OK... I have a tuff one here. About a month ago my truck started running rough and my gas mileage went directly into the crapper (normally 16-17 miles per gallon is down to 9-11 mpg). I have stalled out a few times and twice the vehicle would not stay running long enough to put it in gear to drive. The roughness is felt at low rpm and at idle.
I checked the error codes and these are what is currently on there (in the order they are displayed):
P0203
P0204
P0205
P0174
P0159
P0442
P0455
Also, the check engine light starts to blink when the P0174 is displayed and it ends at the end of the list. The light blinked 12 times.


The very first time I felt the roughness at idle was shortly after a large and long rain. I thought maybe a short, broken wire etc, but even after a long stretch of no moisture the symptoms have not changed.
I completed a tune-up (plugs, wires, pcv, cap and rotor and ran two tanks of fuel with fuel injector cleaner). After the tune up the only code of P0303 came up. I disconnected the battery (for other reasons, not as an attempt to clear the code) and then the code of P0301 came up. Followed by the 0442 & 0455. A couple weeks ago, I again disconnected the battery and now the above list is displayed. It has stayed consistent for the past two weeks.


Any help would be HIGHLY appreciated.


My vehicle:
2002 Dodge Dakota SXT, 6 cyl, 3.9 standard cab, automatic trans. approx. 135 k miles.

 

P0203 Injector #3 control circuit
P0204 Injector #4 control circuit
P0205 Injector #5 control circuit
P0174 2/1 Fuel System Lean
P0159 2/2 O2 sensor slow response
P0442 Evap Leak Monitor Medium Leak Detected
P0455 Evap Leak Monitor Large Leak Detected

These are the other two codes you had:

P0301 Cylinder #1 misfire
P0303 Cylinder #3 misfire

I'd start by checking all electrical harnesses under the hood and all the grounds. You may want to get a "noid" light and check the injectors. It's unlikely that so many would fail at once, short of a harness problem. You could try swapping them around to see if the problem follows. Check the fuel pressure to rule that out as a cause.

For the EVAP problems start checking for cracks in all the vacuum lines and your gas cap/filler neck.

The O2 sensor codes may be related to the injectors problems.

 

I agree that it is slim that they would all fail at once. I am just lost on where to start. I did not see any obvious problems with the wires but of course that is not saying there isn't one.

The leaks... I have been taping and replacing vacuum hoses as I find them.. the little cracks and dry rot seem to be never ending.

I have to find someone with a gauge to check fuel pressure.
Where would be the suggested place to start looking for wire trouble?

 

Advance or Autozone should have a fuel pressure gauge to rent.

I'd start at the PCM. Pull the connectors, make sure they're clean. After that, start following the harness. Maybe a rodent did some chewing.

 

I would start looking at the PCM connections for moisture inside the connectors. Does your engine have a power steering switch at the pump or pressure hose? If it does, is the switch leaking? Also are you loosing coolant, because if you are that maybe the reason for the misfire on #1 and #3 cylinders. I would also check the compression and perform a running compression test too. I'm guessing with that much mileage, you maybe ready to replace both cylinder heads, with reman's.

 

Quick check of wires show no breaks or burns. The PCM plugs all look to be clean, dry and corrosion free. The power steering pump has two hard pipes coming from it with no electrical connections. And ... it does not appear to be leaking coolant.

I am trying to find wire diagram so I can ohm some wires and do a more thorough review.
Any other ideas... tests... checks.. etc anyone can think of?

 

I really hate to say this, but I hope your PCM is not on it's way out….

 

We had a problem with cylinder heads on all 3.9,5.2 and 5.9 engines with over 75k and what we found, was a hairline crack between the valves on the cylinders that were misfiring.

 

yep and there's a TSB on it I think, it's definitely a known issue. But it takes damn near a microscope to find the crack as I recall.

 

With everything to go at once. . . This was my first thought.. This or mass flow.