Hey everyone first off love the forums, have helped me out quite a bit!! Heres my issue, first off im not a mechanic but am very smart and mechanicly inclined. OK. So i have a 2006 Dakota V-8 4.7 2wd, and was having a very rough idle, would go up and down between 1-2 rpms, but drove fine. so cleaned the IAC valve. idled perfect!! then put in drive right after and started to bog down, no power, until you got up to 20-30 mph. The more we drove it the better it got, but now when you start it it acts as though its not getting fueling and sputtering out, and wont even stay running. i changed out all the spark plugs and cleaned the coil packs up. then i checked the fuel pressure in the rail and nothing( by punching the stem with a screwdriver) all it does is spit out a little fuel and thats it. checked the fuse and relay and they are good. is my fuel pump out or could it be the fuel filter. i had taken it to autozone last weekend and got these error codes..p0113,p0171,p0300,&p0508.. please help.

 

I think your IAC valve is shot. Sounds to me like intermittent failure. I would replace it and see if that solves your issues. P0508 = IAC Sensor issue. P0113 = Intake Air Temperature (IAT) sensor issue, but that may be related to P0508. P0171 means that the engine is running to lean, and P0300 means random misfires. Both of those are most likely being caused by P0508, and maybe the P0113.

Replace the IAC motor/valve first. If you still have issues, replace the IAT sensor. If memory serves, the IAT sensor isn't very expensive.

 

Thanks for the input and that will be the next thing i replace. i bought a new MAP sensor and its 90% better. After running it for awhile it still has a little a little bit of a rough idle but not like before. Guy at Autozone said it will take some time before the computer recognizes the new sensor, is that true? When i get paid Ill probably go ahead and change out the IAC valve which is like 40 bucks and the temp sensor is 11. just hit 110k anyhow. What you think about changing the o2 sensors as well?

 

Using the "shotgun" method of repair (shooting a lot of parts at the problem indiscriminately) can use up more than one paycheck and still leave you with the same problem. Most of the time, if you have sensor problems, you'll find that identified by seeing a Diagnostic Trouble Code (DTR) with a diagnostic scanner/reader. If you don't have anything showing (you can have codes stored on the computer without a Check Engine Light on) on the scanner, you might have a problem with a component that the computer can't get any information on, like the high voltage part of the ignition, or the fuel system. You said that you checked the high voltage end (changed plugs, etc. & often, if a coil starts to malfunction, you'll get a misfire code) and then had a poke at the fuel rail to check fuel pressure & found very little. I'd get a pressure gauge on there just to make sure - it obviously gets enough fuel to start, but if the pressure is marginal, the engine won't run well. With the gauge, you'll be able to see what the pressure is and how long it holds this pressure once you shut the engine off & if it's generally low & drops off to almost nothing once you shut the engine off, I'd tend to look at the fuel pump (it could be pumping well but have a bad check valve or regulator).

Throwing a couple of hundred dollars at sensors won't fix a fuel problem, so get the obvious checked first, fuel pumps aren't cheap and winter's coming, so it'll get harder to work in your driveway or garage.

 

Plus, installing a new fuel pump is a pain because its in the fuel tank which would require to you to either drop the tank completely or unbolt half the bed and raise it back...either way something I'd try to avoid doing unless I new absolutely sure that was the issue.

 

Well not even 2 weeks later i couldnt even get it to start. turns out that i had mud and water in the gas tank. ended up having to replace the fuel pump thankfully my full coverage insurance covered it!

 

Well that would certainly be unexpected unless you knew that the truck had been used for off-roading. It's good that you found that, I hope none of the issues migrated to the injectors.

If the truck had been in a partially submerged situation to get the mud and water into your fuel tank, I'd be concerned about where else there might be water, like the differentials, t-case, and transmission. I would be checking the condition of the oil in each and maybe even change them at the first opportunity.

 

Did you buy it used? Could have been a flood vehicle.