hoopesjeeps Posted February 23, 2018 Posted February 23, 2018 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! Thanks! Sent from my SM-G955U using Tapatalk
Kyleinreallife Posted February 23, 2018 Posted February 23, 2018 You’re driving a 30 year old brick. We don’t have the luxury of thinking about mpg....just tune everything to run well87' XJ Wagoneer I-6 AW4 NP242
87MJTIM Posted February 24, 2018 Posted February 24, 2018 My MPG dropped and I didn’t know why. I purchased the REM from nickintime on facebook/youtube. i discovered my O2 sensor was busted. I changed it, now the MPG is back up.
DirtyComanche Posted February 24, 2018 Posted February 24, 2018 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.
cruiser54 Posted February 24, 2018 Posted February 24, 2018 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.
Eagle Posted February 24, 2018 Posted February 24, 2018 +1 on checking O2 sensor and MAP sensor. Also, a partially clogged catalytic converter can cause all sorts of issues.
omega_rugal Posted February 25, 2018 Posted February 25, 2018 any black smore coming out the exhaust? does it smell like gasoline? also check for mini leaks in the entire line, a small unoticed leak overtime can lower MPGs too
Eagle Posted February 25, 2018 Posted February 25, 2018 A small exhaust leak (cracked header, or loose header bolt) also results in running rich. It fools the O2 sensor.
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