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P0300 code

12K views 8 replies 5 participants last post by  2011 GMC Crew 
#1 ·
ok fellas, i really need some input on this problem. my truck is a 97 silverado with the vortec 5.0 and 4L60E tranny. problem is a horrible miss in the motor. engine light was not on but hooked my scanner up and the P0300 code came up. i replaced the plugs, plug wires and coil to no avail. didnt make a difference at all. has no power what so ever. truck has 169k on the clock and is all stock with the exception of a 3" flowmaster and a gutted cat (was like this when i bought it last year)....... anybody have any suggestions on what i can do
 
#2 ·
Maby an intake gasket leak? Im Not sure how to check for it other then to open it up, i hear they fail commonly on these engines....

Multiple Clogged Injectors?

I just had a problem with my truck but the misfire was only 1 cylinder, i did everything you did but it ended up being the injector.

Good Luck
 
#3 ·
I replaced the intake gaskets right after i bought the truck last april. And that was the first thing i checked. Thank you for reminding me though! A good friend of mine from the dealership told me it sounds like injector trouble. Just like you had mentioned. Im gonna check ebay for a set of injectors. Thanks for the reply and help!
 
#5 ·
harper
I did overlook the cap and rotor. Guess since i replaced them when i did the intake gaskets i figured they were still good. One of the first things i should have checked though. Thanks for bringing that to my attention. I will definitely try that next!!
 
#7 ·
Disconnect the cat in the front and see if it runs better. The other thing you could check is the egr valve the o2 sensor duel filter. Injectors you can check while its running put a rod to the end of one and listen to the other end for a double tick. That means it's good. I'm going thru this problem now and it turned out to be a clogged cat on one bank. Started with a p0300 code. Ran horrible could make it up a hill, took cats off and runs fine. $350 in diagnosis later.
 
#8 ·
Well sorry guys it's been till now that I am posting what I did to fix the problem. Hard to get a break from work working 7 days a week on 3rd shift. Anyways... I ended up replacing injectors #3 and #7 as they were found to be bad. (Glad I have buddies that work at the GM dealership!!) Wasn't too bad to replace them but she runs so much better and mpg has improved a smidge. For it having 170,000+ miles on it
 
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