Hi. I have a 2004 Chevy Silverado 2500 6.0 and I’m having a hard time finding the problem with it. When it’s running it will randomly die down and almost stall at idle. Or when I’m driving at light throttle it will buck and bog, but as soon as I give it heavy throttle it gets right out of it and drives fine. But again as soon as I let off the throttle it will run bad. I have previously had problems with the throttle body getting oil residue all through it so I installed a catch can but it fills up with nasty residue fast. Just looking for somone to put me in the right direction as I am clueless at this point. Thanks
2004 Chevy Silverado 2500 with the 6.0 running rough
- Thread starter Chevy2005
- Start date
Welcome to the forum, from Oregon.
In no particular order, First: Is there any CEL? Second: Age of ignition related components? Third: What do the plugs look like? May need to pull plugs and keep in cylinder order and post pics of the business end. Fourth: While plugs are out, do a compression test. Fifth: Before plugs removal, attach a Live Data scanner and see what the readings are for long term and short term fuel trims. Need to monitor O2 sensor activity. Sixth: Need to know what the fuel pump pressure is. Can attach a long enough hose to the gauge and run hose out the back of the hood and tape to w/s and see what the fuel pressures are during different load conditions.
The key will be if you have any CEL. Check Engine Lights. That can help pinpoint a single cylinder if is the culprit and also if is fuel trims or sensors related.
I have a 2004 Chevy Silverado K2500HD 6.0, so I have a personal stake in this outcome.
Had you done any previous work on the truck before this problem? Had any shop look at it yet?
You said, "having a hard time finding the problem with it", so that leads me to believe you have done some research or attempted some work on it.
You may have a pcv system problem and need the valve covers replaced. There are updated valve covers out there for pcv problems related to the original valve cover/pcv design.
In no particular order, First: Is there any CEL? Second: Age of ignition related components? Third: What do the plugs look like? May need to pull plugs and keep in cylinder order and post pics of the business end. Fourth: While plugs are out, do a compression test. Fifth: Before plugs removal, attach a Live Data scanner and see what the readings are for long term and short term fuel trims. Need to monitor O2 sensor activity. Sixth: Need to know what the fuel pump pressure is. Can attach a long enough hose to the gauge and run hose out the back of the hood and tape to w/s and see what the fuel pressures are during different load conditions.
The key will be if you have any CEL. Check Engine Lights. That can help pinpoint a single cylinder if is the culprit and also if is fuel trims or sensors related.
I have a 2004 Chevy Silverado K2500HD 6.0, so I have a personal stake in this outcome.
Had you done any previous work on the truck before this problem? Had any shop look at it yet?
You said, "having a hard time finding the problem with it", so that leads me to believe you have done some research or attempted some work on it.
You may have a pcv system problem and need the valve covers replaced. There are updated valve covers out there for pcv problems related to the original valve cover/pcv design.
Yes. I have replaced spark plugs and wires all is good. I have not checked fuel pressure but I will have to. I do not have any check engine light at all so I’m trying to investigate further. I would hope that the fuel pressure is good as the fuel pump is only 6 months old. I would agree with a possible pcv problem because of the excess oil residue coming out of the valve cover so I’ll have to start there. I haven’t had any shop look at it yet as I’m pretty handy when it comes to working on it. I’ve done new plugs and wires, oil change, cleaned out throttle body and mass airflow sensor. But no fix in the problem. I’ll have to start by pulling the valve covers and check it out. Thanks
If the valve covers are original, replace with the new design. What did the old plugs look like? The pcv problem is likely not related to the running problem unless fouling plugs but enough misfires should have triggered a CEL. If you used a generic aftermarket fuel pump, they are always suspect. Use Genuine GM, AC Delco or Delphi and should be good.
Again, a live data scanner can be your friend. For quick live data info I use this and it costs $70 at Amazon, Foxwell NT301
https://www.amazon.com/FOXWELL-NT30...-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1
If I really need to get deep in a vehicle, I have an Autel scanner I use.
The plugs when I pulled them did not look bad. They looked as they should but i still replaced them. There isn’t a check engine light but there was a code when I plugged in my scanner. It was P0103 Mass or volume air flow circuit high input. It all comes back as mass airflow sensor but I had a spare laying around that I know is good so I put it in and same problem. Nit sure what the next step would be toward that code. Thanks
P0103 code indicates high air intake signal. Faulty MAF sensor, wiring issues, or vacuum leaks may trigger it. Symptoms include engine hesitation, reduced fuel efficiency, and check engine light. Diagnose using OBD-II scanner, inspect MAF sensor, and monitor live data.
