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2003 Silverado running rough


jharrypope

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Posted

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!!!

 

Posted

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

Posted

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

Posted

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?

Posted

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.

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    • I will admit I haven't experimented much with pressure drops beyond the numbers I put in and part of that is that the numbers I used are fairly low and then found out it would trigger regardless at that 35 psi. Having said that I had tried before had changed the placard pressures and being that I have a 1 ton set to 80 on the placard for the rear I believe it triggered close to 60, the front I don't recall now for sure but thought maybe it could get close to 45 from that factory 60 placard pressure. So I never did figure out if it was a number of psi from placard pressure to the alarm or a percentage of the total placard number as some figured it was like a 25% drop from placard pressure would trigger it. So as to try and answer your question, I believe I set the placard pressure on the front to 47 or so and while I run the front tires at 40, they have dipped below that some if its colder and I haven't put "winter air" in yet and never once have had the front alarm go off. I would say that the answer your looking for is no, that if you set your placard pressure to 45, you have a certain amount of room to drop below that pressure before the alarm will go off.    The pressures you decide to run in your truck, that ends up being what makes sense to you based on what your carrying in your truck or if towing, then have to bump them back up to something that will carry the load in the rear and the fronts typically left at the same pressure. It all comes down to that chart I put the link to and using an accurate roadside scale to be your guide, both unloaded and then loaded to know your minimum safe pressures.    I just wish GM would allow a person to change the readings for the tire pressures to the English system of pounds as I have to look at that goofy metric reading that will never ever jive in my head and will go over and change it just to figure out what they are if need be and then change it back. 
    • That part I understand, that the dealer can do it. But I'm not understanding why updates that were available to the truck since it left the factory, or the dealership originally, would not still be available to it without dealer intervention.   I'm thinking along the lines of recalls. They stay available until they are completed, regardless of whether they are in warranty or not, or in the hands of the original owner or not. Why not updates as well, especially since some of those can be safety related also?
    • That's good to know, but I don't think I'll even be running them under 45 in the rear  unless it's on the sand or something but will only be for a short distance anyways!    I didn't read all the instructions in the booklet yet, but do you know let's say I set the rear psi on the placard to 45, will the warning light come on soon as it drops under 45 or is there a percentage it has to drop from the set value before the warning light is triggered?
    • That's bad.  Like, its probably destroying the stub axle the CV slides into.   Do you have a proper lift installed with differential lowering brackets?  Did you install AT4/Trail Boss factory CV axles?  
    • Hot? New Jersey? Today? I was working on my old 2000 Silverado 1500 today. Believe me, it was boiling hot today. As it has been.
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