No catalytic convertor and poor fuel economy

foresterdj

foresterdj

Member
Supporting Member
Joined
Mar 25, 2019
Messages
64
Location
MN
I have already read 2 or 3 times the official O2 thread and others dealing with these sensors. I just bought this Jeep in February, the kid who had it previous for only a few months and knew no history on it. One of the 7 previous owners removed the catalytic converter, the exhaust pipe where it should be has a fitting with, I assume, a down stream O2 sensor. Jeep runs fine no check engine light. Have not driven it much in the month since I hauled it home.

I had filled it with gas while still on the trailer. Went for a spin yesterday and filled again. 20.1 miles 3.9 gallons. Do the math, that's barely over 5 mpg.

Speedometer gear was changed by me, reads dead on with gps at 55 mph, so miles should be good.

Did I have it as full the first time? Don't know. Will take a few more tanks to verify, a single 20 mile run not a fair test.

However, O2 threads discuss poor mpg with bad O2 sensors.

Not sure what sensors are in it, but there is no check engine light.

I am inclined to A) put in two new sensors, or B) have a new catalytic and sensors installed.

Likely B. But a nagging question is what may have been done so there is no CEL. It would seem the O2 sensor that was put into the exhaust pipe could not be sending proper signals without a catalytic in front of it.

Let the comments and suggestions begin.
 
The downstream O2 sensor on the cat has nothing to do with performance or mpg. Only the upstream O2 sensor just below your exhaust manifold has any effect on mpg or performance. Also, I just looked at your profile, you may want to correct your 2.4L engine listing to 2.5L. Your '98 came with a 2.5, the 2.4 came along years later.
 
So, would you suggest running a couple tanks to see if mpg really that bad, then if so install new O2 sensor upstream.

What would a sensor in exhaust pipe where catalytic should be accomplish?
 
I would certainly keep careful track of MPG but, truthfully, if it were running that rich I would think it would a) smell like gas and probably be blowing white smoke and, b) run kinda like crap.

Check for fuel leaks from the tank and any of the lines up from the tank to the injectors.

EDIT: Welcome to the forum and cute pup!
 
20 miles up hill? 20 miles with your foot to the floor? It sounds to me like you might be jumping the gun on the mpg. Run the thing for a bit. Especially if it has been sitting for a long time. I have no doubt that my jeep will get mpg that bad now and then. (up hill, into the wind, trying to pass a semi) Run a whole tank so that you can get a good average.
 
  • Like
Reactions: TJ Hunnicutt
Further monitoring of mpg is in order. I'm kind of anal on that and track every tank on every rig I have.

Does check engine light come on when starting? I will watch next start.
 
I have a 2.5 auto with small tires and get 17 mpg. Check full tanks for sure. Short drives can throw things off. 26 miles one way to work for me so a 20 mile drive is fairly short in my world.

Trip length is huge. My wife and i both drove scion xBs. Hers auto mine manual. Her mpg should have been higher based on factory numbers, but her 2 mile commute worked out to 24 mph, my 26 mile freeway stop and go was almost 31.
 
Second trip much better, 14.8 mpg. I am guessing that when I first brought it home I must not have filled it full up.

I checked today and the check engine light does illuminate when starting.

For now will put new O2 sensors on hold.
 
Top Bottom
Back