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Random Misfire


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#1 mawint

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Posted 23 January 2013 - 11:22 PM

Today I started up my truck and it ran fine for the first few minutes but then started to get a rough idle and a check engine light. Took it to O'Reilly's to have the code read and got random misfire. Not sure on the exact code though as the screen was all jacked up. So I bought spark plugs and wires as I haven't changed them since I got it and figure it was due. Changed the plugs and wires, ran fine for the first few minutes then started to idle rough again. Seems to run fine when doing anything but idling.

Really sucks though because gas mileage has been really affected. Anyone know what else to try?

I know some are pictures kind of people so I have attached the pictures of the old spark plugs as they looked funny to me.

(Hover over pictures for titles)
Left = Passenger Side, Furthest left plug is the plug closest to the front and go in order.
Right = Driver Side, Furthest right plug is the plug closest to the front and go in order.

Attached Files



#2 06SierraZ71

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Posted 24 January 2013 - 10:25 AM

Your passenger side is definitely running rich based on your pic. There is probably several areas that could cause this issue. I personally would recommend taking to a shop/dealer and have the codes read and give you a good diagnosis. At home ideas would be to check air filter, inspect/clean throttle body, running a bottle of Techron through your tank (repeat as necessary). May also have an O2 sensor going out but again I'd get it looked at prior to ordering/buying any parts.
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#3 mawint

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Posted 24 January 2013 - 10:44 AM

Ya, my intention wasn't to throw parts at it. I only started with plugs and wires because I knew those needed to be changed anyways and was hoping that it would fix it. Good news was though it ran much better at speed and a little bit better at idle but just felt like it was starved. I think I may run it to a different O'Reilly's and see if a O2 sensor is throwing a code based on the TSB I just found, the reason it drew my attention though is it has been -5 here lately with a wind chill of -25. I do park outside.


Bulletin No.: 05-06-04-063

Date: October 12, 2005

TECHNICAL

Subject:
LM7, L59 or L33 Engines with Cold Start Rough or Incorrect Idle, Misfire, Malfunction Indicator Lamp (MIL) or Flashing Requiring 02 Sensor Replacement (Reprogram PCM)
Models:
2004-2005 Cadillac Escalade
2004-2005 [font=inherit !important][font=inherit !important]Chevrolet
[/font] Avalanche, Silverado 1500, Suburban, Tahoe
2005 Chevrolet Silverado Hybrid (HP2)
2004-2005 GMC Sierra 1500, Yukon, Yukon XL
2005 GMC Sierra Hybrid (PH2)
with Vortec 5300 5.3L V-8 Engine (VINs T, Z, B - RPOs LM7, L59, L33)

Condition

Some customers may comment on a Malfunction Indicator Lamp (MIL) On or that the MIL is flashing. An actual engine misfire may or may not be felt along with an incorrect idle speed. Typically this occurs during cold winter months, on cold engine starts. Some vehicles may have been previously serviced for the same condition. Technicians may also find the following DTCs stored with the Tech 2® P0131, P0133, P0134, P0137, P0138, P0140, P0151, P0153, P0154, P0157, P1133, which may be in conjunction with P0171, P0174, P0300 and P1138.

Cause

Water shock occurs when water droplets are present in the exhaust. The water in the exhaust contacts the sensor element inside the H02 sensor, causing the H02 sensor element to crack.

Correction

Upon diagnostic investigation, the technician may find that the H02 sensor requires replacement. In addition to replacing the affected H02 sensor, these vehicles should also be reflashed with the latest PCM calibration. An updated PCM calibration will be available to dealerships as part of TIS 2000 incremental satellite update 11.0 (NAO version 25.010) or greater. Always, make sure your Tech 2 is updated with the latest software version.

Important: If a DTC P0420 or P0430 is stored along with DTC(s) P0300, the catalytic converter diagnostics in Service Information (SI) must be followed to determine if the catalytic converters are operating properly.
Warranty Information[/font]
[font=verdana, geneva, lucida,]

__________________[/font]



Anyone had any experience with this?

Edited by mawint, 24 January 2013 - 11:49 AM.


#4 mawint

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Posted 25 January 2013 - 11:06 PM

Update: Took the truck to O'Reilly's and put the scanner on it again. This time I had a fault code for Bank 2 Sensor 1 and Freeze Frame showed negative numbers for the sensor. Switched out the sensor and she is all good now.

#5 mawint

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Posted 12 February 2013 - 08:32 PM

So blowing the dust off this one. Truck ran great for a few weeks but now I have started to get a stumble at idle like its misfiring again. I haven't gotten any codes this time however and can be sluggish on take off.

My first thought is plugged cat because while the O2 sensor was on the fritz it blew carbon out the tail pipe and had a foul smell. That doesn't explain why it ran good after putting the new O2 in and just now started to run like crap. Also, I changed plugs and wires before changing the O2 sensor and ran it to test. What is the chance that I fouled a new plug with carbon buildup?

Would it also help to have the PCM updated like the TSB says?

Edited by mawint, 12 February 2013 - 08:38 PM.





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