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2000 Chevy Blazer 4.3 (w) P0300


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burningases
New User

Jul 24, 2019, 8:13 PM

Post #1 of 5 (612 views)
2000 Chevy Blazer 4.3 (w) P0300 Sign In

Wow let me type this again, thanks backspace for that awesome help Mad ANYWAY


2000 Chevrolet Blazer LT 4WD
4.3L Vortec (LU35 - W)
160k miles

At idle I get a p0300 random misfire. With my snap on scanner I see it's cylinders 1-3-5, all of which are driver side of block. at higher rpms, it clears up.
I've had some other issues, this is the hopefully last one before I tackle the 4wd. I've replaced fuel pump, fuel filter, fuel pressure regulator, spider injector is good, rotor & cap, wires, plugs (.060 gap), MAF sensor, other non related parts for other issues. Tomorrow I am pulling the distributor out to check bearings, only thing I can think of is maybe a wobble? I ordered a new one, so that'll also take care of the cam position sensor. Any other suggestions would be appreciated.

Thank you

(This post was edited by burningases on Jul 24, 2019, 8:15 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 25, 2019, 2:39 AM

Post #2 of 5 (589 views)
Re: 2000 Chevy Blazer 4.3 (w) P0300 Sign In


Quote
spider injector is good


How did you determine that?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



burningases
New User

Jul 25, 2019, 3:09 AM

Post #3 of 5 (581 views)
Re: 2000 Chevy Blazer 4.3 (w) P0300 Sign In

1, fuel pressure gauge, 60psi slight drop of a few psi. Also, when I had the intake off to replace the fuel pressure regulator, I pressurized and inspected for leaks.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 25, 2019, 8:53 AM

Post #4 of 5 (556 views)
Re: 2000 Chevy Blazer 4.3 (w) P0300 Sign In

Then you are going to have to examine the data stream to determine what kind of situation you have such as too rich, too lean. See if there are any vacuum leaks on that bank.

Pull the plugs and analyze them too.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
Veteran / Moderator
Sidom profile image

Jul 25, 2019, 10:07 AM

Post #5 of 5 (551 views)
Re: 2000 Chevy Blazer 4.3 (w) P0300 Sign In

If you have a S/O scan tool & fuel pressure gauge, then you can run a injector balance test to make sure they all drop the same pressure amount.
Also look at the fuel trims at idle when it's missing and at higher speeds when it clears up, a high % on the LTFT would indicate a air/fuel problem.
Those trims usually have to be at 25%ish or higher to set a code. You could be at a borderline lean misfire without setting a lean code.






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