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2003 gmc envoy_sle_xl
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Discussion Starter #1
So the Envoy is begging for me to replace it, but I'm too stubborn because I love it. Last Friday on my drive from VA to PA (300miles) it wasn't running the greatest. Over the weekend the SES came on with a PO172 and PO400 code. I didn't have to go anywhere so I wasn't too worried. Monday comes around and I have to drive back to VA, I figured i would get it looked at once I got there, I drove for an hour and the Voy was running horrible. It was all bogged down, reving wierd, wouldn't shift right, so I turned around and brought it back.

The garage just called me and said that the problem was because the throttle body assembly was worn out and that's why it was running bad. It's $427 to get a part next day from GM and installed. Does this sound right? A malfunctioning throttle body will make it run bad and throw those codes? I have 155kmiles these days.

Thanks!
 

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2005 chevy trailblazer_ls
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1,733 Posts
:no:I'd get another mechanic to look at it! I have never seen anyone since I've been here having to replace their throttlebody, just take it off and clean it is the norm!:grouphug:
 

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2003 gmc envoy_sle_xl
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68 Posts
Discussion Starter #3
I can just clean it myself (I did so about 30k miles ago) would a dirty throttle body cause it to run rich?
 

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2005 chevy
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6,469 Posts
If your TB is gunked up enough in the right place, it would cause your throttle plate to stick and either not enough enough air, or too much, for what you need at that particular throttle position. I'd think that could cause a code for running too rich. I think the recommended cleaning interval was about 30K from what I saw on some other threads. Hopefully that's all it is in your case. Good luck.
 

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2002 olds bravada
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2,369 Posts
P0400 is a code for EGR, which our engines don't have. Clean the throttle body and pull the battery cable off while you're at it. If that doesn't help it, look into changing an o2 sensor.
 

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2003 gmc envoy_sle_xl
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68 Posts
Discussion Starter #6
oops...PO440 (I think it was a evap small leak), I cleaned the throttle body and it still runs bad...the O2 sensor isn't that old. My scan tool shows they're both working fine. I tried to rev it up and record to see if it was opening fully or not but the video is bad. I think I'll see if someone can rev it so I can see if it opens.
 

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2003 gmc envoy_slt_xl
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325 Posts
Did you do anything with the air filter ... check, replace, put in a K&N, or recondition your air filter ...???
 

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2003 gmc envoy_sle_xl
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68 Posts
Discussion Starter #8
Last weekend I put in a new air filter, and changed the oil. The fuel filter was replaced about a month ago when I put in a new fuel pump. My scan tool has the TPS%...I'm not sure if that is for the throttle body or what but it seems to start running bad once it gets to 30%. I ordered a new one it will be here Monday, I'll put it on Wed and see if it works.
 

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2003 gmc envoy_sle_xl
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Discussion Starter #10
The same setup that comes with it...has a new fram filter, which is not the problem.
 

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2003 gmc envoy_slt_xl
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No ... but sometimes with the K&N you can get a little downstream oil from the filter which sticks to the MAF sensor and causes some problems ... happened to my nephew when he put his in (although he had a filthy throttle body too, but cleaning the throttle body didn't completely eliminate his problem).

Let us know how the new throttle body works out for you ...
 

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2003 gmc envoy_sle_xl
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Discussion Starter #14
well it wasn't the throttle body assembly...looks like I'll be dropping it off at a GM dealer Tuesday for an expensive investigation!
 

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2003 chevy trailblazer_lt_ext
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213 Posts
po172 code

I had that code come up the other day.The engine was running good except for a fast idle (900) sometimes when at a stop light .I have since cleaned the TB and of course the code reset because of the battery being disconnected.I took it for a test drive and so far no code.If it returns I will be very interested in seeing how you fix your TB so please tell us how you make out.Good luck.:thx
 

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2003 chevy trailblazer_lt_ext
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I just noticed the date of your thread.My bad.I guess you have an answer please let me know how you fixed it. :thx
 

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2003 gmc envoy_sle_xl
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Discussion Starter #17
Sorry for the delay in the reply...

I haven't completely fixed it but I have improved the situation. I decided to unbolt my cat and completely ream it out, it was not the easiest thing in the world to do, but it did the job for now. This immediately was an improvement, the code was gone, it had lots of power and ran great. I still had the PO440 code, but no 172. About a month later I was driving across VA and had a misfire on #6, I replaced that coil no more misfire. Over the weekend (1/1/11) I replaced the rear brakes and noticed that the fuel tank is leaking from around the fill tube. I think this is a common problem on tanks from that year and most likely happened when I replaced the fuel pump. I'm sure this will be another fun weekend project!

Since all of my problems started when I replaced the fuel pump to me it would make sense that the leak from the fill tube caused the engine to run rich which clogged the cat...but I could be wrong!

So I'm not quite sure if I "fixed" it but it sure is running like there is no problem.
 

