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2003 chevy trailblazer_ls
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Discussion Starter #1
Although my '03 TB 4.2L (3.73 rear) has been running a lot better after a host of modest improvements, it still lacks the "oomph" of my '02 Bravada (also a 3.73 rear) clone car. I'm going on 121k miles now and I had a couple of folks on this forum who suggested the catalytic converter maybe plugged, but I mentally ruled it out because it's a 2003 model year and that seemed like a premature failure. Now I'm probably seeking a second opinion.

I had ran with a stuck open thermostat, for probably god knows how long, operating around 160 degrees according to the gauge. The problem is, I drove it around that way assuming it appeared normal because there never was a SES light. So running "too rich" for a long time could have screwed up the cat, right?

There still isn't an SES light. No cat code or 02 sensor code. Nothing. As a sidebar, here are some driveability symptoms. It still feels sluggish. For example, when you take off doing a hard launch from a standstill with the shifter in D, the engine will max rev 4000 rpm (no higher than that) in 1st gear, bogs (feels like it runs out of breath as a slight pause for a second), and then upshift into 2nd gear. If I put the shifter in L and manually shift the tranny to engage 2nd, the engine will rev out to 5000 rpm while in L (don't know if I should let it rev higher just for the hell of it but I don't want to break anything neither).

So without the SES light coming on, is it possible for the cat to be plugged?
 

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2005 chevy trailblazer_ls_ext
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I mentally ruled it out because it's a 2003 model year and that seemed like a premature failure. Now I'm probably seeking a second opinion.
I don't know what you are looking for here. Are you looking for an answer you like better? We gave you our opinion already and you admit you "ruled it out". On these vehicles, "premature failure" is sometimes fairly normal.

Use the search function and see how many people over the last 2 or 3 years have replaced converters, especially on 02 and 03 models.

You also admit it ran rich for an extended period of time. That is rather hard on converters. Many people have driven a long time with a bad cat and with poor performance and never get a SES light.

Based on what you said about your tranny shifting, maybe you have a transmission or PCM problem. Might be time to let a professional do some testing.
 

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2003 chevy trailblazer_ls
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Discussion Starter #3
I have decided to take the advice and declare a "bad cat." Now the fun part. Which catalytic converter brand should I purchase as a replacement that is as equal or maybe better than the OEM? Actually, who makes the OEM cat? Hopefully not some China or Taiwan Autozone special lol.
 

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2005 chevy trailblazer_ls_ext
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Personally I would take the old cat off FIRST, and see if that helps your problems. You could live with the noise for a short time, or buy a pipe to temporarily replace the cat.

As far as what brand of cat, sorry but I have no clue as to who makes the OEM. Fortunately I haven't had to replace mine yet. Note I said "yet"! :hopeless
 

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2003 chevy trailblazer_lt_ext
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Trailblazer cat converter

My experience with the cat converter on an 03 TB EXT is as follows:

I was driving on the hwy at approx. 120 km/hr when I felt a jolt and the engine seemed to have lost power; I would step on it, the engine would rev high but the truck would not go above 80 km/hr.
I thought that I had lost a gear, so I took the truck into a transmission shop for a test drive and the tech confirmed that the tranny was ok; he suggested that I had an issue with the engine.
I went home and changed the spark plugs, checked the around the engine for anything unusual and could not find a thing.
I then concluded (after reading some info on the Internet) that the cat converter could be faulty; took the cat converter out and had it replaced (by a mechanic, as I don't have a welding machine and I found it impossible to remove the darn thing from the underside of the car); truck runs normal now.
I have never had any warning lights on during this process.
Hope this helps.
 

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2002 chevy trailblazer_ltz
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Hmmmm, Stuck open therm. kinda sounds like your on the right track....:undecided Whats the call on dealer replacment for free? Didn't I read that somewhere???? :m2:
 

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2003 chevy trailblazer_lt_ext
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Sorry, I do not remember which cat I bought; I bought it from Rockauto.com and it was one of the cheaper ones (less than $300 if I recall).

As far as shifting, the tranny seems to act ok, after 200,000 km it had to put up with.

To answer to the previous comment (by guano2), my experience with the dealers was not so good so I gave up a long time ago and started fixing my car on my own. As mentioned above, the truck has 200k on it; it is 7 years old, so I believe all the warranties are gone; I never purchased an extended warranty.

Knock on wood, the truck is running ok and still starting in -35 degrees C after being all night out (unplugged).
 

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2002 gmc envoy_slt_xl
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I'll add my experience here.

I was having the same symptoms as the OP with my 2002 Envoy XL SLT. From reading Trailvoy, I was pretty sure it was also my catalytic converter. It was really starting to have major problems with taking off from stops and I've even gotten a better idea of what streets in my city has the biggest hills as my power would really bog down if I had to make it up an incline. For several weeks there I was driving in the slow lane.

I was able to find the catalytic converter on Amazon for $200... with free shipping. For the XLs make sure you get the CC assembly for the longer wheelbase, btw. Another $120 in labor charges with the local shop close to my neighborhood and my GMC Envoy now runs like a champ again.

