I would like some suggestions and info for a problem I am having with my 2002 Dodge Dakota 3.9l engine. The problem or issue is with rough idle and other related rough running or stalling issues. The problem is intermittent but does get worse when I use regular gasoline and gets even worse if I use 10% ethanol fuel, if I only use premium fuel the problem almost goes away.

The problem has never caused an engine code or anyway of narrowing down a solution.

So I need suggestions on what to replace or do to fix the problem.
After doing some research on the problem I have narrowed down a few possible solutions but would still like some other opinions.

I have narrowed the problem down to a possible oxygen sensor or something wrong with the computer. I fell the computer is less likely because of the severity of the problem with different fuel types. I have ordered a new oxygen sensor and will be replacing that in a week or two. I ordered the sensor that should be the most likely cause of the problem but until it is installed I won't know how good my guess was.

Any other suggestions on the random rough idle and stalling out of this engine would be great I am stuck and don't know what else the problem might be.

Thanks for any help.

Jared

 

i would think if it was an oxygen sensor then the check engine light would come on

 

Yeah if it is an O2 sensor almost always you will get a code. Maybe something in the fuel system.

 

the o2 sensor is not a bad guess, since they CAN be bad w/o throwing a code, many people have had that problem, gas mileage will also be down if the O2 sensor is bad

but do a full tune up, plugs wires, cap rotor, ect and let us know if that helped

 

when was the last time you change your spark plugs or wires?

 

when you do your tune up, clean the MAF sensor at the same time.
Disconnect the battery for a good 20 minutes and let the computer caps bleed down. The computer will have to relearn your driving conditions so make sure you do not have premium fuel in the truck for the first tank of gas.
If you have high mileage you may have some compression issues, built up carbon will raise the compression and the engine knock sensor will reduce the timing to compensate. Or you could have low compression due to wear and again, computer compensation.
no way to tell until you replace the wearable parts first.
Plugs, wires, cap, rotor, clean MAF, air filter, and spray out the throttle body.

 

I recently changed the plugs I did not do the wires at the time. I saw no reason for it as everything looked to be fine. The truck only has 45,000 miles on it and is in very good shape, so if this change does not work then I will start checking other things and doing tune-ups.

Yeah I thought it could be some fuel system related problem but since there is no fuel filter that can be easily changed and the problem is so intermittent it is very unlikely that it is a fuel pump it kind of eliminates any fuel system problems that I can think of.

This is a problem that has been going on for about 1.5 years already so I have done a lot of research and asking to figure out what the problem is. I get told by mechanics "well when the check engine light comes on bring it in and well take a look" well since that has never happened I am SOL. So far the things I have come across as possible fixes or problems are fuel filter, fuel pump, fuel something, ECM, computer, spark plugs, or other ignition related problems, oxygen sensors and a few other things. So is the oxygen sensor a shot in the dark? yes, but I want to get it fixed and its a lot cheaper than a $400 ECM or a 400-600 pump.

So as I said before I need possible solutions, cause even though I agree that there should be a check engine light or a code, telling me that does not help me.

 

remember that o2 codes do not automatically mean you have a bad o2 sensor, all the time. An o2 code means that you have a rich/lean condition, ( most times) and that could be a sensor, or a problem.
people see 02 codes and without regard, change them out for no reason.
check your wires with an ohm meter to see if they are leaking, sometimes they look good but if you open the hood at night, you can see fireworks all around the GOOD LOOKING wires. better yet, grab onto them and see if they leak!!!! you will know right away, ( don't do this you may have a heart attack)
The BEST thing you can do is start from scratch and do all the tune up yourself. your labor is cheap.
Once you have done it all, move on to the intricate troubleshooting.
Any mechanic you bring it to will do exactly that and charge you for parts (marked up) and their labor before they begin to diagnose it anyway.

 

i used to have a kinda rough idle. it didn't bother me at all and it wasn't interfering with performance or anything. one thing that helped was when i took off my TB and just scrubbed it really clean. other things that helped were when i did my new TB and and a MSD ignition blaster coil. between those 3 things there is a really noticeable difference? also, what plugs are you running? i know some (don't recall off hand but i think its the platinum ones) that these magnum motors don't like.

 

i would do a full-out tune up and run a tanks worth of seafoam or something like that... seafoam can clear up a rough idle to some extent... if that doesn't help, then maybe its the O2 sensor or something along the lines of that... start with the obivious/easy and then move to the bigger more difficult stuff...

Cheers.