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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > Engine Tunes/Mods

Engine Tunes/Mods Performance Engine Tuning/Engine Modifications

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  #1  
Old 05-15-2009, 12:33 PM
andresmontalvom andresmontalvom is offline
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2005 Chevy TrailBlazer LS
Sandstone Metallic 4.2L I6 2WD
Join Date: Mar 2009
Location: Katy, TX
Posts: 18
PO300 code

Hi everyone. First I want to thank all of you for this helpful site; I’ve been saving so much time and money with your help. Two months ago, I got a permanent Check Engine light on, PO300 “Random Misfire” with a poor idle; after reviewed some of your posts, I cleaned my throttle body, change my Bosch Platinum 2+ spark plugs for Autolite (gaped at 0.043” with a manual gauge, no so trustable) and Seafoam the system (and water pump changed), all those jobs were made possible with your help.
After all this process, what I have right now is a smooth idle and no SES lights 50% of the time, because very often my idle comes bad and the SES light comes on (PO300) when I stop on a light (more often when AC is on) ; and after a while, everything comes fine again. Other thing I noted is very low city MPG (I’m getting something between 13 and 15).
Any ideas you may think I have to explore to gat back my TB to normal again?
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  #2  
Old 05-15-2009, 01:01 PM
jackedupcanyon jackedupcanyon is offline
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2007 GMC Canyon
Steel Gray Metallic Other 4X4
Join Date: Mar 2009
Location: North Atlanta, GA
Posts: 159
Have you cleaned your injectors?

http://www.obd-codes.com/p0300
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  #3  
Old 05-15-2009, 01:13 PM
andresmontalvom andresmontalvom is offline
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2005 Chevy TrailBlazer LS
Sandstone Metallic 4.2L I6 2WD
Join Date: Mar 2009
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I add 1/3 seafoam bottle to a half gas tank and 1/3 trow a vaccum hose. Do you think I have to clean the inyector by another way?

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  #4  
Old 05-15-2009, 02:40 PM
WOOLUF1952 WOOLUF1952 is offline
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2003 GMC Envoy SLT
Magnetic Red Metallic 4.2L I6 4X4
Join Date: Jul 2008
Location: Milwaukee, WI
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Welcome When you cleaned the tb did you take it off to clean both sides?
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  #5  
Old 05-15-2009, 03:08 PM
andresmontalvom andresmontalvom is offline
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2005 Chevy TrailBlazer LS
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Yes, I remove my TB and cleaned both sides until they were like new... It was very dirt !! I did that at 73K, right now I have 80K on my Trailblazer.
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  #6  
Old 05-15-2009, 03:17 PM
andresmontalvom andresmontalvom is offline
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2005 Chevy TrailBlazer LS
Sandstone Metallic 4.2L I6 2WD
Join Date: Mar 2009
Location: Katy, TX
Posts: 18
Do you think it could be a vacuum leak? When I remove the vacuum hose from the brake booster to inject the Seafoam , I noted that the fit were you connect that hose is kind of loose (I can rotated it) , is it normal?
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  #7  
Old 05-15-2009, 04:51 PM
jackedupcanyon jackedupcanyon is offline
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2007 GMC Canyon
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Quote:
Originally Posted by andresmontalvom View Post
I add 1/3 seafoam bottle to a half gas tank and 1/3 trow a vaccum hose. Do you think I have to clean the injector by another way?

Nope. I missed the Seafoamed the system line. Maybe a professional cleaning depending on how long it has been since you put cleaner in the tank last?
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  #8  
Old 05-15-2009, 09:57 PM
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CoyoteFireGuy CoyoteFireGuy is offline
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2004 Chevy TrailBlazer LS
Indigo Blue Metallic 4.2L I6 4X4
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Did you change out your coil packs or just the spark plugs? You may be having a coil pack starting to go bad, or need to re-grease the coil packs.
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  #9  
Old 05-15-2009, 11:58 PM
andresmontalvom andresmontalvom is offline
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2005 Chevy TrailBlazer LS
Sandstone Metallic 4.2L I6 2WD
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Location: Katy, TX
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Quote:
Originally Posted by CoyoteFireGuy View Post
Did you change out your coil packs or just the spark plugs? You may be having a coil pack starting to go bad, or need to re-grease the coil packs.
I just changed the spark plugs. I was thinking that if a X coil is starting to go bad, I'll get a PO30X. About the re-grease, would you please explain me the term, because I'm pretty new with it. May be that was my mistake, because when I changed my spark plugs, I cleaned the coil packs for everywhere . Do I have to grease them with something special?

Thank you
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  #10  
Old 05-16-2009, 12:47 AM
WOOLUF1952 WOOLUF1952 is offline
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2003 GMC Envoy SLT
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Putting a dielectric grease inside the part of the coil that goes down over the plug, helps the boot slide on and helps seal out moisture. It also makes it easier to remove the coil next time.
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po300, random misfire, sls light, spark plugs

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