Hopefully this helps somebody. I know I've gotten a LOT from this site in the short time that I've owned my Envoy, so hopefully I'm giving back a bit here.

Love the site!!!
 

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2006 chevy trailblazer_ss_lt
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a plugged cat is easily diagnosed. unscrew the upstream o2 sensor from the exhaust manifold and go for a short drive. if the power returns, then get a new catalytic converter. and fix whatever caused it to clog in the first place (stuck open tstat probably)
 

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2005 chevy trailblazer_lt_ext
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I have a 04' TB EXT 4.2, I started losing power when the engine got over 210 degrees. I thought it had something to do with the fan clutch so I replaced it. The fan clutch did not help. Then I got two P codes, P0172 and P0132. Both codes deal with rich condition at the upstream O2 sensor. I replaced the upstream O2 sensor, truck still had no b*lls. I looked at this post and started thinking maybe it's the cat. I called a muffler shop and asked how much a new cat would cost, they quoted $230 plus tax. The problem was they where closed for the day. :( The guy told me to drill holes in the exhaust before and after cat, he could always weld them back up. I drilled the holes and found it was the cat. I never heard of doing this before, what a great way to figure out if you have a plugged cat!:)
 

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2005 chevy trailblazer_ls_ext
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Sluggish issues / out run by a mazda protge 4 dr

:cry:Hey Guys I'm new the trailbalzer world.
I have a 05 ext 4x4 lt with a 4.2 vortec it have about 112000 miles.

ITS a SLUG

it has terrible acceleration I got jumped and out run by a mazda protge 4 dr today.

I was told maybe the plugs so I changed them and the air filter.

in park with the pedal to the floor it only revs 3000 going down the road it sound like the motor is killing itself just to run 60 mph

if I stand on it it revs to 5000 and kinda stays there then shifts but i'm not really accelerating much.

In reading the post it sounds like my converter is stopped up??????
 

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2004 gmc
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26,181 Posts
Yes, and you should troubleshoot it to be sure before changing it.

3000 RPM limited in PARK and NEUTRAL is a programming restriction in the PCM, to reduce the amount of abuse that children could otherwise do to the tranny if they revved it up and dropped the shifter into drive. GM wanted to reduce their warranty cost.
 

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2005 chevy trailblazer_ls_ext
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converter plugged

:)hey thanks for the input guys

I un hooked the exhaust and it burns rubber on pavement (power braking of course)

so tommorrow the cat comes off pipe goes in and magna flow 16833 dual exhaust

next week a cold air induction and super tune from Blanchard's Performance
 

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2003 chevy trailblazer_ls
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11 Posts
new catalytic converter

I got a tbls 2003 with 81 miles,early there was no pressure in engine,the rpm get to 600 when parking!!i replaced the catalytic converter with new one and it got back to 800,every thing normal.:yes:
 

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2003 chevy trailblazer_ls
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:cry:Hey Guys I'm new the trailbalzer world.
I have a 05 ext 4x4 lt with a 4.2 vortec it have about 112000 miles.

ITS a SLUG

it has terrible acceleration I got jumped and out run by a mazda protge 4 dr today.

I was told maybe the plugs so I changed them and the air filter.

in park with the pedal to the floor it only revs 3000 going down the road it sound like the motor is killing itself just to run 60 mph

if I stand on it it revs to 5000 and kinda stays there then shifts but i'm not really accelerating much.

In reading the post it sounds like my converter is stopped up??????


easy,got to muffler shop,and tell him to remove the muffler the is under the engine,or clean it,because it's plugged,don't wait,this problem could hurt your engine bad!
 

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2005 chevy trailblazer_lt_ext
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Changed the cat this weekend. I had my wife drive it and she said much better. Going to look into putting a flowmaster on it next.
 

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2003 chevy trailblazer_lt
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The cat on my Trailblazer was clogged

We purchased a new 18' travel trailer and couldn't tow it above 50 mph. The engine revved and the trans went to 4,000 rpm before shifting. The dealer said the cat was clogged (87,000 miles) and wanted $950 to replace. I called GM Corp. The factory warrenty was to 80,000 miles. The girl at GM called the service department and they agreed to replace the cat for the cost of the cat alone, $250. The most important thing is that the thermostat was open for a few months before and the engine wasn't coming up to temp. The ECM would not go into closed loop until the temp is right. The engine ran rich and clogged the cat. If your stat is defective and you get the underheat code have the stat replaced immediately.
 

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2003 chevy trailblazer_lt
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plugged cat

hey whats happinin,


you defenatly have a plugged cat. my 03 went at 70,xxx. i replaced it all with a highflow magnaflow metallic spun cat and magnaflow straight thru muffler. what a difference in power,sound,performance, and mpgs. highly recomend it. please contact me if u have any questions about this. i can tell you whatever you need to know. that is deffenatly your problem.


brian
 
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