Misfire cylinder #4

YukonCO · Jan 6, 2010

I am new to the Kon and Hoe forum and have already gotten some great information. However, I have a problem with my 2000 Yukon (5.3) that I have not figured out. I get a Service engine light only when it idles longer than three minutes. After about 5 minutes it flashes. Stops flashing as soon as I drive it. I get the P0304 error (misfire #4). If i clear it and put a lever on the throttle to keep the idle at 1000 rpm - no error. Here is what I have done so far - changed plugs and wires - changed #4 coil - and changed the inline fuel filter and added B44 injector cleaner. What next before I take to a mechanic? Also, it fires immediately in the morning, but after driven and then shut off - it has to turn over for over 10 seconds before firing up again. Makes no sense to me.

BOSS · Jan 6, 2010

YukonCO said:
I am new to the Kon and Hoe forum and have already gotten some great information. However, I have a problem with my 2000 Yukon (5.3) that I have not figured out. I get a Service engine light only when it idles longer than three minutes. After about 5 minutes it flashes. Stops flashing as soon as I drive it. I get the P0304 error (misfire #4). If i clear it and put a lever on the throttle to keep the idle at 1000 rpm - no error. Here is what I have done so far - changed plugs and wires - changed #4 coil - and changed the inline fuel filter and added B44 injector cleaner. What next before I take to a mechanic? Also, it fires immediately in the morning, but after driven and then shut off - it has to turn over for over 10 seconds before firing up again. Makes no sense to me.

You're not getting a multiple cylinder misfire ??

B

92__silverado · Jan 6, 2010

Not to thread jack but when i start my hoe after sitting all night I get the flashing engine light also. I am hoping it is a plug/wire issue so i will be replacing those this week. If i shut it off and restart not issue.
2003 5.3 with 97k on the clock. Really hoping that its not the intake gasket.

SSmurdered · Jan 6, 2010

i had a misfire on mine a while back. did plugs and wires and coil and didnt fix it. of course the last thing i tried was the fuel injector. no problems since

92__silverado · Jan 6, 2010

Did you clean the Fuel injectors or just replace it. I did a seafoam treatment in the gastank and of course that is when the problem started. But that is when it started getting really cold here too. Hard to tell. Hoping i just fouled the plugs but its odd that it goes away when i restart.

SSmurdered · Jan 6, 2010

my CEL was on all the time and it was when it started to run ****** that i replaced the injector. i didnt try cleaning it first

04Hoe · Jan 6, 2010

Bad Fuel Injector, had the exact problem on my old Impala.

YukonCO · Jan 6, 2010

I have gotten a Random/multiple misfire - but only once - the rest have been misfir cylinder #4

Max · Jan 7, 2010

What brand of wire? Did the issue occur prior to the installation of the new wires or after?

BOSS · Jan 7, 2010

YukonCO said:
I have gotten a Random/multiple misfire - but only once - the rest have been misfir cylinder #4

Clear your codes, reseat the #4 injector harness. If you did all that as you said above, and are getting multiple misfire it could be clogged cats.

B

Misfire cylinder #4

YukonCO

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BOSS

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92__silverado

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SSmurdered

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92__silverado

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SSmurdered

i know u see me

04Hoe

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YukonCO

TYF Newbie

Max

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BOSS

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