1995 Jeep Grand Cherokee Town Mileage Dropped 5 Mpg 18 Mpg Highway 20 Check

Look for a fuel leak. The Engine Computer can only modify fuel metering by plus or minus about 10 percent so even if it was getting incorrect information from the map sensor, fuel mileage would only drop by a few miles per gallon. To be getting only five miles per gallon with no leak, you would have to just about have raw fuel dripping from the tail pipe, and there would be a lot of black smoke from the exhaust.

Look under the vehicle for wetness, especially along the right side. Pull the vacuum hose from the fuel pressure regulator to see if it's wet inside. Smell the oil on the dipstick. If it smells of gas, suspect a leaking fuel injector, but that is real uncommon on Chrysler products.