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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevrolet Tahoe 4x4: I have a 2003 Tahoe with a 5.3 flex fuel

Customer Question

I have a 2003 Tahoe with a 5.3 flex fuel engine. For 2.5 years now it INTERMITTENTLY idles and runs rough up to about 1500 rpm, and throws a p0300 code. I've done the usual and expected; changed all plugs and wires, and it has a new OEM fuel pump (separate issue). The only thing that made even the slightest difference was replacing the fuel pressure regulator. But that has merely reduced the frequency and magnitude of the problem. It can go a month or more without an issue and then out of the blue it will idle rough and buck up to 1500 rpm or so. A few miles after that starts, the engine light will either come on steady or begin flashing and eventually stay on. This may last 2-5 days give or take, and then all of a sudden as mysteriously as it came on, it will disappear, until the next time. Again, the key word here is INTERMITTENTLY. I presume the terms "RANDOM MISFIRE" and "INTERMITTENT" would rule out the possibility of things like plugs, wires, coils, fuel pump (new OEM), vacuum leaks, CAT converter, sensors, etc.???
Any thoughts or suggestions?
Pleeeeaaassseee Heeeeelllllllpppp!!!!!
Thanks in advance.
Submitted: 2 years ago.
Category: Chevy
Expert:  Gary replied 2 years ago.
Welcome! My name is ***** ***** I will do my best to assist you with this problem.Ask me about added features such as phone contact anytime if you wish !
I am sorry for the long wait
when the P0300 code is set can you get access to a scan tool to view history and current misfires and see in the history misfire data which cylinders incremented misfires ?
knowing if its all 8 cylinders or just a few cylinders will cut this problem in 1/2 knowing if its related to all the cylinders or just 1 or 2 cylinders
Customer: replied 2 years ago.
P0300 code means it is a RANDOM misfire condition and is not consistently related to any specific cylinder or cylinders, hence the mystery of it all. Sorry pal but I'm neither pleased nor impressed with your response as I've been aware of what you just told me for the past 2.5 years!
Expert:  Gary replied 2 years ago.
no need to be rude pal
I am trying to help you
i am just asking questions so we can get to the bottom of this issue
as we do not want to guess
yes random misfire we know that but WHICH cylinders are in fact misfiring
it will save which cylinders misfired in the data list under history misfires
i am not really impressed with your follow up with my question i asked
no one has been able to find this problem because no one is diagnosing this correctly and assuming when we need to know right off the bat which cylinders are showing a misfire
it makes a big difference if its one or two cylinders or ALL 8 misfiring when it triggers the P300 code
its a wonder why this is not fixed yet with the assuming and guessing going on