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03 Chevy Silverado Misfire


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#1 timmdogg2

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Posted 14 August 2008 - 11:03 PM

hey, I have a 2003 chevy silverado exd cab 5.3L. I recently changed my spark plugs and now i have misfires. I have been trouble shooting this problem for 3 days and it seems to be getting progressively worse each day. My neighbor has a code checker and it says that i have a random cylinder misfire (code p0300). We checked to see what cylinders were misfiring and in a 5-10 minute span i had over 1200 misfires in cylinder 1, about 500 in cylinder 8, and only 1 or 2 in every other cylinder. My ignition timing is going nuts ranging from 3 to 27 when the truck is just idiling. I have changed sparkplugs, and serpinteen belt prior to this happening. Since the problem has started, i have changed spark plug wires, cleaned my k&n air filter, and changed fuel pressure regulator. I have taken the spark plugs out made sure they were the correct ones and that i did not have any damage to them. Since i have a random mis fire i know that it eliminates any problems that have to do with individual cylinders or parts such as sparkplugs, wires and individual coil packs. It also back fires on acceleration occasionally, i do not have a clogged cat, my fuel pressue is a bit low at idle (50 at idle-62 when steppin on gas). I have also eliminated mass air flow sensor and fuel mixture is good at 14.6 I have used differents types of gas and did not effect it either way. it only seems to really mis under load(in gear) in low rpms, when i am above 2000 rpms u can not really tell anything is wrong, but like i said it is getting worse. somebody told me to change crackshaft sensor and im going to try that tommorrow. does anybody have any ideas? im getting frusterated!
I also have 2 new codes that popped up today, they dont sound like they relate to my problem above but u never know they are u1026 and u1041

Edited by timmdogg2, 14 August 2008 - 11:09 PM.


#2 Griffin86

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Posted 14 August 2008 - 11:09 PM

hey, I have a 2003 chevy silverado exd cab 5.3L. I recently changed my spark plugs and now i have misfires. I have been trouble shooting this problem for 3 days and it seems to be getting progressively worse each day. My neighbor has a code checker and it says that i have a random cylinder misfire (code p0300). We checked to see what cylinders were misfiring and in a 5-10 minute span i had over 1200 misfires in cylinder 1, about 500 in cylinder 8, and only 1 or 2 in every other cylinder. My ignition timing is going nuts ranging from 3 to 27 when the truck is just idiling. I have changed sparkplugs, and serpinteen belt prior to this happening. Since the problem has started, i have changed spark plug wires, cleaned my k&n air filter, and changed fuel pressure regulator. I have taken the spark plugs out made sure they were the correct ones and that i did not have any damage to them. Since i have a random mis fire i know that it eliminates any problems that have to do with individual cylinders or parts such as sparkplugs, wires and individual coil packs. It also back fires on acceleration occasionally, i do not have a clogged cat, my fuel pressue is a bit low at idle (50 at idle-62 when steppin on gas). I have also eliminated mass air flow sensor and fuel mixture is good at 14.6 I have used differents types of gas and did not effect it either way. it only seems to really mis under load(in gear) in low rpms, when i am above 2000 rpms u can not really tell anything is wrong, but like i said it is getting worse. somebody told me to change crackshaft sensor and im going to try that tommorrow. does anybody have any ideas? im getting frusterated!
I also have 2 new codes that popped up today, they dont sound like they relate to my problem above but u never know they are u1026 and u1041


Did you get the spark plug wires on the respective spark plugs?
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1999 Gmc Sierra SLE Z-71 SOLD! :D

1991 Gmc Sierra SLX 4x4 303k km bought for $900. The hunting truck!

2008 Chevy Silverado LTZ Vortec Max - 3 in body lift, 4 inch CST suspension lift, 285/65r20 (35s) BFG all terrains, 20x9 MKW M-26, stainless steel grill, chrome bug deflector, chrome mirrors, chrome gas door, stainless steel box rails, Pace Edwards roll up box cover, husky liner floor cover, stainless steel mud flaps, chrome door handles, Chrome 6" oval nerf bars, 3m Paint Protection.

2004 Polaris RMK 800 - selling it for an 09 Yamaha Nytro

#3 timmdogg2

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Posted 14 August 2008 - 11:19 PM

