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Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 28319
Experience:  14 years GM dealer Technician.
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I have a 2007 suburban ltz flex fuel. I'm getting a

Customer Question

I have a 2007 suburban ltz flex fuel. I'm getting a p0300 random misfire
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  cloe0626 replied 1 year ago.

hello my name is ***** ***** is the phone call request that you as ask for as soon as you accept i will give you a call

Customer: replied 1 year ago.
Oh I didn't need a call I must have hit that on accident
Expert:  cloe0626 replied 1 year ago.

not a problem no you still need help

Customer: replied 1 year ago.
Customer: replied 1 year ago.
Whatever the problem is I'm sure it's happening in cylinder 1 the most and cylinder 8 it's definitely not the wires or coil packs or spark plugs. Also I have a snap on modis scan tool to help I'm not that good with it yet if you want me to send you any data
Expert:  cloe0626 replied 1 year ago.

yes can you send what information you are getting

Customer: replied 1 year ago.
Can you tell me what you want? The only code is the random misfire but when I go to misfire data it shows cylinder 1 misfiring like 60 times a cycle and cylinder 8 about 30
Customer: replied 1 year ago.
Just now cylinder 1 misfired 193 times and cylinder 8 had 1
Expert:  cloe0626 replied 1 year ago.

can you check compression on cylinder 1

Customer: replied 1 year ago.
it was sorta tricky hard to count how many times it cranks. But I think it has good compression out of about 5 try's it was always between 100 and 180
Expert:  cloe0626 replied 1 year ago.

compression shouldnt drop below 140

Customer: replied 1 year ago.
I also loosened the rockers on cylinder 1 and put 90 psi to it and couldn't hear air coming out any where
Expert:  cloe0626 replied 1 year ago.

then i would agree you have good compression

Customer: replied 1 year ago.
How many revolutions should give you 140?
Customer: replied 1 year ago.
What would make 1 cylinder misfire like that?
Expert:  cloe0626 replied 1 year ago.

run a fuel pressure to test you have already checked the spark plugs correct

Customer: replied 1 year ago.
Fuel pressure was 60 psi and I put a new spark plug in
Expert:  Pete replied 1 year ago.

Your next step here as it looks like compression is good is to have cylinder 1 fuel injector tested.I have seen the injector fail to atomize properly to where it needs cleaned or replaced to correct this fault here.Instead of testing it you can try and swap it with another injector on the fuel injector rail and see if the misfire moves to the cylinder you swapped it with.If it does then this is the fuel injector that needs replaced.If you want the test procedure let me know but this will require a fuel pressure test gauge and a scan tool that can pulse the injector.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete