Hello all,

I just got my first ram a few weeks ago (2009 1500 5.7 Hemi) and the CEL came on a few days after I picked it up from the dealership

I am not so worried about the p1521 code (wrong engine oil) as I can hopefully do an oil change and fix that.

But these other ones are giving me a headache. So far I have determined that the EVAP small leak code (p0456) is unrelated to the lean condition (p0174) and misfire codes (300 & 303). I did this by disconnecting the EVAP vac line just past the throttle and plugging it. After doing this the lean code came back (I also put a vac pump/gage on the removed line and it held a vacuum, so the EVAP solenoid looks to be good). I have sprayed some carb cleaner around in various places to see if I could find a vacuum leak to no avail. I was able to see my long term fuel trim numbers and they were high on both banks, but highest on the side with the lean O2 condition (bank 1: 22.7% and bank 2:30.5%)

I was originally thinking it was the O2 sensor in bank 2 but seeing the high trim in bank 1 I am now thinking there is another issue. I see that the PCV valve is on the bank 2 side, so maybe that would have a bias for leaning out that side if it was bad?

The engine runs fine (just towed a friend's Viper home from the Chrysler show in Carlisle today, got 13 mpg towing, 21.5 on the way down). The only time I am leary is at idle I can feel the engine sputtering a bit.

Is there an easy way to test the fuel pressure to be sure its just not low?

I also replaced the gas cap hoping it was the source of the p0456 code but that did not take it away.

The only other thing I can think to mention is that the MDS seems to act kinda funny. It will come on just fine for a while and then it wont come on unless I just let off of full throttle and it will go off after a second or two even while coasting.

Any help would be appreciated. I really like this truck, but these engine troubles are bumming me out.

 

Have you pulled out and inspected the spark plugs? Do the plugs on cylinder 3 look noticeably different from those on other cylinders?

-Rod

 

the MDS is acting up due to the "wrong oil". The other symptoms could be due to a worn out cam.

 

Now that I have a nice scanner tool I have been able to see the fuel trims live. They showed that after about 1500 rpm the fuel trims go back to normal. This also corresponded to whenever the manifold pressure went up from opening up the throttle more. So, when the manifold vacuum was low the fuel trims went back to normal. This points to a vacuum leak from the diagnostic knowledge I know. It also explains why I am not getting horrible fuel economy/power and why it only runs rough at idle.

So, for now the plan of action is to replace the intake manifold gaskets, the fuel injector o-rings and the PCV valve. Will update if this fixes the problem.

 

Ok, so I have replaced the injector o rings, the intake manifold seals, the PCV valve, and the MAP sensor.

Still getting high fuel trims and rough running below 1500 RPM. No idea what to do next.

The reason I don't think its mechanical is because of the fact that the engine runs fine when I am accelerating. I would think that if the cam was bad or the injectors were clogged or the fuel pressure was low or the plugs were bad or the coils were shot or the compression was bad I would see issues throughout the range of the engine, but its only when I am below 1500 RPM. I would be happy to hear an explanation as to why that is bad thinking though lol

 

Is the PCM adding fuel? Have you tried running it with the O2 sensors unplugged? What does the PCM think engine temp is?

 

I am not 100% certain what you mean by "is the PCM adding fuel", but I do believe the fuel trims indicate that it is adding that % fuel to the mix, as in its adding 30% at the moment according to that. The engine temp was ~200F and I have not tried unplugging the o2 sensors. That would put it into the limp mode, right? which would be richening up the mixture like it currently is?

Another thing to add is that when the engine is not hot yet it will not have any problems idling, if I drive it for 10 mins it will idle fine (though the fuel trims are still high) but after my 45 min commute to work the idle will get worse and you can feel it shudder.

Thanks for the input.

 

I also put a vacuum gage on it and it did vibrate but it was very slight.

 

Fuel trims are either plus or minus. (adding or subtracting fuel) If they are adding fuel, then the PCM thinks the engine is running lean, for whatever reason. The only reason it would think that, is if the O2 sensors were telling it that.... With them unplugged, it removes them from the equation, and the engine just runs off of tables. (so much fuel for X conditions.) They DO tend to run the engine a bit richer, but, likely be closer than what you are running now. (also, it WILL set codes for the sensors.)

If your truck has a bunch of miles on it, may not hurt to simply replace the pre-cat O2 sensors..... they DO wear out, and then start to react slow, or not at all, under certain conditions. (like, maybe at idle, if the heaters aren't able to keep them hot enough to continue to function properly)

 

So yeah, it is adding fuel.

I will try unplugging them. What should I be looking for when I unplug them? Is a certain result going to determine that they do need to be replaced?