Help, poor gas mileage...

Hi, I drive a 99 explorer sohc 4.0
Recently it had sat outside for a couple really cold MN days w/o running and when I went to start it would turn over but not start. I had to depress the gas pedal quite a few times to get her going. Ever since it has been fine starting but I've been getting considerably lower gas mileage. I've been told I might have flooded it and possibly got some condensation in my spark plugs.:banghead: If this is true, would the condensation be in the plugs themselves or the wires? I ask because the spark plugs are newer but the wires are not, do you think I can get away w/ just changing the wires or do I need to take the plugs out and dry them out or change em? Does anybody have any advice cuz I really don't know much about this...?

Any help would be greatly appreciated:smooch:

I don't think it would be condensation. I suspect what they meant is the spark plugs were saturated with fuel and therefore it was difficult to get a hot spark. However, after a few miles of driving, that should have remedied itself if everything else was good. It sounds more like you have something causing the truck to run rich. My first suspect would be the Idle Air Control (IAC) which opens and closes the throttle plate (when it works) during idle and starting. I'm not sure that would cause low fuel economy when driving though, unless you're really letting the truck warm up a long time before driving.

How much decrease in fuel economy are you experiencing? What grade fuel are you using, and is it an ethanol based fuel?

You also should check your Coolant Temperature Sensor Onot the sender or the guage in the instrument cluster) and the fuel pressure.

Have you done any modifications to your engine that may have an impact, such as using a K&N air filter, cold air intake, etc?

-Rod

Hey rod thanx for the speedy post!
I do let the truck warm up a bit before running because ever since I've had it, it takes awhile to build enough oil pressure for the warning light to go off if the temp falls down around 0 or below. I typically use this as my warmup time because the colder it is the longer it takes for the light to go off and as soon as I leave I'm usually right on the highway so I don't want to be hard on a cold engine.
Nothing changed though as I'm still warming up the same as before, only before I was still pulling 17-18 mpg, and now I'm getting 13-14. I drive pretty steady routes w/ my truck as well to work and back (HWY) and to daycare and back (CITY). It just seemed to take a nose dive immediately after that morning of not starting right. There is no modifications whatsoever to it, all factory. I also use 87 octane as the manual instructs to and almost all MN gas, other than diesel, runs 10 % ethanol and maybe some that run 5%.
Someone told me I should replace the fuel filter, not sure why it would take a nose dive like that if it was the fuel filter but I know it is really old and should be changed anyways. I'll wait until I hear back from you but I might try the IAC as well as there seems to be lots of people on here having problems w/ that. I have no idea how to check the coolant temp sensor or fuel pressure, do I need to have it looked at by a mechanic ya think?

If you plan to keep this for awhile, I'd suggest you start with the remainder of the tune up, plug wires, fuel filter, air filter, inspect vacuum hoses, and clean the Mass Air Flow (MAF) sensor.

The Coolant Temp Sensor you could check with a ohm-meter if you have the specs for it and know the coolant temperature. Obviously, this would be most easily checked after the vehicle has sat overnight so you can trust the coolant temp is the same as the ambient air temp.

Fuel pressure requires a fuel pressure guage which attachs to the fuel rail at the intake manifold. Often you can pick up the guage for around $10 new at a local auto parts store. At the current price of gas, that could pay for itself quickly. It would be preferred if you could check the fuel pressure before and after replacing the fuel filter to see if it makes a difference. You'll also want to check the Key On, Engine Off (KOEO) fuel pressure as well as the Key On, Engine Running (KOER) pressure.

-Rod

Hey thanx alot for your help, I think I will finish off the tuneup-I've been meaning to do that anyways. If that doesn't work I'll have to have someone help me try those things you suggested. Love this site and now this forum!!