Thanks for the good data, DSD. I'll be curious to find out what kind of mix you're actually getting. I've been getting 18+ mpg out of the stock injectors, and wondering what kind of improvement I'd get with a more modern design.

very interested in this thread and the topic as a whole. I swear about a couple years ago i was getting 17.5-19.5 in my stock jeep now for about the last maybe year it is now down to about 14.5. I am pretty regular about maintenance I use synthetic oil. I am going on about 60k now since last tune up so I am thinking i should do a cap rotor etc etc... Since I have been reading about the injector swaps definitely considering trying it. Don't want to hijack the thread but let me know what you guys think.
Thanks,
Lee

my 98 5 spppeed abou5 19 mpg.im seriouly thinking its the auto ttrans that is killing my gas mileage.

I know that is part of it but being that I was getting better gas mileage i have to assume there are some other factors involved. I did recently clean my whole throttle body out in hopes that would help a little and seems to have stayed the same... I would be so happy even getting close to 16 in the city. I drive pretty easy 99% of the time.
Thanks,
lee

It depends on how completely you are burning the fuel. Many things can make your MPG worse (rolling resistance, poor breathing engine, lead footitis,...) but proper A/F mixture can have a huge impact.

Lee, Maintenance is very important. My O2 sensor died and I dropped 2 MPG and the exhaust smelled like fuel. Catch up on the basic maintenance, establish a good baseline mileage (how many gallons to drive 1000 miles), and see where you are at.

Alex, Yeah the auto is hurting it some (~5%) unless it is slipping, but the 31" tires and 3" lift are hurting you more. Have you re-geared your rear end or changed your spedometer/odometer to correct for the >10% increase in tire diameter? Your mileage may be 10% more than you think.

I have seen a lot of posts about running Seafoam through the throttle body. Is there an issue with throttle bodies clogging up on Jeeps? I thought that it is only filtered air running through it. There is no Mass Air Flow sensor to get dirty. Really, how much difference is the Seafaom making?

Thanks, David

I corrected the speedo gear.

Im going to try swapping a few parts around from my 98 to my 97 to see if I can't get better mileage. If I can't im going to swap the 5 speed from the 98 into the 97.

Yes actually last month or so I have been getting the o2 check engine light but it hasn't come on in a week or so... I am thinking about checking the ground as they were changed about 60k ago or so. I do keep up on all my maintenance. I go by whatever my uncle says and he is one of the best mechanics around imo. How often do you tune up your xj? I will definitely keep working at it to see if I can get it to improve at least slightly.
Thanks for your input,
Lee

Lee, I have heard that the O2 sensors are only good for 60k miles. Like injectors, some last longer and some less. I changed mine out about 5k miles ago.

It is great that you have a family member that you can trust to guide and help you with your car. My dad does all his own maintenance and taught me most of what I know. We both have restored classics (his '70 240Z and my '72 Chevelle convertable) and still bounce questions and ideas off each other every couple of weeks. Thanks dad!

I have had my Cherokee for 4+ years and have put less than 40k miles on it since I have a few other vehicles to drive. I change the oil and filter every 5k miles and do all of the other fluids every 2 years even though I do not go "swimming" with it in mud holes. Air filter, plugs, wires, cap and rotor at regular intervals. I have never run seafoam through it although I do spray some water down the throttle body every year or so to loosen up carbon in the head.

I love this forum and am constantly impressed by the support that comes from the members here. Thank you to those who help the rest of us get smarter.

David

Not much of a update but I haven't been driving the Jeep much. Unfortunately it looks like the gas mileage hasn't changed.

So more power and better throttle response, with no change in MPG?

That's not a bad thing.

But it'll still be interesting to see how it shapes up once the engine controller has fully adapted.

Id say the same throttle response and power as 703's and the jury is still out on mpg.

Filled up yesterday and did the math. So far im getting the same results as I did with the 703's.

Sounds about right. The 703s have a four hole orifice plate as well, so the fuel atomization should be about the same as the 021s. The 021s will meter the fuel in smaller increments on the low end resulting in beter A/F ratios at idle speed. Since mine runs so smoothly at low RPMs, I may try dropping my idle speed lower.

It would be nice if we could figure out what cc these injectors are and stock. Im really dissapointed in my jeeps fuel mileage.

I tested two stock injectors from mine along with twelve 703s and a few 021s. I tested both static (wide open) and dynamic (short pulses) on a test bench at work. 703s are 10% higher static and 50% higher dynamic than stock. The 021s are 3% higher static and 20% dynamic than stock.