LittleFoot89

I'm getting terrible gas mileage in my 89 4.0 auto. exhaust smells really gassy and sometimes when letting off the gas for a stop RPMs drop so low my lights dim. Came real close to dyin a couple times. Someone told me the choke needed adjustment. I'm a bit of a newbie to the mechanical aspect of a jeep, I'm used to old fords

Any ideas?

highmileage

Welcome to the forum......No choke on the 4.0 but you do have a MAP sensor on the firewall dead center, check the vac line going to it and that it's hooked up. The vac line CANNOT leak. The TPS can cause similar symptoms, but it sounds like your MAP.

LittleFoot89

All the vac lines are hooked up right, I've been having more frequent problems with it stalling out when I let off the gas at intersections and such. Also theres a big black spot of soot on the pavement where my exhaust hits just from starting it in the morning.

I drive almost 45 miles round trip to work everyday and am on a serious budget.
If its not the MAP sensor what else could it be?

buddyantunez1

I would check fuel pressure on the scrader valve before buying any expensive sensors. Thought I had a MAP or TPS issue and ended up being a bad fuel pump.

LittleFoot89

With a bad fuel pump did you experience the same issues I have? Gassy exhaust, temporary loss of power while driving, stalling at stops and bad gas mileage?

buddyantunez1

Yepp, i also had to prime the ignition sometimes for it to start. It would suddenly lose power in the trails or on the street and lurch. It's a quick test to make sure your fuel system is or isnt the problem.

LittleFoot89

Went to re check the vacuum line to the MAP sensor the other day just to be safe, ended up severing the line clean just with a little pressure to disconnect it. I went and got a small piece of rubber tubing to replace that section and the things been running great the last few days. Sounds and feels smoother and hasn't lagged or lurched at all. Mileage is lookin way better too

Lets hope all it needed was that 53 cent fix

cruiser54

Isn't that what was suggested in Post #2? Simple fixes are the best. Congratulations.