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Low MPG Ideas???

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I am averaging 8 city and 12 highway (60 mph) in my 88 4.0 5 Speed. I don't have any sort of a lift. Or anything else that wo uld normally cause low MPG.


Has anyone else experienced this I would love to hit the advertised 21/23 If at all possible!




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1 hour ago, Kyleinreallife said:

You’re driving a 30 year old brick. We don’t have the luxury of thinking about mpg....just tune everything to run well

87' XJ Wagoneer I-6 AW4 NP242


Mine gets around 20-21 normal mixed driving with a lift and 32s or whatever they are.  I reset the tripometer on every tank because I don't trust fuel gauges.


O2 sensor, MAP, and CTS are where I would start, along with the standard tuneup stuff like the plugs and rotor.  Also check your brakes aren't hanging up and you're not stuck in 4wd, although those are both obvious.

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I also would suspect a bad O2 sensor. Supposed to be replaced about every 60,000 miles. Use only NTK23553.


If that tube from your throttle body to MAP sensor is leaking AT ALL, the MAP will tell the ECU you're under heavy load and the ECU will open the injectors for a longer period of time and you'll suck the gas. 



MAP to TB.jpg

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