Hi I have a 2002 GMC Yukon 1500 SLT. Car was throwing a misfire on cylinder 3 for awhile, I replaced the fuel injector and that cleared the problem up for about six months. Now the same problem and code is appearing again and I am also getting a PO200 code as well. I can't believe the fuel injector went bad again and now I am thinking it might be the PCM? Any help would be appreciated. Thank you.
Misfire Cylinder 3 and PO200 Codes
- Thread starter windsor21
- Start date
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BubZX
Senior Member
when u changed the injector did u replace the spark plug as well? spark plug may have went bad.
t_ahan
Full Access Member
I just went through misfire diag. N after checking everything and not finding any faults I pulled the injectors for flow and leak testing cuz I found when I pinch the fuel return n feed lines I still drop pressure out of spec and the regulator(aeromotive#13301) was not leaking and they have great flow and not leaking...
This misfire p0300(cyl 4,6,8) was holding me back from breaking in my new motor so I had to find it with no more than 5min run time cycles and it was burnning me out!
But finally when I fired her up after injector tests I noticed my the bank 2 o2s` mv jump out of spec so I pulled them out to test n I thought since its the same bank as the mifires and the o2s is already out let me start her up and verify the cats not clogged!
Well the truck ran smooth and the throttle respone was sharp n crisp like it should be ! The o2s tested good so to confirm the back pressure issue I went to put the sensor back in n saw rich looking platinum flakes every where and decided to pull the rear o2s n stick my bore scope in to see behind and WOW 2 CLOGGED CATS!
First time i have not gotten any warning symptoms from failing cats.....I believe leaky injectors and oil consumption/contamination can accelerate cat failures
I just thought I would share that cuz I kno I could have saved alot of diag time if I would've done a 2min check b4 testing everything else.
Hope you find it!
This misfire p0300(cyl 4,6,8) was holding me back from breaking in my new motor so I had to find it with no more than 5min run time cycles and it was burnning me out!
But finally when I fired her up after injector tests I noticed my the bank 2 o2s` mv jump out of spec so I pulled them out to test n I thought since its the same bank as the mifires and the o2s is already out let me start her up and verify the cats not clogged!
Well the truck ran smooth and the throttle respone was sharp n crisp like it should be ! The o2s tested good so to confirm the back pressure issue I went to put the sensor back in n saw rich looking platinum flakes every where and decided to pull the rear o2s n stick my bore scope in to see behind and WOW 2 CLOGGED CATS!
First time i have not gotten any warning symptoms from failing cats.....I believe leaky injectors and oil consumption/contamination can accelerate cat failures
I just thought I would share that cuz I kno I could have saved alot of diag time if I would've done a 2min check b4 testing everything else.
Hope you find it!
Last edited:
sting454
TYF Newbie
Fuel pressure regulator ng. Had exact same problem with my 97 yukon
