1998 yukon Mystery p0300 and rough idle still

[OilBurner2003]

Yessir, the wires all looked good as far as I can tell. It’s hard to move the harness when it’s connected to everything, I will try to get another look when the o2 situation is handled.

Just the outer plastic loom was melted - didn’t burn through to the wires?

 

[OilBurner2003]

Yessir, the wires all looked good as far as I can tell. It’s hard to move the harness when it’s connected to everything, I will try to get another look when the o2 situation is handled.

Was going back through some codes, noticed something strange. Somewhere in the past had a code P1351, to my knowledge, is the ICM? Which if I'm correct, controls the spark timing...Scanned the computer with a different scanner and got that. Now the code is nowhere to be found. What the hell could that possibly mean?

 

[exp500]

Don't worry if it is gone. Dist, ICM, Coil, Long crank time potential causes.
About time you fix P0300. What is fuel pressure key on eng off? At Idle? How long till it drops 5 Lbs?

 

[OilBurner2003]

Don't worry if it is gone. Dist, ICM, Coil, Long crank time potential causes.
About time you fix P0300. What is fuel pressure key on eng off? At Idle? How long till it drops 5 Lbs?

Still got P0300 haha! On all cylinders still, computer just doesn’t wanna throw a code for it.
Key on is 59 PSI, Idle is 55. I haven’t measured the drop ever since I changed the injectors, it took like a hour to lose 1 PSI with key off.

 

[exp500]

Fuel pressure is low, most likely fuel pump. Book says 60-66. I've had 2 that missed slightly at 60 under load.

 

[OilBurner2003]

Fuel pressure is low, most likely fuel pump. Book says 60-66. I've had 2 that missed slightly at 60 under load.

That’s strange, I’ve had mixed answers here that say 55 is good running PSI. Fuel pump is a year old, it was a Delphi.

 

[exp500]

That’s strange, I’ve had mixed answers here that say 55 is good running PSI. Fuel pump is a year old, it was a Delphi.

Newer vintage 55 is OK. RTFM

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

GMT400 CK Manual Project - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMT400 CK Manual Project The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

67-72chevytrucks.com

 

[OilBurner2003]

Newer vintage 55 is OK. RTFM

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

GMT400 CK Manual Project - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMT400 CK Manual Project The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

67-72chevytrucks.com

New plan, gonna throw a new ICM in there just for a test, can’t hurt to try. Should have results when it gets here.

 

[exp500]

Would be better to see fuel trim Numbers while on hiway, as well as misfire counts at speed.If misfires rise alot as speed increases(more than linear progression).Trying to rule out fuel pump/regulator. slow down on parts changing till you gave a proper fix figured out. Adding unknown parts only extends troubleshooting time. Your scanner live data is best friend, not at idle in driveway.
I have a long hose in my fuel pressure gauge so I can stick it on windshield.

 

[OilBurner2003]

Would be better to see fuel trim Numbers while on hiway, as well as misfire counts at speed.If misfires rise alot as speed increases(more than linear progression).Trying to rule out fuel pump/regulator. slow down on parts changing till you gave a proper fix figured out. Adding unknown parts only extends troubleshooting time. Your scanner live data is best friend, not at idle in driveway.
I have a long hose in my fuel pressure gauge so I can stick it on windshield.

Can’t take it on highway, misfires too hard. Fuel regulator is new as well when injectors were done.