P0300

[jjaymoore]

Checked grounds, no other codes. I realized earlier that I can use the torque pro app on,my phone to try to isolate to which cylinder(s) are misfiring. So hopefully I,will,figure something,out,in the am.

 

[Doubeleive]

check fuel pressure I guess would be next and then on down the line
i.e.
If ignition and fuel delivery appear to be okay, that leaves compression (or the lack thereof) as the underlying cause of the misfire. The air/fuel mixture won't fire normally if compression is leaking from the cylinder due to a burned exhaust valve, bent valve or leaking head gasket.

A leakdown test or cranking compression test can be used to see if the cylinder is holding or pumping up normal pressure. Low or no compression in a cylinder means the head will have to come off so the leaky head gasket or bad valves can be repaired.

 

[ivin74]

Pull every plug back out and inspect them chances are 1 might be broke. I ran into this issue when I changed them out and during the installation on one of them the ceramic coating was cracked and was doing them samething ur truck is doing

 

[jjaymoore]

Well guys I am glad to say that my misfire issue has been resolved, and at the same time I am embarrassed to admit that I made a rookie mistake. It was around midnight when I got my header installed and put the new plugs in. And being as I was tired and I havent had a plug gap issue with delco iridiums in years, I threw the plugs in without checking gaps or even really taking a look at the new,plugs. I mean, they were brand new in the box right?! Well when I looked at my misfire coy,re on torque pro, they were all over the place on,multiple cylinders. So, I started pulling,plugs and checking them. Well wouldn't you know it they were tapped at maybe .010! Regapped plugs and now misfire count is steady at zero, where it should be.

Thanks to everyone for the inputs. It really helps sometimes to have people to make you think differently about an issue! Guess I will get a new log today and send it to black bear, since my current tune is based off of a log with those bad gaps.

 

[ivin74]

Well guys I am glad to say that my misfire issue has been resolved, and at the same time I am embarrassed to admit that I made a rookie mistake. It was around midnight when I got my header installed and put the new plugs in. And being as I was tired and I havent had a plug gap issue with delco iridiums in years, I threw the plugs in without checking gaps or even really taking a look at the new,plugs. I mean, they were brand new in the box right?! Well when I looked at my misfire coy,re on torque pro, they were all over the place on,multiple cylinders. So, I started pulling,plugs and checking them. Well wouldn't you know it they were tapped at maybe .010! Regapped plugs and now misfire count is steady at zero, where it should be.

Thanks to everyone for the inputs. It really helps sometimes to have people to make you think differently about an issue! Guess I will get a new log today and send it to black bear, since my current tune is based off of a log with those bad gaps.

Glad you fixed it, enjoy the holidays

 

[Doubeleive]

closed

 

[jbyler]

I have a 2003 GMC Yukon Denali 6.0 V8. Just had the ECM unit sent to ACE in Florida > they said it was friend and irreparable and couldn't fix it, so bought a refurbished one from them. Mechanics installed the new one (they also properly removed it), replaced all of my fuel injectors (AC Delco), AC Delco spark plugs and wires, brand new Interstate battery and AC Delco fuel filter. We also replaced a bad coil prior to all of the new change outs noted above. Runs like a champ now, but took it on the highway yesterday and at 67 mph, the engine light begins to blink. There is nothing noted as far as ride>runs smoothly and nothing noted on the tach. When I back down to 63 mph, the engine light stops blinking. Anyone have any ideas? P0300 "random misfire" code>>same code as before I changed out the whole ECM, plugs, wires, fuel injectors... My issues were that the car began misfiring bad, sputtering, low power mode, etc...and finally no go. So, I found a great mobile mechanic team who came over and helped me finish installing the injectors first and remove the ECM.

Also, the driver door controls don't work when the door is open>only when closed > separate issue...anyone out there have the same issue and what did you do to resolve it? Some say door wire harness, some say bad ground...?? Thanks for any help.