2003 Silverado running rough

[jharrypope]

I have a 2003 silverado and am having issues. When i first start truck it will miss and sputter and idle will fluctuate for 10 to 15 seconds then will smooth out. when on road at WOT it loses power, feels very restricted, rough runs, misses and the check engine light comes on. Pull code and it is p0151 and p1031. the o2 sensors have been replaced. Any clues as to what i could look for? Could a leak in the intake cause that or a bad fuel pressure regulator? HELP!!!

 

[jharrypope]

forgot to mention, it has a K & N filter on it. LS1 engine. had computer problems in past and had to replace it.

[txab]

I'd certainly check fuel pressure and flow. Changed the filter lately? Check for the presence of fuel at the vacuum line on the FPR

[jharrypope]

has a brand new fuel filter. where is the regulator located? would that cause the problems?

[txab]

Drivers side fuel rail area. Also check all your wiring to and from the O2 sensors for problems

[jharrypope]

ok, will check wiring. would a bad regulator cause those problems though?

[jharrypope]

Ok. I have checked several things: I sprayed the carb cleaner looking for air leak and nothing found. Checked fuel pressure regulator and it was ok, however, I did check the fuel pressure and it's running about 22 psi when at idle. Shouldn't it be in the 50s?

[efritz]

Spec is 55 psi i believe, key on engine off. Shouldnt go down much from there when at idle. Sounds like a pressure regulator or maybe a fuel pump is bad. If the pump has more than 100k on it or is very loud when running, it is likely the culprit.

[Duelin]

Also while you at it since you are running a K&N I would clean the mass air flow sensor.

[jharrypope]

I checked fuel pressure regulator and it's fine. The truck has 175,000 on it and that is original fuel pump. Has new MAF, MAP, o2 sensors.