And also a constant is that it is always only cylinder 5??? If true I can't see something like a weak fuel pump affecting only one cylinder.
P0305 error
- Thread starter PeachesSabrina
- Start date
And also a constant is that it is always only cylinder 5??? If true I can't see something like a weak fuel pump affecting only one cylinder.
So update, I have misfires on CYL(s) 4,5,6. I had about any where from 500 to 2k misfires on each cylinder, but only at startup and the engine is cold. After startup no misfires what so ever, in fact I just took a 150mi trip and after startup there were no misfires. The RPM'S peak at about 950 and then after about 2 min settle down to about 600 RPM's
CYL(s)1,2,3 are working fine BTW
CYL(s)1,2,3 are working fine BTW
The GM 4.2L LL8 Engine Intake Manifold uses unique, Low Torque "Trapped" Fasteners requiring a MAX of only 89 Inch Pounds because they bottom out and only serve to squash what would ordinarily be "new and plump" Rubber "O" Ring Style Gaskets in Three Sets shaped like sideways #8s along the interface of the Intake Manifold Flange.
Due to the 'pendulum' like action of the heavy Throttle Body being on one side, counter-balanced by the heavy PCM diagonally on the other... Engine and Body Vibrations will cause the Intake Manifold to rock back and forth, making the "O" Ring Style Gaskets flatten out over time and allow unmetered Air to by-pass the PCM Engine Management System (The LL8 Motor is an Air Weight-Flow dependent system NOT Fuel Dominant) and this can cause Random Engine Misfires.
On Early Model TBs & Envoys the upper Center-Most Fastener is hidden under a Small Rubber Elbow Hose connecting the Intake Plenum to a Port in the Aluminum Engine Head. Be careful not to damage that little fellow during its R&R. The Fasteners located closest to the Engine Firewall have been the source for inventing New Swear Words due to the difficulty in accessing them with a Small 3/8" Ratchet, a Short Extension and Little Universal Adapter to wend its weary way around and on top of that small IM Bolt Head.
You could try carefully tightening up any possible loosened Fasteners along the IM Flange... but avoid freelancing with this action. The same kind of Fasteners apply to the Engine Head Valve Cover. Unlike the Old GM Valve Cover Cork Gaskets ...ALL of these Fasteners sport a Very Short Thread Line (M6X1.00X12mm) that can bottom out suddenly and very easily get Snapped Right Off if they get Tightened TOO Aggressively. If anyone has already tried this and you discover that the Fasteners remain in place... but "spin free" when being tightened...do not despair. There are two specific Threads addressing how to perform this repair:
gmtnation.com
gmtnation.com
Due to the 'pendulum' like action of the heavy Throttle Body being on one side, counter-balanced by the heavy PCM diagonally on the other... Engine and Body Vibrations will cause the Intake Manifold to rock back and forth, making the "O" Ring Style Gaskets flatten out over time and allow unmetered Air to by-pass the PCM Engine Management System (The LL8 Motor is an Air Weight-Flow dependent system NOT Fuel Dominant) and this can cause Random Engine Misfires.
On Early Model TBs & Envoys the upper Center-Most Fastener is hidden under a Small Rubber Elbow Hose connecting the Intake Plenum to a Port in the Aluminum Engine Head. Be careful not to damage that little fellow during its R&R. The Fasteners located closest to the Engine Firewall have been the source for inventing New Swear Words due to the difficulty in accessing them with a Small 3/8" Ratchet, a Short Extension and Little Universal Adapter to wend its weary way around and on top of that small IM Bolt Head.
You could try carefully tightening up any possible loosened Fasteners along the IM Flange... but avoid freelancing with this action. The same kind of Fasteners apply to the Engine Head Valve Cover. Unlike the Old GM Valve Cover Cork Gaskets ...ALL of these Fasteners sport a Very Short Thread Line (M6X1.00X12mm) that can bottom out suddenly and very easily get Snapped Right Off if they get Tightened TOO Aggressively. If anyone has already tried this and you discover that the Fasteners remain in place... but "spin free" when being tightened...do not despair. There are two specific Threads addressing how to perform this repair:
Need Help With Stripped Coil Pack Retaining Bolt Insert
I have a 2003 Trailblazer EXT with 209,000 miles on it. I have changed the plugs twice every 100,000 miles with no problems. The other day it started running rough and was getting a flashing "Check Engine Soon" light. I ended up finding the #6 coil pack not seated on the plug because the hole...
gmtnation.com
NEED HELP - Intake manifold broken bolt
Ok here's my issue. I am replacing and engine in my 2003 GMC Envoy and as I was switching over the intake manifold a bolt snapped off in the new engine block. I have drilled it out and just wondering how to get the broken bolt free from the manifold and if it's possible to replace the bolt...
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I was just about to postulate about the intake manifold and while doing so I see @MRRSM has drawn first. Good thing as he does a much better job of these things than do I!!
One last thought folks, what if it's the battery thats causing the misfires. The reason I am wondering g this is it was warm today here in the PNW and I had the A/C running full blast when I turned the key. Now when I turned the ignition it didn't crank, when I turned the A/C down she started right up.
Tankcruiser
Member
These are the Most Common PXXX Causes...in their Order of Diagnosis:
www.700r4transmissionhq.com
...and concurring with @Tankcruiser on checking the Grounds... check out @Realism 's Epic "Ground Breaking" Thread for Images & Diagrams to assist you:
gmtnation.com
Chevy Trailblazer P0305: Cylinder 5 - Misfire Detected | Drivetrain Resource
P0305 is a fairly common trouble code with the Chevy Trailblazer. It's and OBD2 code and stands for: P0305: Misfire Detected → Cylinder 5 P0305 is certainly a cause for concern, and should be considered a threat to the drivability your Trailblazer. The nice thing about P0305 is that it's a...
www.700r4transmissionhq.com
...and concurring with @Tankcruiser on checking the Grounds... check out @Realism 's Epic "Ground Breaking" Thread for Images & Diagrams to assist you:
Electrical Ground locations
While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L. Credit goes to Wex...
gmtnation.com
Attachments
So it appears that the issue was the positive connection on the battery. Apparently when I replaced the battery the tech stripped the positive connection and it was loose. It was making a connection but not a great one. The post was replaced and it sounds great, no misfires.