hey, I have a 2003 chevy silverado exd cab 5.3L. I recently changed my spark plugs and now i have misfires. I have been trouble shooting this problem for 3 days and it seems to be getting progressively worse each day. My neighbor has a code checker and it says that i have a random cylinder misfire (code p0300). We checked to see what cylinders were misfiring and in a 5-10 minute span i had over 1200 misfires in cylinder 1, about 500 in cylinder 8, and only 1 or 2 in every other cylinder. My ignition timing is going nuts ranging from 3 to 27 when the truck is just idiling. I have changed sparkplugs, and serpinteen belt prior to this happening. Since the problem has started, i have changed spark plug wires, cleaned my k&n air filter, and changed fuel pressure regulator. I have taken the spark plugs out made sure they were the correct ones and that i did not have any damage to them. Since i have a random mis fire i know that it eliminates any problems that have to do with individual cylinders or parts such as sparkplugs, wires and individual coil packs. It also back fires on acceleration occasionally, i do not have a clogged cat, my fuel pressue is a bit low at idle (50 at idle-62 when steppin on gas). I have also eliminated mass air flow sensor and fuel mixture is good at 14.6 I have used differents types of gas and did not effect it either way. it only seems to really mis under load(in gear) in low rpms, when i am above 2000 rpms u can not really tell anything is wrong, but like i said it is getting worse. somebody told me to change crackshaft sensor and im going to try that tommorrow. does anybody have any ideas? im getting frusterated!
I also have 2 new codes that popped up today, they dont sound like they relate to my problem above but u never know they are u1026 and u1041


Did you get the spark plug wires on the respective spark plugs?



What do you mean? I got the wires after the misfires had started, thinking that maybe i broke a wire taking the old ones off.

#4 Griffin86

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Posted 14 August 2008 - 11:25 PM

hey, I have a 2003 chevy silverado exd cab 5.3L. I recently changed my spark plugs and now i have misfires. I have been trouble shooting this problem for 3 days and it seems to be getting progressively worse each day. My neighbor has a code checker and it says that i have a random cylinder misfire (code p0300). We checked to see what cylinders were misfiring and in a 5-10 minute span i had over 1200 misfires in cylinder 1, about 500 in cylinder 8, and only 1 or 2 in every other cylinder. My ignition timing is going nuts ranging from 3 to 27 when the truck is just idiling. I have changed sparkplugs, and serpinteen belt prior to this happening. Since the problem has started, i have changed spark plug wires, cleaned my k&n air filter, and changed fuel pressure regulator. I have taken the spark plugs out made sure they were the correct ones and that i did not have any damage to them. Since i have a random mis fire i know that it eliminates any problems that have to do with individual cylinders or parts such as sparkplugs, wires and individual coil packs. It also back fires on acceleration occasionally, i do not have a clogged cat, my fuel pressue is a bit low at idle (50 at idle-62 when steppin on gas). I have also eliminated mass air flow sensor and fuel mixture is good at 14.6 I have used differents types of gas and did not effect it either way. it only seems to really mis under load(in gear) in low rpms, when i am above 2000 rpms u can not really tell anything is wrong, but like i said it is getting worse. somebody told me to change crackshaft sensor and im going to try that tommorrow. does anybody have any ideas? im getting frusterated!
I also have 2 new codes that popped up today, they dont sound like they relate to my problem above but u never know they are u1026 and u1041


Did you get the spark plug wires on the respective spark plugs?



What do you mean? I got the wires after the misfires had started, thinking that maybe i broke a wire taking the old ones off.


I misread my bad. My buddy had the same problem. It was his 02 sensors.
Posted Image
1999 Gmc Sierra SLE Z-71 SOLD! :D

1991 Gmc Sierra SLX 4x4 303k km bought for $900. The hunting truck!

2008 Chevy Silverado LTZ Vortec Max - 3 in body lift, 4 inch CST suspension lift, 285/65r20 (35s) BFG all terrains, 20x9 MKW M-26, stainless steel grill, chrome bug deflector, chrome mirrors, chrome gas door, stainless steel box rails, Pace Edwards roll up box cover, husky liner floor cover, stainless steel mud flaps, chrome door handles, Chrome 6" oval nerf bars, 3m Paint Protection.

2004 Polaris RMK 800 - selling it for an 09 Yamaha Nytro

#5 timmdogg2

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Posted 14 August 2008 - 11:31 PM

i thought that too, but i checked and that was not the problem. Plus that would have came up in the code check. Dont know if this symptom pertains to the problem either but i also had trouble starting my truck 3 or 4 times in the last week . i put the key in and turn forward everything shutoffs as it is supposed too but the starter does not even make a sound not even a click, and then 2 minutes later it will start when i try it again

#6 mbowman

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Posted 15 August 2008 - 11:09 AM

From what you said it could either be your battery or the battery wiring. You said that you tried to start and everything went dead, sounds like battery to me.

Also when you are idling the alternator is not putting out that much, but when the revs increase it will start to generate 14V ish, which is enough to run the truck.

Check your battery, better yet have autoparts store load test. Check for corrosion on the posts and damage to the cables.

Martin

#7 mi.bowtie

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Posted 15 August 2008 - 08:15 PM

Tim. are you sure it is not a BAD CAT. Are all the majority of misfires on the same side?
2003/2004 are notorious for bad Cats. 5.3

#8 wdavrac

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Posted 11 December 2008 - 10:06 PM

Hello, all was this issue ever resolved my 05 5.3l is acting exactly the same.... frustrated please pm me thanks




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