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2003 chevy trailblazer_lt_ext
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Po172 code

TB cleaning solved my Po172 code.No more fast idle either:woohoo:I had to have my fuel tank replaced because of split seam on the fill pipe.It was under the GM warranty (1500 dollars)thankfully it went while it was still covered.As you may have guessed that was awhile ago.It triggered the same code as if you left the gas cap loose.I guess these tanks are made from plastic and sometimes that tube will split.Another common problem is the sending unit rusting out,but GM will cover that for ten years (extended warranty).It is more likely to happen if your in the snow belt,because of salt.Steel fuel tanks usually rust out after ten years in the salt ,I had hoped a plastic tank would solve that problem,I guess not. :bonk::bonk ::bonk: I hope that your truck is OK now jrk247.
 

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2003 gmc envoy_sle
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Sorry for the delay in the reply...

I haven't completely fixed it but I have improved the situation. I decided to unbolt my cat and completely ream it out, it was not the easiest thing in the world to do, but it did the job for now. This immediately was an improvement, the code was gone, it had lots of power and ran great. I still had the PO440 code, but no 172. About a month later I was driving across VA and had a misfire on #6, I replaced that coil no more misfire. Over the weekend (1/1/11) I replaced the rear brakes and noticed that the fuel tank is leaking from around the fill tube. I think this is a common problem on tanks from that year and most likely happened when I replaced the fuel pump. I'm sure this will be another fun weekend project!

Since all of my problems started when I replaced the fuel pump to me it would make sense that the leak from the fill tube caused the engine to run rich which clogged the cat...but I could be wrong!

So I'm not quite sure if I "fixed" it but it sure is running like there is no problem.
I may be wrong but I thought there was a recall on the tanks. It could have been my Saturn not sure.
 

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2004 chevy trailblazer_ls
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204 Posts
fuel tank woes

I may be wrong but I thought there was a recall on the tanks. It could have been my Saturn not sure.
No recall, but GM finally "extended the warranty" on TBs operated in salt-belt (northeastern) states. Gunk/salt collect on top of the fuel sending unit and corrode the lines, causing fuel and evap leaks. Read this:



Report Date : November 16, 2010 at 08:38 PM
NHTSA Action Number : EA07009





NHTSA Action Number : EA07009 NHTSA Recall Campaign Number : N/A
Make / Models : Model/Build Years:
BUICK / RAINIER 2004
CHEVROLET / TRAILBLAZER 2002-2004
CHEVROLET / TRAILBLAZER 360 2002-2004
CHEVROLET / TRAILBLAZER EXT 2002-2004
CHEVROLET / TRAILBLAZER EXT 370 2002-2004
GMC / ENVOY 2002-2004
GMC / ENVOY 360 2002-2004
GMC / ENVOY XL 2002-2004
GMC / ENVOY XL 370 2002-2004
ISUZU / ASCENDER 2002-2004
OLDSMOBILE / BRAVADA 2002-2004
Manufacturer : GENERAL MOTORS CORP.
Component :
FUEL SYSTEM, GASOLINE:DELIVERY:FUEL PUMP
Date Investigation Opened : July 10, 2007
Date Investigation Closed : August 28, 2008
Summary:
DURING THE COURSE OF THIS EA INVESTIGATION, ODI OBSERVED THAT THE MAJORITY OF THE COMPLAINTS (88%) AND WARRANTY CLAIMS (94%) WERE REPORTED FOR VEHICLES THAT ARE REGISTERED FOR USE IN THE "SALT BELT" REGION OF THE US. THIS AREA INCLUDES 20 STATES IN THE NORTHEAST, MID ATLANTIC AND THE MIDWEST REGIONS AND THE DISTRICT OF COLUMBIA. CONSUMERS IN THE SALT BELT REGION REPORTED TO ODI THAT THEY COULD SMELL FUEL VAPORS IN THEIR VEHICLES WHILE DRIVING. UPON FURTHER EXAMINATION OF THEIR VEHICLES, THEY DISCOVERED THAT FUEL VAPORS WERE COMING OUT OF THE TOP OF THE FUEL TANK. THIS CONDITION IS CAUSED BY CORROSION OF THE RETURN AND SENDER LINES OF THE FUEL PUMP MODULE. WATER AND ROAD SALT COLLECT ON TOP OF THE FUEL PUMP LEADING TO SMALL PINHOLES APPEARING ON THE FUEL LINES. FUEL MAY LEAK AND COLLECT ON TOP OF THE MODULE AND/OR SPILL ONTO THE GROUND. THE DATA EVALUATED UNDER THIS INVESTIGATION REFLECT A RELATIVELY LOW FREQUENCY OF OCCURRENCE THAT LARGELY ARISES IN SALT BELT STATES. GM HAS EXTENDED THE WARRANTY ON THE SUBJECT COMPONENT TO TEN YEARS OR 120,000 MILES. FURTHER USE OF AGENCY RESOURCES DOES NOT APPEAR TO BE WARRANTED AT THIS TIME; ACCORDINGLY, THIS INVESTIGATION IS CLOSED. THE CLOSING OF THIS INVESTIGATION DOES NOT CONSTITUTE A FINDING BY NHTSA THAT NO SAFETY-RELATED DEFECT EXISTS. THE AGENCY RESERVES THE RIGHT TO TAKE FURTHER ACTION IF WARRANTED BY THE CIRCUMSTANCES. FOR ADDITIONAL INFORMATION SELECT DOCUMENT SEARCH.
 
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