Check all related wiring and connections. Have you checked for vacuum leaks?
Check all related wiring and connections. Have you checked for vacuum leaks?
I have checked all of the wiring yes. So far it looks fine. I know the maf is fine. So I’m not sure. I have looked around for vacuum leakes and listened for them but nothing stands out. The truck runs fine for the most part when going down the road but when I let off the throttle and come to a stop it idles terribly. So I’d like to say possibly a vacuum leak? Not sure. Thanks
AuroraGirl
Well-Known Member
the MAP sensor is required for MAF rationality checks. The MAP sensor has an O ring that doesnt fit all that tight, remove the MAP sensor and check out the o ring on it. I had a bad MAF sensor, the sensor still read but it increasingly lagged behind what it should have been based on the new ones readings, it would periodically throw a code but it would operate startup usually just fine.
The new valve cover, and this , would be wise in a cold place. But the valve cover is the biggest part. If its burning oil such that its constantly sucking liquid Oil, that will definitely cause driveability issues. but the catch can should be minimizing that
no check engine light DOES NOT mean no codes. So no offense but you need to put a scan tool to it.
there also a TSB for oil burning in cold climates that see freezing temperatures, that amount of oil burning is excessive, and it replaces the oil cap on the passenger valve cover. The cap incorporates a relief so if the PCV line is frozen it vents excessive pressure
The new valve cover, and this , would be wise in a cold place. But the valve cover is the biggest part. If its burning oil such that its constantly sucking liquid Oil, that will definitely cause driveability issues. but the catch can should be minimizing that
Did not know about the oil fill cap but each time I have done the valve cover updates, I insisted on new cap and tube.
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AuroraGirl
Well-Known Member
Tube? like the one between the valve cover and cap? I want to eliminate mine, but valve cover doesnt leak so i dont want to do it tell it needs it lol
Despite this calling for -30 degrees and colder weather, I have a feelinng the same thing happens at much warmer temps because the air from the PCV valve is going to be under vacuum, lowering the freezing that its already under for water by far, AND that its vapor which has a high surface area that can lose heat quickly, going through a small orifice (2003 or 4+)
The 2003 i think would have a rattler Pcv
I like the tube sticking up there. Makes it easier to refill after oil change. I know the tube can shift a little when trying to remove cap. I just use both hands and grab the tube to keep from shifting.
AuroraGirl
Well-Known Member
I just like the look without it
but im a hypocrite, if you open my hood youll see this
I wanted to see if the 3800 extensions (for the engine cover) worked on this.. they do lol. The cap unscrews the top 2 with it because its tighter up there than those are haha.
Good thing you explained the pic. I was getting ready to call you out.....
AuroraGirl
Well-Known Member
i need one of those steps that go on the wheel so i can reach things like the oil fill betterGood thing you explained the pic. I was getting ready to call you out.....
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Hi there,
Still having problems.. I pulled the map sensor out and it was dirty with oil, so I cleaned it very well and put it back in. It did seem to run a little better but still didn’t fix the problem. It’s reading 12 inHg on my scan tool. I checked the fuel pressure and it’s at a constant 55-60 with key on and at idle. I took a look at my fuel trims on it aswell and there is one odd ball. Both of my stft are at 0 but ltft 1 is at -3.9, but the ltft b2 is at 25% and seems to stay there. From what I’ve researched the 25% is not an ideal number to be having. Not sure if that is a o2 senor problem and what one it would be to cause only one bank to have a high fuel %. Any ideas? Thanks
The fact that both STFT are at "0" tells me there may be a communication problem. I have experienced the drivability problems you described, for your truck, on my own 2005 Tahoe 5.3 and was O2 sensor problems but the live data reading may be an indication of a need for a computer relearn. There are many videos at you tube, "2004 Silverado computer relearn", to look at. May also want to see if have exhaust back pressure.
I have already reset it about 2 hrs ago. Still no change. It seems that the numbers are frozen at those values but that could also be my cheap scan tool. From my research I thought that the closer to 0 it is the better so I figured the banks at 0 are good. I figure that it could be the bank 2 o2 sensor (passenger side) but I’m not completely sure.
To follow up on that, I did notice a exhaust leak about 2 feet behind the o2 sensor but it is on the x pipe so both banks should be effected but it appears that only bank 2 is having problems. I might just have to send it to the shop. It’s driving me nuts
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