2006 Town & Country - MPG drop to 13 - 17 mpg from 19-24! EVAP or Torque Converter?

chrysler
towncountry

#1

I recently purchased a 2006 T&C Limited (3.8L V6) with 58k miles on it… Immediately after purchase, I averaged 18-24mpg… soon after purchase, a shudder occurred b/w 38-40mph and a little later check engine light came on (P0456- small EVAP leak)…

For shudder, I immediately replaced tires, shocks, struts, etc. however, the shudder remained. So, I took it back to the selling dealer who flushed the transmission, yet the shudder remained. After several weeks of diagnostics with the selling dealer, I agreed to split the cost of a torque converter replacement to fix the shudder (it worked)…

For the code, they replaced the EVAP solenoid at time of transmission flush. However, the check engine light came back on (same code) and we noticed our fuel efficiency is now in the 13-15mpg range. After a smoke test and drop of the fuel tank, a crack in roll-over valve was found…

A new tank is on order for replacement (along with a fuel pump while I’m in there). However, I’m looking for direction on if the EVAP leak could cause this significant of a reduction in fuel efficiency, or if the new torque converter is more likely the issue, although the selling/servicing dealer wants nothing to do with it. Any direction is appreciated…


#2

I doubt the loss of mpg is caused by either the new torque converter or the evap leak.

More likely something else like a bad coolant temp sensor, which can cause the engine to run rich and reduce mpg, or a stuck closed thermostat which will have the same result.

You can have this checked by a competent mechanic with an OBD scanner. With the engine hot, have the mechanic do an OBD scan and verify that the engine is running in “closed loop,” which means the coolant temp sensor is working properly and the computer is delivering the correct amount of fuel through the fuel injectors. But if the engine is running “open loop,” that means the computer is delivering extra unnecessary fuel, which it will do if the coolant temp sensor is faulty. And running in open loop will knock several mpg off your mileage.


#3

If you have a crack in your gas tank, that would account for both the P0456 and the drop in fuel economy.


#4

Years ago, a college roommate was complaining about his lousy fuel economy. It turns out he actually had a pinhole in his gas tank. After getting that taken care of, everything was back to “normal” . . . it was a POS Chevette

Later, he got tired of the “car” and sent it off to the boneyard . . . with a full tank of gas. That fuel was probably worth more than the “car” itself

LOL


#5

Unlikely mpg loss is due to evap problem unless liquid gasoline is actually leaking out. In that case, you should be able to see it or at least smell it. You might want to read this link which explains how evap systems work on modern cars. Includes info on “small leak” DTC’s.

http://www.agcoauto.com/content/news/p2_articleid/294

edit: I think a Town and Country is a Chrysler, right? If so, look at article 295 too. Chrysler evap systems work a little differently than other makes.

For the mpg loss, my first suspect would be as mentioned above by jesmed, something to do with the coolant temp or coolant temp sensor. This will likely prove difficult to diagnose for a driveway DIY’er without the proper scan tool equipment and shop manual procedures.


#6

Thanks for the feedback… After reading article 295, I’m wondering if I should just replace the leak detection pump while I am changing the tank out…

I have a local shop that enjoys watching a corporate desk monkey like myself learn to turn a wrench. They’ve been good (aka. fair on pricing) to me when I reach a point of safety, tool or computer constraint.