Quick background: Check engine light has been on for a while -- At least two years (I know, I shouldn't have let it go for so long). Fault code always came back as a very small Evaporative Emission Leak but tightening the gas cap never kept the check engine light away. The truck ran fine but gas mileage was normally around 12mpg (all city driving in a city where there seems to be a red light every 100 yards) which always seemed on the low end of the 5.7L Hemi's range.

Today I was driving home for lunch and, after driving about 10 miles, there was a 500 yard stretch that the engine felt like it was running really rough, kind of choppy like it was misfiring. I pulled into a parking lot and as soon as I was off the road the engine died. I was able to restart it but it idled extremely rough and would die if I didn't consistently rev the engine to a higher RPM.

My first thought was that I'd gotten some bad gas. I'd filled up the day before from less than a gallon left in the tank (7 miles until empty on the computer) to a full tank. But my wife and I went Christmas shopping later that night and drove all over town looking for a Wii Fit (nine stores with no luck!) and I had to drive to work the next morning and then to a few appointments. So all together I'd gone through nearly a quarter of a tank before the problems started. Just to be safe I put a bottle of Heat into the tank hoping that might clear things up but that hasn't made a difference so far.

These are the fault codes that read on the dash:

P0300 - Random/Multiple Cylinder Misfire Detected
I think this only came up because the engine idled so rough (Maybe from not getting the right mixture of gas/02?)

P0442 - Evaporative Emission Control Leak Detected (Small Leak)
I think this code is new.

P0456 - Evaporative Emission Control System Leak Detected (Very Small Leak)
This is the code I'd traditionally gotten in the past and I'd always read it was likely the cause of a loose or bad gas cap.

It was cold and rainy today so I wasn't really able to check any of the Evap. System for cracked hoses or leaks. The reason I'm posting on here is because it seems like a very small to small leak in the Evap. System shouldn't keep the truck from running at all.

Do you think it's possible the mixture of bad gas and an evap leak could be the cause of the problem or should I just stick with what the fault codes are telling me? I'm open to any input or suggestions you can think of. Is there something more I should try besides heat to make sure it's not bad gas before I spend a lot of time checking every inch of the evap system?

I know it's getting late but hopefully someone is around who can help because I really need my truck back up and running and I need the fix to be as cheap as possible (these things always happen at the perfectly worst times don't they?).

Thanks in advance for any help you have to offer,
Dave

 

The evap leaks most likely won't cause the misfire code. I'd check the hoses and if you don't find any leaks have it smoke tested. On the running rough and misfire that could be a bunch of things, does it do it if you powerbrake the truck?

 

Hi. Does the engine run REALLY bad, like it has a high duration race cam in it? I know it sounds stupid but if is just stumbling or running slightly rough it could be a lot of things. If it is running really bad and you are hardly able do drive it, I think you may have a broken valve spring. When the valve spring breaks, it allows the valve to drop slightly and cause some turbulence in the intake which screws up the MAP sensor readings causing it to run like complete crap. I have had to repair many of these for this problem and if you drive it too long, you will end up with a valve that looks like an S after it is sucked into the cylinder and smashed. 2003 trucks are the only year I have seen this happen on. There are revised valve springs available and I recommend replacing all of them if this is the problem, actually i would recommend replacing them on any 2003 hemi just to be safe. If it gets too bad you will be replacing the engine. Get it checked out or pull off the valve covers yourself, its not as hard as it looks. This is really the only fault with these engines and it was fixed by 2004. Hope this helps.

 

Sorry, I completely missed the other problem you have. Evap codes. I know you checked your gas cap for tightness but did you check the cap itself? They are very common for growing corrosion on the valve inside the cap. You can check this by gently prying back the black clips that hold the white center in while pulling on the center to work it free. If it is bad you will see a bunch of rusty crap in there, if it is clean, snap it back together your problem is elswhere. Another source is by the evap canister under the driver's side of the truck just forward of fuel tank. Get a flashlight and look at the lines, they are common to have dry rot. You may see some slight cracking at the connections where rubber goes onto plastic. Be sure to wiggle them too, if they are cracked bad enough, they will come right off. Otherwise, look under the hood and locate the purge solenoid and track the hoses back paying attention to the short rubber sections for the previously stated dry rot. If you can find no leaks, your NVLD pump may be at fault. It is hard to say without smoke testing your system but some of these checks should rule out some of the easy things.

 

Was talking to the shop foreman at chrysler when I was down there and he was telling me about that. Said it was easy to diag when one came in with a dropped valve though, longblock lol.

 

Unfortunately, you hit the nail on the head st2pd. I was a little worried when I read your opinion because the engine did sound like a race cam and I just couldn't believe that a evap leak could cause this much of a disruption in the idle so I broke down and took it to my mechanic. Broken valve spring on the #6 cylinder. Like you, my mechanic said it is common particularly in 2003's but also added that it happens almost exclusively in that same cylinder. I asked about replacing all of the springs but he didn't think it was necessary. I'm not thrilled about having to pay for the repairs but I want to make sure everything checks out so a $250 problem doesn't turn into a $2500 problem. He said they didn't see any other damage on their fiber optic camera so he's optimisitice that everything else will check out once they finish up the repairs.

I appreciate you pointing me in the right direction guys!

 

If there isn't a huge difference in price I'd have them all replaced. If it's that common of a problem then what happens if you have another one break 100 miles down the road?

 

Im experinceing the same problem with my 03 dodge ram. but im and just have the P0442 - Evaporative Emission Control Leak Detected (Small Leak) code coming up.

I got under the truck and saw that one of the hoses running to the EVAP canister didnt have the stock hose clamp on there becuse it was broke, is it possble for this to throw that code.

also it has had a rough idle and hesataing off red lights and stops. Also running down the highway if will jump it RPM from 2,00 to 3,000 then back down to 2,000 then back up and so on and so forth. is that something that can be caused by this?

 

You also re-started an old thread.

But to answer your question, yes, the evap can and hoses under the truck and right before the fuel tank but all be connected and have no holes or other faulty issues