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Discussion Starter #1 (Edited)
so im working on an 03 tb with the 4.2, and this thing has got me stumped.
very rough idle, stalls, no power, will not accelerate at all. pulled codes, got p1345 along with a random and a cyl3 misfire.

changed plugs, pulled out acdelcos, unknown if they were original or not, but #3 was covered in oil, from the threads to the electrode. replaced with double plat ngks

replaced plugs, cleared codes, tried again.
same thing. misfires like crazy, no power, rough idle, stalls etc.
pulled codes and #3 misfire went away, but random miss and p1345 still there.

next step changed out cam and crank sensors, along with cleaning throttle body, oil change, and an air filter. left battery unhooked after cleaning tb to reset memory, got it all back together again and now NO START. occasionally i will get a puff out of the intake when it stops cranking, but thats it. Random misfire code still there, nothing else.
Any ideas?

EDIT#1 My best guess, and thats all it is at this point, is either fuel pump/filter, or possibly it jumped a tooth on the chain? anyone got odd on one or the other, or something completely different?
 

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2008 gmc envoy_sle
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so im working on an 03 tb with the 4.2, and this thing has got me stumped.
very rough idle, stalls, no power, will not accelerate at all. pulled codes, got p1345 along with a random and a cyl3 misfire.

changed plugs, pulled out acdelcos, unknown if they were original or not, but #3 was covered in oil, from the threads to the electrode. replaced with double plat ngks

replaced plugs, cleared codes, tried again.
same thing. misfires like crazy, no power, rough idle, stalls etc.
pulled codes and #3 misfire went away, but random miss and p1345 still there.

next step changed out cam and crank sensors, along with cleaning throttle body, oil change, and an air filter. left battery unhooked after cleaning tb to reset memory, got it all back together again and now NO START. occasionally i will get a puff out of the intake when it stops cranking, but thats it. Random misfire code still there, nothing else.
Any ideas?

EDIT#1 My best guess, and thats all it is at this point, is either fuel pump/filter, or possibly it jumped a tooth on the chain? anyone got odd on one or the other, or something completely different?
hi, and welcome.

you sure its all back together correct?

you didn't forget to attach a wiring harness? throttle body. coil pack.

best spark plugs for these vehicles is , ac delco 41-103 Iridium
 

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Discussion Starter #3
hi, and welcome.

you sure its all back together correct?

you didn't forget to attach a wiring harness? throttle body. coil pack.

best spark plugs for these vehicles is , ac delco 41-103 Iridium


yeah everythings back together the way it came apart, this isnt my first rodeo lol. i rented a fuel pressure tester to rule out fuel pump/filter, but if not that what else could it be?
 

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Discussion Starter #5
fuel pressure 50psi
190k on the clock.



heres what ive tried so far with part numbers from autozone
spark plugs bosche 8107x6
crank pos sensor su1072
cam pos sensor su1486
oil 7qts 5w30
oil filter s3675xl
air filter sa9345
tb clean
fuel pressure 50psi
fuel filter ff864dl
 

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2005 chevy trailblazer_lt_ext
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A lot to cover. Hmm. The rough idle and stalling would seem to be the throttle body. I would have changed the coil packs when i changed the spark plugs. Also, be careful when plugging the wiring back into the coils, many times the pins can get bent. That's all ive got right now.
 

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Discussion Starter #7
are you saying that i should leave the battery unhooked again to clear the memory after cleaning the throttle body? cause i did that already, with no luck.
at $67 a coil, i wasnt going to just throw 6 at it and hope it helped.
 

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2006 chevy trailblazer_lt_ext
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Wow. When you're done, put down the parts cannon and let's do some real diagnosis using the factory service manual.

P0300 - Random Misfire. I believe if we address this issue, we'll probably solve the P1345 code as well.

Do you have access to a dealer level scan tool or at least a scan tool with the ability to see live data? I'd really love to know what STFT is.

Baring that, inspect the following components:
- the vacuum hoses and seals for splits, restrictions, and improper connections
- the throttle body and intake manifold for vacuum leaks
- the crankcase ventilation system for vacuum leaks
- the PCM ground for corrosion and/or loose connections
- the exhaust system for restrictions
- the fuel for contamination

Reply back and based on your findings, we'll move down the flow chart.
 

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I am dealing with the same type issues, we have put new battery and alternator on it cleaned the tb, vvt, cleaned half of the sensors up from crud, put on a new air filter, checked for cracked hoses, and loose wires since we found dead mice in the engine resealed the manifold I think it's called, and took the pcm off aND checked for bad connection and it looked good. We left battery off for 2/3 days and restarted it and it runs again and still has a bit of chug happening but nothing like it was. But I know he is going to take that cat off underneather cause I am pretty sure it is plugged and not letting enough air go threw it. Wondered if anyone knows if that is a good reason for rough idling. And how do I get the pcm to clean out/relearn itself. I am not in a place to pay the dealer to flash it for me right now at all! Any info would be greatly appreciated thanks ?
 

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2006 chevy trailblazer_lt_ext
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I am dealing with the same type issues, we have put new battery and alternator on it cleaned the tb, vvt, cleaned half of the sensors up from crud, put on a new air filter, checked for cracked hoses, and loose wires since we found dead mice in the engine resealed the manifold I think it's called, and took the pcm off aND checked for bad connection and it looked good. We left battery off for 2/3 days and restarted it and it runs again and still has a bit of chug happening but nothing like it was. But I know he is going to take that cat off underneather cause I am pretty sure it is plugged and not letting enough air go threw it. Wondered if anyone knows if that is a good reason for rough idling. And how do I get the pcm to clean out/relearn itself. I am not in a place to pay the dealer to flash it for me right now at all! Any info would be greatly appreciated thanks ?
Reflashing is not a correct repair unless indicated by service data. Each key cycle of the ignition is a whole new world for the PCM. It doesn't "remember" much once it goes into sleep mode.

Yes a plugged exhaust would cause rough idle, poor acceleration, reduced fuel mileage, a hissing, popping, rattle noises. One way to verify is to observe the B1S1 and B1S2 O2 sensor voltages. You should see the upstream switch back and forth from lean to rich and the downstream to stay fairly constant at any engine speed. Another way is to install a backpressure gauge in the B1S1 O2 hole and compare against service data.
 
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