Pickup truck help

[The Krypt Keeper]

Normal site I visit for stuff about my truck is down for them to install new upgrades. So since we have such a well diversed group here I am sure someone has some info.

99' Ford Ranger V6 4.0l engine 4x4

manual trans

History

131k miles on the clock use to be a daily driver, now mostly used for hauling trash, hunting, and snow days. So she might see 3k miles a yr now. I do run Seafoam every 1k miles or so as she sits alot more now. But I try to at least drive it once a week to the store, friends house, or to the dump.

Only mods are K&N filter, Flowmaster dual exhaust, 3 inch body lift, 33" tires, and a Jet power chip.

All mods have been on the truck for over 10 yrs. Cleaning of air filter done when needed, and exhaust redone 2 yrs ago but still Flowmaster duals.

Only thing recently done to the truck was I installed a new thermostat a few months ago and also flushed the radiator system and added new.

Symptoms When I go to start the truck it will fire right up however will run rough likes its missing for a few seconds or if its really cold out it will do this for over a minute. After that little rough idle she smoothes out and runs like normal. Also I have noticed my fuel mileage has dropped from 19mpg down to 15mpg. The first time the truck acted up was the same afternoon I went to do the thermostat. Lasted about 15 seconds and smoothed on out, I pulled around back and swapped out the thermostat and flushed the system. When done, I started the truck and it did the same thing for only a few seconds and then back to normal.

Thought about maybe trying some throttle body spray thats O2 sensor safe, maybe even taking the Jet chip out and resetting the computer.

Thanks for any help or info..

Dave

[jon haney]

I was going to say intake leak or vacuum leak, but that shouldn't make you mpg go down that much. Of course that is assuming your symptoms are from the same cause. First I would check for any fault codes in the OBD-II computer. See if that will give you any direction. When is the last time you replaced the spark plugs? My '96 4.0 had the platinum electrodes half melted down after only 60K.

[97xxca]

If you have not done so already, replace the spark plugs and the wires because they do break down over time. Also make sure the intake hose is fully seated at both ends.

Give the fuel injectors a good flush clean along with the intake and Trottle body.

[vetteman]

Air idle control motor?

[The Krypt Keeper]

Plugs were replaced 60k miles ago. Swapping in some new plugs and wires won't be a problem, well at least wont be after all this snow quits falling. Already told the wife I wanted to do it again when I change my oil in the next coming weekend.

Will check both ends of the air intake and make sure its all nice and snug.

Will look to see about pulling the codes also.

Vettman I was wondering about that, however I have never played around with one.

Thats for the help guys. Will see about pulling codes and getting new plugs and wires on it. Hope the weather allows me to do so.

[Mekanix]

This is going to sound all in left field but... fuel pump?

Ford pumps don't tend to go out all at once. They hang on for a while but the pressure is just not up there. Also, fuel pressure regulator may be not holding enough pressure. Without enough pressure, you aren't getting good atomization and it will stumble and lots of poorly burned fuel will affect your mileage. Mostly not about the mileage, but about the stumbling, though.

Also, just as an aside, I would strongly recommend changing out your K&N filter for a standard paper one. I know you get more performance (2-5 hp?), but I have seen from the Hummer H1 website and an engineer here in town that works on Ford flathead showing data that suggests those "high flow" filters are definitely not "high filter" filters. Apparently, somewhere around a pound of dirt over 20K miles flows thru them? I don't have the book in front of me, I'm at work.

http://www.rubberduck4x4.com/ has some article in there, but I don't have time to find it. Apparently they were doing oil testing and found silicates in the oil (sand) and when they went back to a paper filter, the silicates were no longer found. Not a big fan of sand in my engine, but that's just me. Also, paper filters are mil-spec and K&N aren't.

[79cbxmike]

Air idle control motor?

Dodge Ram 3500 -- same symptoms, cleaned up the air idle control motor, no fault code, that fixed it, easy to do.

Good luck

[The Krypt Keeper]

Ok will add a paper filter to the list to swap out really fast also. will look into getting a pressure reading on the fuel system. If its below spec no prob, changed many in the past always fun.

How do you clean the air idle motor? Take it off and clean or some throttle body spray help do it for you?

[The Krypt Keeper]

I had to do some searching on the net and found out how to clean the idle air motor. Pretty simple to get to (2) 10mm bolts and disconnect the harness. Use a electral cleaner and flush it out let it dry completly and reinstall. If that doesn't help Napa has them for around $50 Need to disconnet the battery and let the computer clear and relearn values with the IAC cleaned up.

Filled my truck up again yesterday and average 15.6 mpg all highway. Really suck driving to work as its 94 miles round trip.

So looks like this weekend I will be wrenching away in the snow.

oil/filter

air filter

plugs/wires

clean IAC or replace

See about fuel pressure

Thanks for the help guys.

[cbrxxquad]

+1 IAT, and don't forget to clean the seat. Carb cleaner is what I use.

[XXNUTZ]

Just curious, you mentioned a K & N filter and you clean it on a regular basis...does that include oiling the filter?? If so, how much oil have you been using?? Recommended amount?? In my experience I have found that people over oil the filter and not even know it...what happens then is that the oil gets pulled by the intake vacuum and onto the Mass Air Flow sensor, this can cause your rough running and MPG issues...you can take the sensor out of the housing, it has tamper proof type torx screws, but you can buy them just about anywhere and clean the wires carefully with rubbing alcohol on a Q Tip only...clean out your intake and IAT too, carbon build up is another common issue...unhook the positive battery cable to reset the ECM...when you pull your plugs and they look white in color, then you know you are running lean, a dirty MAF can do this...hope this helps a little, good luck...cheers.

[The Krypt Keeper]

When doing the K&N filter I would clean it and let dry and then spray the oil in a light even coat. Sorta like the first coat you apply when spray paint something.

Will also see about cleaning up the mass air flow sensor with some alcohol.