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2002 gmc envoy_sle
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Discussion Starter #1
I have a 02 Envoy that I just bought. We thought the Timing Chain was out, so tore it down and it's right on. It keep throwing a P1345 code, we even took it to the dealership to have it scanned and it still comes up with the code. Put a new Acuator on, and have done the regular stuff. It runs great, until you put you foot into it, and it falls on its face. No guts at all. Could it be a plugged CAT, doing this? If you slowly build up speed it's better, but it revs high, then if you take your foot off the gas for a second and then put it down, it shifts and the revs come down.
 

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2004 chevy trailblazer_ls
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1st off. Welcome to the site :)

Is it Bogging down. Like going BUUUUUUUU... ?

Might be restriction in the Intake system

Check the throttle body and give it a good clean. maybe a block in the Intake manifold ??Either that or the clutch on the Stator in the TQ converter broke so your not getting any TQ multiplication.

How is it Off the line ?

What actuator did u replace ?
that code if for the Crank or cam position sensor.
 

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Discussion Starter #3 (Edited)
Thank you for your welcome, and your reply.

We replaced the exhaust cam actuator, and the exhaust cam actuator solinoid. It's throwing code P1345, which we know is for the camshaft position, and crankshaft position. However, we have been in and the timing chain is right on the money. Think maybe a plugged CAT, took front 02 sensor out of manifold, have to try in the morning.
 

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2003 chevy trailblazer_ls
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Welcome to the site.
You tore it down thinking it was the timing chain? How long did that take? I think flat rate quotes 8 hrs or something like that.
Put a fitting in the front O2 sensor hole and check the pressure when running. I believe less than 4 PSI is good.
 

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Welcome to the site.
You tore it down thinking it was the timing chain? How long did that take? I think flat rate quotes 8 hrs or something like that.
Put a fitting in the front O2 sensor hole and check the pressure when running. I believe less than 4 PSI is good.
i agree. Ge a pressure tester!

if its not that then all i can think of is the Torque Converter!
 

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Discussion Starter #6 (Edited)
Took it out, without the O2 sensor in, ran a whole lot better. It took awhile to tear it down and put it back together, the book calls for 22 hours, the camshaft runs trough the oil pan. We followed the code, and that's the reason we tore it down, as the previous owner said he had been into it. Now we are thinking the CAT, it may be building too much back pressure, and not let the sensor open up when it should. It needs a new one to pass E-Test anyway. After we do that, if it still has an issue, it may need a new computer, and have that flashed. But your suggestions still may be part of the problem, and is definately worth looking into. We will clear the codes after the CAT and see if it comes back. Thank goodnes there is a mechanic living with us.
 

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non_gmt360 other
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Yep, sounds more like a fuel/airflow issue. The code may be unrelated.
Any black smoke with this happens? Have you checked fuel pressure? Might be worth it to pull the plugs and check color/condition.
 

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2004 chevy trailblazer_lt
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PLEASE don't start throwing more parts (or hours of labour) at this until you spend some time diagnosing possible problems and not symptoms. This forum is a great resource and spend a few hours reading in here before you even think of doing another thing to your truck.

We have told people many times in the past how to diagnose a bad cat, what the symptoms are, what the effects are and the five-minute test that can be preformed - usually for free - to determine positively if the cat is bad.

We have NEVER heard of a bad timing chain on these engines. Never.

On the other hand, we have helped diagnose those codes many times. We don't always hit the right solution right away, but these vehicles, on the whole, are good, solid, dependable and the only problems are relatively predictable throughout the line. This means that if a well-maintained and reasonably-driven vehicle has a problem, someone else probably had that problem too and can help.
 

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Discussion Starter #9
I think your advice Chickenhawk is sound. The only expense we have had with this vehicle is the gaskets and the actuactor solinoid, oil etc. and having the vehicle scanned at the dealership. The labour was free as my boyfriend is a mechanic. This is my son's vehicle and we are trying to get it ready for him. I think that as soon as we figure out the issue with it, it will be a great vehicle for him. I personally love it and would get myself one, I like how it rides, and how it's finished off. I have been doing a lot of reading on this forum, and have found a lot of info already. I will check on how to diagnos the cat issue, but we did pull the O2 sensor and it did run a lot better. Noisy but much more power, and higher revs. The code may still be in the memory, so after we install the CAT (which we need for e-test anyway) it's on the to next step. I am glad I found this forum, the advise and the response has been great.
 

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It's called an exhaust backpressure check, and any good muffler shop can do it for you in 5 minutes. (Look for pressures exceeding 3 or 4 psi.)

It takes a simple compression gauge screwed into the hole that the front O2 sensor goes into. (It's a standard spark plug thread, so most any compression gauge will work.) They make a special exhaust backpressure gauge, and they are useful. A normal compression gauge will work, but they are more designed to be accurate at cylinder pressures around 60 to 120 psi, so it may be hard to read at low psi numbers. An exhaust backpressure gauge is designed to read from 0 to 10 psi, so is much easier to read.

