I have a 2001 Jeep Cherokee sport with the 4 liter engine with 83,000 miles. It has an interesting problem with mileage. At highway speeds my mileage is a respectable 23 mpg but at city speeds my mileage drops to 7 mpg. It runs beautiful, idles fine, no check engine light. I’ve replaced the air filter, I pulled and inspected the plugs they all looked good and uniform, the gap was good. Oil use is about 3,500 miles to the quart.
I thought before I brought it to the dealer and paid to $70 to do a diagnostic and have them tell me there was nothing wrong I’d see if anyone had any thoughts on this.
Thanks
What mileage did it used to get in the city? Also, I’d take it to autozone first to do a scan for any codes - usually free.
Depending on the type of city driving that you do, I’m not necessarily surprised at 7 MPG. If you go from stoplight to stoplight, idling and accelerating a lot (especially with a rather heavy vehicle), that can use a lot of gas in a hurry. And if you travel short distances (when the engine is cold), you’re running richer than normal anyhow.
A diagnostic probably wouldn’t find any problem, unless your check engine light is on.
I guess I’d have to know how you define “city speeds” to know whether I’d be concerned about 7 MPG.
One possibility is that you have poor injector performance - some people have success with bottles of miracle juice, but if it were my car I would bring it to a specialist who can remove the injectors and clean them on a flow bench.
Also make sure that your shifter is not in D2, where you aren’t downshifting to 1st when you need to - starting in 2nd gear will use more fuel than starting in 1st.
The other thing to check is how you are calculating MPG - ideally you should average a few tankfulls before you know you have a problem.
If you are getting 23 on the highway and have no idle issues, I doubt it is an engine problem. You should be able to get 15-17 mpg in town with this engine. I had no problems averaging above 15 mpg with a 2000 Wrangler (same engine) and easiley get better than 15mpg with my 1998 Grand Cherokee (same engine). But, if I push things hard, I can kill that mileage real easily.
Of course, city driving means different things to different people. If you spend most of the time idling, you will get terrible mileage (even with a fuel efficient car). Also, if you are heavy in the gas every time you start from a stop, you will see poor mileage.
Thanks for the great advice. I finally brought it to the dealer paid the $50 to check the computer codes, nothing, everything checked out fine. My wife only drives 3 miles from the house to work everyday averaging 30 mph, so the engine really never warms up, I suspect this is the reason for the low mileage until we get out on the highway.
3 mile trips will also lead to short battery life. You should get a battery charger and charge the battery for a couple of hours once a month when you don’t go on any long trips.