOY
  • 4.2L
  • V6
  • 4WD
  • AUTOMATIC
  • 239,942 MILES
Driving for hr going up steep grade sudden loss of power 20-30 sec pump gas recovered 1/2 hr later same thing but this time popping and missing 20 sec 45 min later in town loss of power pull to curb neutral could rev no prob. Down to 1/4 tank replaced fuel line filter fill up added fuel cleaner ok for next 300 k then powered down on freeway pulled in filled up made ferry on exit engine light came on for first time code po172
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Monday, August 3rd, 2015 AT 10:36 PM

16 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I have seen the MAF sensor cause this problem but to be sure lets run down this guide

https://www.2carpros.com/articles/engine-has-low-power-output

we should get the codes as well

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down these guides and report back.

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Tuesday, August 4th, 2015 AT 5:58 AM
Tiny
BOOPERIII
  • MEMBER
  • 1 POST
I had this problem my uncle said the MAF would cause this but I got a new one anyway BAM! Fixed it. Cost me $89.00
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Wednesday, December 4th, 2019 AT 4:39 PM
Tiny
JONESPNH
  • MEMBER
  • 3 POSTS
  • 2003 GMC ENVOY
I have a 2003 GMC Envoy that won't go over 3500 rpms. It goes okay on the flat, but won't go up a hill over 20 mph. We've checked the catalytic converter and the fuel pressures and they are all okay. Occassionally, the check engine light will come on and the code it gives says "rich fuel mixture." My mechanic has given up, any suggestions?
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Wednesday, December 4th, 2019 AT 4:39 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Probable causes of an engine running rich are as follows:

1. Excessive fuel pressure can be cause by restricted fuel return line
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system.
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
HOOVERRWH
  • MEMBER
  • 2 POSTS
  • 2003 GMC ENVOY
  • 194,000 MILES
I have a 2003 gmc envoy with the 4.2L 6 cyl automatic and 2 whl drive. I have random misfires and lose of power. I've changed the plugs, fuel filter and checked the fuel pressure as well as had the cat. Converter checked and it was good. 3 weeks ago the trans stopped working and I pulled it out and found the torque converter was bad. I had the mechanis that rebuilt it about 10 months ago go back thru it and make sure the converter was the only thing bad and he said it was and I watshed him do it. I reinstalled it yeaterday and test drove it today and still had the misfires and lose of power and after about30 miles of driving it flared real bad between 3rd and 4th gear. I took it to a retired trans guy and hes going to put it on his trans scanner to see if anything as gone wrong in the trans again. Do you have any idea what could be causing me these problems or do you think its just the trans causing the issues. Please help. This is driving me bonkers!
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
You 'll probably get amisfire code like a p0300 series check fuel pressure an dlook for maf sensor to be out of whack. These are very hard to diagnose, it may be a throttle body problem as well. Or a vacuum leak.
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
HOOVERRWH
  • MEMBER
  • 2 POSTS
Thanks for your response. It won't throw a darn code! I replaced the maf sensor and I have a used throttle body to check that with soon but right now its at the trans guy to see if the converter is going out again. I almost feel like their related. I'm probably crazy. Lol. Thanks again,
Ray
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
AARONSULLENGER
  • MEMBER
  • 1 POST
  • 2002 GMC ENVOY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 83,600 MILES
Nter your question. My 2002 gmc envoy just started sputtering when excelerating and shakes when stoped and the check engine light comes on and off constantly what could this be
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
The "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired.

Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem. With a 1996 or newer and some 95 cars and you have an AutoZone or Advanced auto parts in your area, they will read them for free. Once you have these code numbers, we can be a lot more specific about what your problem may be.
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
DIVAK68
  • MEMBER
  • 2 POSTS
  • 2002 GMC ENVOY
I am stressed, because I don't know why my car is running so hard or sluggish. It'll run, but just drives harder than usual, these days. Just started on coldest day of the season so far. I didn't let it warm up for long and when I went to eccellerate it was very slow, almost got me into a wreck.
HELP. Stressed out big time in D-Town.
:cry:
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Tune up in good shape?Those have Mass Airflow Meters and I have seen them cause some symptoms like you describe. Have the PCM scanned for any codes that might be stored and get back to us
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
DIVAK68
  • MEMBER
  • 2 POSTS
Thank you for the info. Have an awesome day!
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
RTILLERY
  • MEMBER
  • 1 POST
  • 2002 GMC ENVOY
  • 158,000 MILES
Why do I have power loss when I turn on my AC?
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Possible AC compressor fault or engine malfunction. Some is expected but should be barely noticed. Common fault is dirty injectors or worn plugs. Have check engine light?
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
CANDACE SANSING
  • MEMBER
  • 1 POST
  • 2002 GMC ENVOY
  • 4WD
  • AUTOMATIC
  • 140,000 MILES
It has only happened twice. It seems to happen only when I hit speed bumps. After going over one, my car will not turn nor accelerate. No engine lights on or anything. I tried to put it in park then drive and nothing changes. I still cannot turn or go. I have to turn the ignition off to be able to drive normally again.
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Chck battery to body ground, batt to engine etc. And see if any loose grounds. Otherwise it will need to be scanned for codes by a mechanic.
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Wednesday, December 4th, 2019 AT 4:40 PM (Merged)

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