My 2000 T&C with 3.8 just turned 100,000 miles. My gas mileage recently dropped to about 11-12 mpg. My wife drives it so I can't say if it dropped quickly or gradually. I have a new fuel filter I bought a while ago and am wondering if that could be the cause. It runs perfectly and no engine codes. I bought it with 83,000 mileslast Sept and have repair records. The fuel system was cleaned with new plugs and wires at 55,000 miles. Stock oxygen sensors as far as I know. New air filter. Thanks.

 

what plugs did u put in?

 

Not sure. The previous owner had them done at 55,000 miles. I bought it with 83,000 miles and the mileage has just recently dropped.

 

Do you think the engine RPMs are still about the same when you get up to speed, say 60 MPH? You should also be able to see the RPMs drop as you pass through the various shift points. What was the mileage before it dropped?

 

Also had another thought, if you have not changed the O2 sensors yet, might be time to do it. I think they can cause a decrease in mileage before they degrade enough to set a trouble code.

 

no they dont if u drop that much in MPG then u would have a lazy o2 and that would set a code.
If u want to know for sure find some one that has a scan tool that can get into the fuel adaptives and see how high they are.
My first guess and still the one I am sticking with is the plugs. U dont know what tehy had put in if its anything besides champion plat then u will have an issue and should be changed out first of all. Senond look at your throtle body see how dirty it is can clean it out.

 

I had checked the throttle body and it looks clean as a whip. The mileage prior was in the 15-18 range with about 90% in the city and my wife has a lead foot. On the freeway itused toget19-20 mpg. It shifts crisply and I haven't noticed a change in the RPM at any range. I have not changed the O2 sensors and don't know if they are original or not. Changed the fuel filter last night and it was a Mopar filter so I'm guessing it was the original. Ever since we bought it there is a flat spot when hitting the throttle. Feels likethe flat spoton my '56 ****** when I don't get the accelerator pump set perfectly. Is that the TPS?

 

tps is only a sensor if the tsp was an issue with say voltages not reading correctly and the engine load was different u would get a map and tps corrlation code.