The 4.0 is pretty cheap used. Hopefully install was not bad.
Thanks, and new! My disregard for changing the one I had is what got me into this situation. So I made sure this one had a new one installed, and my mechanic made it crystal clear to me I wanted it too!
You may be conflating my responses with the questions asked. Might want to look at all again.
I am with OK4450 , i really don’t understand what has been done. Jumping around the thread it seems that a timing belt broke and ruined the original engine. Now one has been installed that might have been rebuilt or is used and has 13000 miles on it . All I do know is the complaint is lower mpg which may not be changed by any suggestions over the web. If the mpg is that big of a concern then Hyper Mileing or trading vehicles might be the only answer.
Also MLC your answers are seen by everyone so you do not need to reply to each person .
I re-read all of your comments and still stand by my questions. You keep describing this as a "new"engine when it is nowhere near new. Going by your last comment it’s well used engine with 130k miles on it. That engine may be worn out; who knows. Many engines with 1/4 of that mileage end up junk.
For what it’s worth, a timing belt breaking on an interference fit engine does NOT mean the engine is destroyed and needs to be replaced. It simply means remove the heads and repair them or replace the heads only.
Over the years I’ve repaired a number of cylinder heads on interference fit engines and have yet to see a “destroyed” engine because of a broken timing belt. Nicked pistons is it and that is not a problem as long as any sharp edges on the nicks are smoothed out.
The operating parameters were learned by the time you reached home with your vehicle, it does not take long.
How many tanks of fuel had you used since the engine was replaced?
The only reference to “new” engine is in the title. I later reference the newer engine as “newer”. Again, where you may have misunderstood was my response to Cavell who asked about the timing belt on the newer engine. In that reply to him, I stated it (the timing belt) is new. Hopefully, this clears up your doubt.
The “complaint”, actually question is, why has the mpg dropped by 25% with the installation of a new[er] engine, when all else remains the same. As for my individual responses, each of you have taken the time to reply and attempt to assist me. The least I can do is acknowledge that time with a reply. It’s the polite thing to do.
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Granted the engine is new to the car and has a new timing belt but that does not mean the engine is in good condition. An engine with say 140 pounds of compression is going to suffer in comparison to one with a more normal 190 pounds.
I’m very leery of salvage yard units because from past experience I’ve seen that a near mid double digit percentage of them have issues and quite often major ones. Some have been outright scrap metal.
It would seem to me if the mileage has dropped by 25% one should smell it at the tailpipe and the CEL should be illuminated.
Just curious, but how are you figuring mileage? Dashboard display? Fill and divide miles driven by gallons?
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Yes, fill and divide miles driven by gallon.
I can’t answer with complete certainty but it has been several.
What fuel economy are you seeing? The Pacifica is a heavy vehicle, the first few years it came with a 3.5 L engine but seemed to be under powered so the 3.8 and 4.0L engines were added. With the 4.0 L engine AWD the Pacifica is rated at 14 MPG city.
Yes, you’re correct however, I’m getting roughly 15mpg combined with this newer engine whereas I was getting roughly 20mpg. On a couple of occasions, strictly highway with a/c off (wintertime), I would get 23mpg!
Without car in hand I can only relate what I would do along with one other comment.
The comment is that I would hope the timing belt is installed correctly and not a tooth or two off.
With car in hand I would connect a vacuum gauge just to verify that things are mechanically sound. It’s quick, easy, and cheap to do if you have to pay for it. That would show a problem with either the belt timing or a worn engine seeing as how it has 130k miles on it.
Vacuum reading on an engine in good condition should show around 19 to 21 inches with a rock steady needle. Down in the 15 to 16 range means a problem which needs to be investigated further.
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Sometimes things just happen, all the engine tolerances are just right. I had a 3.8 Thunderbird that got an unbelievable 35MPG (most of our driving was highway). It was totaled, replace with identical Thunderbird, except for color, that one got 25 MPG.
Sometimes the sun’s reflection off of darker colors can cause aerodynamic drag creating an increase in friction fluidity resulting in decreased mpg. (just kidding 
)
That’s it! First one was dark red, second one was boring metallic grey.
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Excessive carbon build up in the engine can increase the compression ratio, which increases the power output of the engine given the same fuel consumption (greater efficiency). When gets a lot of build up it can ping at full throttle so you should use premium gasoline!
Other than that check that the oxygen sensors are good and making it run with the correct mixture, and that the timing advance is correct. Sometimes a faulty knock sensor or such can cause the timing advance to be disabled which causes a huge drop in performance while using the same amount of fuel.
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Thank you! I use mid level 89/91 fuel now but will try 93 for the next 2 to 3 fill-ups.
But that advice was for your old engine which may have been filled with carbon. As an engine gets older the fuel economy can get a little better due to this. But I doubt it can get worse or better to the point that you are saying. Using premium WILL NOT increase your miles per gallon unless it’s to the point where the lower grade gasoline is causing knocking or pinging and the timing has been delayed due to that. Using lower grade fuel in a performance engine that is supposed to take 91 octane will either cause engine damage or reduced fuel economy at high loads as the computer stops the timing advace.
In your case I suggested checking that the mixture is correct and the ignition timing is advancing properly. A disabled timing advance due to a faulty knock sensor will cause the reduction in economy that you describe. Also, incorrectly set valve timing, such as from an incorrectly installed timing belt can cause the situation that you describe.