'99 4WD Starting Issue and MPG

[aberrant]

My '99 Explorer EB 4.0 has an intermittent staring problem. It starts up fine, but when coming back down to idle RPM, it sometimes drops significantly and then dies. Doesn't happen all the time. I've been giving it a little gas each time after starting which has solved this problem, but would prefer to fix the issue.

Also, I'm averaging 13.4 MPG around town in this truck. Planning to change out the plugs and wires, but anything else I should be looking at? Trans, rear diff, and engine oil were all recently changed. I use Ford Synthetic Blend 5W30 for the motor. Should I switch to something else? I've read that changing the exhaust and modifying the air filter box can help some, but would those mods be worth it?

Thanks.

 

[masospaghetti]

Stalling issue could be the idle air control valve which is fairly common these vehicles. You can try cleaning it first.

Fuel economy isn't going to improve significantly with exhaust and air intake and it definitely not worth it for this reason. Check that your tires are inflated correctly and the brakes aren't dragging. You could try a DIY front air dam to improve aerodynamics, your 99 should have a small one from the factory under the front bumper.

Also make sure you aren't running the A/C if you don't need it, keeping in mind that these Explorers will run the air conditioner on all settings except VENT and FLOOR. The compressor uses a lot of energy and it will impact your fuel economy.

 

[aberrant]

Stalling issue could be the idle air control valve which is fairly common these vehicles. You can try cleaning it first.

Fuel economy isn't going to improve significantly with exhaust and air intake and it definitely not worth it for this reason. Check that your tires are inflated correctly and the brakes aren't dragging. You could try a DIY front air dam to improve aerodynamics, your 99 should have a small one from the factory under the front bumper.

Also make sure you aren't running the A/C if you don't need it, keeping in mind that these Explorers will run the air conditioner on all settings except VENT and FLOOR. The compressor uses a lot of energy and it will impact your fuel economy.

Pretty sure I replaced the IAC valve a couple years ago. Will have to double check and clean if necessary.

Thanks for the tips regarding the fuel economy. I do run the AC and use the Auto function, so will have to cut back on that and see how it goes. Just ordered new spark plug wires, so will be changing those and the plugs soon.