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Discussion Starter #1
I just got a 2004 Trailblazer with the straight 6 and it has some strange issues that I can't seem to figure out. First I got the truck for free so I figured even if I put 500 into getting it going it would be worth keeping. It hasn't been run since 2016 and the PO said he was having intermittent issues with it losing power and getting the reduced engine power light. So before going to pick it up I did a little research and put together a list of things to check. So I've tested the accelerator pedal position sensors, TPS and throttle body operation, 5v reference wires and grounds, wiring harnesses to and from PCM and through the firewall and the fan clutch harness, switched the ignition switch with a known working switch and tested all the continuity of the throttle by wire system. All the resistance values were within spec and the wiring harnesses were all fine. I forget to mention that before testing I ran the codes and came up with P0622 P0222 P2119 P2122 P2128.
When I saw these codes and they pointed to the throttle by wire system I thought my suspicion was correct. Well after testing and finding everything within spec I tried starting again but it still wouldn't start. I ran the codes again and now all the old ones were gone and now I got a map sensor code. I forget the exact code. Well I went to check it again and now I have no codes. So if you have any advice on what to check next please let me know. Thanks
 

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2002 chevy trailblazer_lt
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Start with the basics. You have a crank-no-start issue. Fuel, Spark and so on. I have a feeling you know the drill.
 

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I followed your advice and found the fuel pump feed line inside the tank that goes from the pump to the top of the tank broken and the missing piece inside the tank. The filler neck was broken typical for the year and EXT model. I plastic welded it back on and it is solid now. The PO worked in the middle of nowhere and the roads were always muddy so with the filler neck broken and daily driving through mud the tank had a considerable amount of dirt inside and the pump was buried in mud. The skid plate on the tank was full of dirt and my eyes will never be the same after all that dirt falling into them!! I would have liked to have washed it before I worked on it but there was no water where it was parked. Now that the fuel pump is getting fuel to the outside of the tank I was able to start the truck but it's misfiring now. I found Bosch Double Platinum plugs in it and 4 coils were bad. The #5 plug had mechanical damage but I can't figure out how the damage could have happened. It looks like something grabbed the negative electrode and opened the gap while taking a bite of it. I examined the inside of the cylinder as best as I could and I didn't see any damage but I'm going to get a camera I can stick inside so I can see the valves and cylinder walls better. So once I get the parts and get them installed I'll see if I need to do some more diagnosis.
 

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Maybe a compression test would be a good idea I think, particularly with that physical plug damage. With all the mud in the fuel tank maybe injectors getting clogged?
 

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Discussion Starter #5
TJBaker I was thinking the same thing about the injectors and muddy tank. But the first thing I need to do is get good spark to all 6 cylinders. No matter what I am going to do an injector cleaning. I did disconnect the fuel line at the regulator and flushed the old fuel out of the lines before I tried starting it. The old fuel was horrible even though I had already added 5 gallons of supreme to it. There was about 8 gallons total that came out. So 3 gallons must have been REALLY bad. The issues that I found with the ignition system were 4 bad coils all the plugs were Bosch Double Platinum and weren't gapped properly and 1 of those plugs had mechanical damage. I've been thinking about that damaged plug and I think it got damaged before it was installed. Reason being is the negative electrode wasn't smashed like most end up that get damaged in the cylinder. The negative electrode had been pulled open and a little piece looked like it had been bitten off. If that happened inside the cylinder what could have caught it and pulled the gap open 1/4"? The only other thing that someone mentioned was detonation. I haven't seen very many spark plugs that have been subjected to detonation but the very few I have seen looked different. I looked inside the cylinder through the plug hole and I figured I would see some shiny metal dents or scratches but it looked like all the other cylinders. I'm going to get a little camera and stick it in there and have a really good look. I'll have my parts on Wednesday so we'll see how it goes.
 

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I too had thought the plug damage likely happened outside the engine.

I need to get some of those mirror attachments for my cheap inspection camera.
 

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Discussion Starter #7
Where did you find a cheap inspection camera? I was looking for one that hooks up to the phone.
 

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I have a Ryobi that uses the phone for a screen but it truly sucks. Connects by wifi but I have to turn off the cell data or the app can't find the camera. And both taking images and copying pictures out of the app is cumbersome. I have seen so many good and reasonable ideas for a product fall flat on their face when it comes to production and applications.
 

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Discussion Starter #9
I found one on Craigslist for really cheap but I wasn't sure if it was going to produce the quality of video I would like to see. I'm really interested in looking in the #4 cylinder to see if there is any damage. I don't think there is going to be anything but I would sleep better at night knowing that the cylinder is ok. I really don't think that damage could have happened inside the cylinder I changed the plugs once on my neighbors Isuzu Ascender and I tried to put the plug in with the plug socket and extension but it wouldn't fit and the plug kinda wedged itself in the head and I had to pull a little to get it out. Opened the gap a little so I had to set it again. It seems maybe the same thing happened here.
 
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