2002 Dodge Grand Caravan Sport drop in Fuel economy

I have a 2002 Dodge Grand Caravan that recently dropped in fuel economy by 7 mpg with no check engine light showing. Doing a key on, the check engine light does come on so I know that it is working. I have changed the spark plugs and wires on the van to see if it would help, but has not. The van has 67000 miles on it.

I have also tried running fuel injector cleaner through the system as well as Cat-a-clean from Advanced Auto parts to see if it was a dirty O/2 Sensor or partially clogged Catalytic Converter.

This car uses a MAP sensor, and I have tried cleaning it along with spraying throttle body cleaner into the intake.

The air filter is clean and was put in the van back in May.

The issue started a couple of weeks ago after a fill up, I would have thought that the possible bad gas would have been out of the system by now since I have run the van down to almost nothing left in the fuel tank a couple of times.

I am thinking that it is a sensor possibly out of calibration, but do not know for sure since I do not have a scan tool that shows me what the van is doing actively while the van is running.

Any thoughts as to what could be the cause of the issue?



Sounds like a lazy O2 sensor. You can buy a blue tooth scanner that reads out data to a smart phone cheap. Or you can remove them and heat them with a propane torch and read the voltage output with a voltmeter. They are able to produce their voltage when heated. A lazy one will produce less volts than a good one


Which O2 sensor though, the van has 2 of them, the upstream one or the downstream one? Do you have a recommendation as 2 which scanner to buy that works with the smart phone? Thanks for the reply.


When someone comes to me with a complaint of a sudden drop in fuel mileage, the first two things I check are if the thermostat is stuck open, or if the coolant temp sensor for the computer is faulty.

If the thermostat is stuck open, the engine doesn’t get up to full operating temperature. When this happens the computer stays in the open loop mode. So the computer thinks the engine is still cold and adds more fuel.

If the coolant temp sensor for the computer has failed where it’s telling the computer the engine hasn’t reached operating temperature when it actually does, again the computer thinks the engine is cold and stays in the open loop mode and the computer adds more fuel.


Thanks for the feed back Tester. From the gauge on the dash, it appears to reach temp, so I would thing that the thermostat is working properly, but will need to see about testing to see if the temp sensor is working properly.


Those conditions will trigger a check engine light. Most complains are due to high expectations.

One Grand Caravan customer complained of poor fuel economy without explanation. I asked the service writer for details because a 4400# box will not get excellent fuel economy. The owner claimed in the past he could drive from Las Vegas to San Diego (350 miles) and arrive with half a tank. Nothing can be done to satisfy the customer in some cases.

In my environment a 3.3L or 3.8L Grand Caravan will achieve 13 MPG in the city, 25 MPG on the highway. If you are getting 6 MPG you have a problem but a 7 MPG change from one driving condition to the next may be normal.

I always check the tire pressure first when a drop in fuel mileage is encountered. For me…it usually is the culprit. The thermostat and the coolant temp sensor is checked next if the tire pressure is OK.

I had a 2002 Chrysler T & C with a 3.3. I got 15 city 25 highway (if I kept the speed down to 72). I had a 1992 3.0 Plymouth van that dropped its mileage from 20-22 to 12-14 on a cross country 8700 mile trip. The O2 sensor tripped the light right after I got home and mileage went back up as soon as I replaced the sensor.

To Nevada, the comparison is based on driving at highway speeds, not city driving, Please do not make assumptions as to what is going on, but ask. Before the drop in economy, I was still averaging around 18-20 in the city with the van.

Missileman, thanks for the suggestion, I had already checked the tire pressures and made sure that they were at the proper pressure and checked, very little change.