Yep^^^ front one is the one needed. Back one is just to let the pcm know the cat is working.

And zman, that part number is what I've always used. I picked it up on a forum years ago. I think it may be cooler or it was replaced with a new number. Don't know but they work great.

 

dhvaughan,

Honestly I'm not sure which o2 sensor the simm is in place of. I was just assuming it was the front one. When I got the headers, there was only one 02 bung. I had a buddy who happens to be a mechanic install them for me so I would hope that he would know which one needed to be cut off and replaced with the simm and which one goes into the bung on the header. If he got it backwards, would the truck even run?

The plugs look like the top picture in this chart:

http://www.aa1car.com/library/reading_spark_plugs.jpg

I assume they are wearing normally since they look like the "normal" picture, only a little more gray than brown.

The tires are stock size (265/75/16) and the odometer should be fine and it shows just over 115,000. You may have found my problem if the 02 sensors/simm setup is backwards.

 

Bumpity bump

 

The pre-cat (upstream) O2 sensor should be in the passenger side header. The post-cat (downstream) sensor would be a foot or two after the catalytic converter, but long before the muffler.

Yes, the truck would run, but it would run off incorrect sensor data, screwing up your fuel/air ratio, which could very well explain your bad MPGs. These trucks with the 5.9L don't get much better, usually, than what you're getting now, but usually they do get a bit better.

 

Hmm...this issue might be with the location and grade of gas I get.

I took a weekend trip last Friday-Sunday. I filled up with regular 87 octane on Friday and added a can of Seafoam to the tank. When I got to my destination, I filled up and calculated my mileage at just over 14 MPG. This was all interstate between 80-85 MPH.

When I filled up at my destination, I filled it with premium 90+ octane. I drove around for a couple days in a large city so I drove it a little bit harder than I usually do in the small town I live in. IOW, the 1-2 shift occurred at 2500 RPM instead of 2000 RPM because I was driving a bit faster and giving it a bit more gas to stay up with big city traffic.

Anyway, I calculated it again when I got back home and with the big city premium gasoline, I got 17.9 MPG. I'm not sure how much the Seafoam helped but something is definitely weird here. I didn't realize that driving the truck a bit harder would get me better mileage. LOL

EDIT: That sounds a little confusing. I'll simplify it a little bit.

Town A to town B:
Filled up in A with 87 octane and can of Seafoam
Drove between 80-85 MPH to B
Got 14 MPG

Town B back to town A:
Filled up in B with 90+ octane premium
Drove around in B for 2 days then drove back to A
Drove between 80-85 MPH back to A
Got 17.9 MPG

Is gas quality between different cities really that different sometimes?

 

I think The seafoam helped I'm going to get a can this weekend and do it. Who much do you put in and where? Thats a nice improvement.

 

Doesn't surprise me in the least. In really simple terms, gasoline is a blend of two types of molecules ... heptane and octane (7 and 8). Heptane like to burn fast, octane likes to burn slow. The more octane present, the slower the fuel/air mixture burns. This has the same effect of retarding ignition timing. The flame front takes longer to reach the piston top so it's already on the way down by the time the power reaches it ... wasted power, increased heat, reduced mileage. In a properly tuned engine , the flame front will reach the piston top just as it passes TDC so maximum power is transferred to the piston. The spark is supposed to occur slightly before TDC because it takes time for the mixture to burn. If it fires too early, the flame will impact the piston before it's ready to head down and that's where pinging comes from. That is why hightest helps reduce or eliminate pinging.

Using hightest in a truck tuned for regular is a waste of money in two ways ... it costs more to get less.

Any of this make sense?

 

Excellent explanation TMS, And BTW! dodge15004x45.9, are you kidding me with that question ? Not only are the directions on the can, but there have been hundreds of threads about using Seafoam, about how it works and where it goes.

 

Yea I know I'm a young dumb kid( if you can't already tell) and I don't want to go messing stuff up. So I go muddin instead and climbing hill that are so steap that it felt like my front axle was coming off the ground. It was fun I impressed a few people today they think my ram is a pice. They don't think that anymore. My passenger was holding on for dear life and I was laughing my fat happy a$$ of the hole time the kid with me wouldn't do it and he thinks he jeep is tuff $hit. It was a good time thank god for gas line and hill. What a fun 20min hike that was.

 

I think I get it so me putting 89 in instead of 87 I'm pissing my money out the pipe since it is not tuned for 89 is what your telling me.