jeepster1958

OK....I know Cherokees or Jeeps in general get lousy gas mileage but I had a 98 Cherokee and it got 15 MPG and that was ok or normal but I got a 2000 and did a injector upgrade and installed a new coil pack and spark plugs and it didn't help at all. I struggle to get 14. I am wondering if I didn't reset the computer right or if I used the wrong spark plugs maybe? I used Autolite Copper plugs. Cheap but I heard a Copper plug was ok. PLEASE... Any ideas?

Kymasabe

Plugs help light the fuel/air mix but often won't have any kind of significant effect on fuel mileage. When you say injector upgrade, what did you do? What size came out and what went in?

jhc7399

What he said ^^ .

Which injectors did you use?

Kymasabe

Regarding your plugs: Everyone's experience is different, but I've never had good luck with Autolite's. I often stick with what the vehicle came with from the factory so the first plug that comes to mind would be a Champion ( I run Champs in my Johnson outboard as well, is the plug it likes best). I have to admit though, I'm a big fan of NGK so that'd be my second choice (or first, depending on the vehicle). I've also heard lots and lots of people having good luck with E3's as well.

'90Cherokee

And I love Autolite/Motorcraft plugs and the only plugs I've had issues with are Champions and the original Bosch platinums.

I generally say to go with OE but have had great results with NGK iridiums as a non-OE option, but haven't tried them in a 4.0 yet.

This could become the equivalent of an oil thread.

Kymasabe

Yes it could, I'm still waiting to hear the story behind the injectors....

'90Cherokee

It would also help to know if the mileage went up or down after the injector swap and whether the rest of your rig is stock or not. Tires & gearing will play with perceived and actual mileage. Other stuff like a roof rack, lift, etc. will also play with mileage.

jeepster1958

Well first of all thanks for the responses...I went from a single hole injector to a 4 hole...not sure what brand....everything is stock....mileage seemed to have dropped after the so called tune up/injector upgrade

Kymasabe

So...no increase in injector size? No change in flow rate? Check engine light on by any chance?

jeepster1958

Well they are suppose to be the same pressure just 4 holes instead of 1 single and the engine light does come on every now and then but it did that before and it doesn't stay on long

Kymasabe

Theres a difference between pressure and flow rate. What are the flow rates of what came out and what went in?

jeepster1958

I bought them off ebay from injectordyne....im 99% sure they are the correct ones. Ive double checked the part number

jeepster1958

I think I may try resetting my computer

jeepster1958

I really don't think its a improper injector problem. After I installed them the Jeep started right up. I think it may be another issue because the engine light was coming on beforehand

jeepster1958

Injectordyne purchase from ebay