That being said, you seem well on your way to the correct diagnosis anyway. All signs seem to be pointing to a bad cat.

You may also want to try to find out why the cat went bad. They can be destroyed pretty quickly if ever driven with a flashing check engine light (indicating a misfire) but they can also be destroyed over time by undetectable misfires from the wrong brand of spark plugs or constantly running rich due to dirty throttle bodies, bad thermostats or bad coolant temp sensors.

I would always suggest cleaning the throttle body, pulling a plug and seeing what brand it is and look at investing in a good scan tool for him. (Makes a nice gift.)

Good luck and let us know what happens.
 

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Discussion Starter #11
The new CAT is on, took it out for a test drive. It now LIGHTS up, no problem getting the rev's up, and going a buck 20 in no time. The gears are shifting smoothly, the engine light has not come back on. Booking in for an e-test tomorrow. Looking good to go.:thx
 

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Great! Good to hear. (You can now put "solved" into your thread title, by the way.)

You may want to wait a day or two for your emission test. If there were previous codes, it may take time to get them out of history and perform all the required tests. Not saying this is the case with yours, but don't be surprised if they can't test it because there are still a few tests waiting to be run - especially if the battery was disconnected when the cat was replaced.

Also, did you come up with any ideas on what might have caused the cat to fail? Did you pull a spark plug and look at the condition and the brand? How many kilometers on it? Have the plugs and O2 sensor ever been changed, especially if it is over 160,000 KM?

Let us know.
 

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Discussion Starter #13
I will put solved, up as soon I learn how to do it. LOL Anyway, the spark plugs are new NGK, but because we bought the Envoy used we don't know the history. It has about 244K so our guess, poor maintenance in the past. I did call the dealership and let them know. The service advisor said I made his day, he can tell the mechanic that he was wrong about the timing chain. Both O2 sensors look to be recently changed also. It took my boyfriend about 4 hours to do the CAT, the crossmember had to be dropped and the tranny jacked up to get the old one out and the new one in, plus 14 bolts that had to be heated up to get them off. Of course it was wet underneath, with all the ice thawing out. The battery wasn't unhooked during all of this, and the codes have been cleared.

On another good note, I am now looking for an Envoy for myself, I'm thinking of finding one with this issue that someone else can't fix. Now that we know how to do this I could get a great vehicle cheaper.
 

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Change out those plugs.

Your boyfriend will REALLY thank you when you give him that important piece of advice. Just trust us; change them. AC Delco irridium 41-103 plugs.

There is a good chance those plugs are part of why the cat went bad.
 

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Discussion Starter #17
E-Test is done. It passed with great numbers. HCppm 4 & 6, CO% 0.00 on both readings. Thanks a lot for all of your input. I told my boyfriend about changing the plugs, as soon as my son has the money we will get into that.
 

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I have a 02 Envoy that I just bought. We thought the Timing Chain was out, so tore it down and it's right on. It keep throwing a P1345 code, we even took it to the dealership to have it scanned and it still comes up with the code. Put a new Acuator on, and have done the regular stuff. It runs great, until you put you foot into it, and it falls on its face. No guts at all. Could it be a plugged CAT, doing this? If you slowly build up speed it's better, but it revs high, then if you take your foot off the gas for a second and then put it down, it shifts and the revs come down.
 

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I have a 02 Envoy that I just bought. We thought the Timing Chain was out, so tore it down and it's right on. It keep throwing a P1345 code, we even took it to the dealership to have it scanned and it still comes up with the code. Put a new Acuator on, and have done the regular stuff. It runs great, until you put you foot into it, and it falls on its face. No guts at all. Could it be a plugged CAT, doing this? If you slowly build up speed it's better, but it revs high, then if you take your foot off the gas for a second and then put it down, it shifts and the revs come down.
I have the same problem so when I go wide open seems to go to 3000rpms and doesn't really go any faster kinda seems to go slower but if I barely push the gas down I can actually get up too 60+mph but seems to take a bit it almost seems like if you were to max the weight on a car and then pull whatever it is that maxed it out , up a hill just seems to rev if you do find out what this is would u plz let me know I have spent atleast 300+ just in parts in this thing , trying 2 figure out what is going on , so far I have replaced the variable valve timing solenoid twice , crankshaft position sensor 2 , pulled the throttle body and cleaned it still hasn't resolved this issue I have replaced the spark plugs with the iridium plugs , it has 260k+ miles on it plz any help would be greatly appreciated I've been trying to figure this out so my wife and kids bought me a code reader that allows you to read codes and also does everything in real time plz let me know what 2 look for on or to check in real time on my code reader , thank you for everyone that responds
 
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