p0300 Hard to Start, Rough Idle, Burning Rich - Solved
Junior Member
Joined: Nov 2018
Posts: 1
P0300
Just bought use h3 103k miles driving good then few days multiple misfire in clinder 5 . Now missfire in multiple cylinders change spark plugs but the worst now I driving 35mph with 4K rpm like I be in low gear if I do 50mph my rpm are up to 4/5k and not going down :/ any solution?
Senior Member
Joined: Feb 2016
Posts: 172
Now if the FPCM take a crap you will have similar issues, and codes as well.
Junior Member
Joined: Jan 2023
Posts: 1
I just fixed a p0300 and this time it was found to be a fuel pressure regulator. The regulator was spitting fuel directly back in to the intake manifold through the vacuum tube making the vehicle hard to start, rough idle (flooding), and burning rich. If you have these symptoms, it's super easy to verify and fix. You can easily check this by following a diagnosis on a similar vortec engine here: https://www.youtube.com/watch?v=S5Jrwa64LDU
Super Moderator
Joined: Jul 2007
Posts: 13,056
From: Boat Town USA MI
Just pulled the little hose to the fuel pressure regulator and a lot of gas was pouring out. 2003 Hummer H2. Rough idle, P0300 code Multiple Random Misfire. I changed spark plugs, wire prior to the misfire and I thought it was a bad coil. Switched those out too. Ordered the part should know soon if that is the issue! Fingers crossed 🤞🏽
Let me point out that you just tacked on a comment to an Old As DIRT Thread from 2018.... that is near SEVEN YEARS AGO! Let's avoid that from here on out, not what we do here. READ: Old Threads/'Necro-Bumping'
Thread
Thread Starter
Forum
Replies
Last Post
Justinh
PRIVATE For Sale / Trade Classifieds
4
Jan 9, 2016 11:18 AM