2.5L ('98-'01) Intermittent throttle. Can't drive it....Issue now rectified.

[DCman]

Hi guys,

So I own this '98 XL with 2.5 and 5-speed.
She's been a good runner since I snagged it in 2012, but last spring, I went to start it up and it idles fine, but when you give it the gas she usually dies.
If I mash the pedal to the floor, she'll keep running, but then all I get out of the engine is it revs up a little, then dies, then revs up, then dies, over and over for as long as I have the pedal floored.
If its not on the floor, it just dies.
If I don't touch the gas pedal, it idles just fine.
I picked up a reader and tried to pull some codes, but it says there aren't any.
I used to work as a mechanic, so I'm not unfamiliar with working under the hood, but that was a long time ago and most of what I'm looking at here is rather foreign to me.
Its been parked since it started acting up and since my dad died, working on cars just doesn't thrill me that much anymore (my dad was a mechanic for most of his life and I learned most of what I know from him)....but this is a "have to", so I'm gonna hafta get it fixed.

So what's going on here?
Bad TPS?
Thanks for any help you guys can provide.

 

[franklin2]

If you are below a certain rpm, and floor the throttle, it will put the computer into "clear flooded engine" mode and turn off the injectors. As long as it revs up high enough, that won't happen.

I am surprised you are not getting any codes. It sure does sound like a bad mass air sensor. Guy in the book says next time you get it idling, tap directly on the MAF sensor, and if the idle drops, replace it.

 

[DCman]

THANK YOU!
I will try that.
Would a bad MAF sensor also cause the truck to backfire when pumping the gas pedal, trying to get the engine to run?

 

[franklin2]

Not sure. But it's a very important sensor for the engine to run. As you are messing with it, you might want to pull the codes again just in case anything comes up.

 

[DCman]

Yep, sounds like a plan.
I will update this thread after I check that.

 

[Fredness]

If the MAF has failed, it reverts back to a Failed MAF table - it should throw a code and run like normal - but no "Learning".

I'd look at the voltage from the Throttle Position Sensor and make sure it is working and not "dropping out" during its sweep.

 

[Uncle Gump]

Have you verified fuel pressure?

 

[DCman]

No I have not done either.
If I measure at the rail, what should the pressure be?
I will check voltage at the TPS, too.

 

[DCman]

I will update this thread after I check that.

...ok that was weird...

So, I realized that since I started working on the truck again (a couple of days now), I had never let it warm up.
Its been quite a while since it was even started, and it idles just fine, so I decided to just let it idle and warm up then see how things sat.
I let it idle for about 3 hours.
When I went out to check on it, the truck had warmed up nicely. I gave the gas a stab and it died. Started right back up.
I tried partial throttle....it worked!.
I blipped the throttle, it revved up and went back to idle, no protests....
I floored it, and it revved up and stayed there!
I thought, hmph, that's strange. Its acting normal now.
I tried to pull it out of the garage. No problems....I idled it up the driveway, no problem. Loaded 2 full garbage cans in the bed and idled it back down to the garage. No problem.
It was like all it needed to do was.....warm up?
Mind you, I live on a main highway, about 10 miles from everything, so there's never been any "short trips" with this truck.
I went around the front and tapped on the MAF several times, idle didn't change.
I figured I'd try taking down the road and see how it acted.
Mind you, at the time I parked it, I could barely get a 1/2 mile down the road and back again.
This time, it stumbled a little puling out of the driveway, so I pumped the gas a couple of times and then floored it....it took right off. Got it up to 45 with no isssues. Turned around, came home, pulled right down into the garage.
I did notice that upon entering the driveway, the engine died, but I was able to start it back up immediately. Truck didn't even slow down.
Pulled it down and into the garage. Shut it off......scratched my head.
I changed the fuel filter last summer, when I tried working on it (at the time, the internet told me it might have been an IAC issue. R&R'd a new one. It idled a little smoother, but still had all the issues it did before).
Maybe there's some crap in the tank that made it into the fuel line and it plugged up the (essentially) new filter?
I'll change it out again and call it good for the time being.
I appreciate all the responses I got here and thank everyone from the bottom of my heart for their help.
You guys ROCK. You really really do.
That one's a real strange one, but at least it runs again......for now.

 

[Dirtman]

It'll act up again the second you drive it somewhere far...

 

[franklin2]

From your description of how it drove I would not call it good. Usable maybe. Now is the time to experiment. Start it cold and see if it presents the old symptoms again. Let it warm up and see if they mostly go away again. Try to get a pattern going to help you figure it out. And be pulling codes along the way to see if anything pops up. Intermittent problems are hard to find.

 

[tomw]

I suspect sticky injector(s). Running at idle, they don't have to flow much fuel, but when demand rises at higher rpms, they could not react fast enough. Maybe.
Run it more/drive it more, and I bet the more you do, the better it runs. OTOH, an injector that was stuck open would flood the intake, and flooring it would turn off fuel flow... and let it run on what was in the intake. Hmm. That should not last long, so doesn't fit the profile.
tom

 

[franklin2]

If it is clogged or sticky injectors, and the fuel level in the tank is half or below, I would buy a can of sea foam and pour the whole can in it and drive it like that in concentrated form. If you it get it really strong the engine may smoke a little bit, but this stuff really cuts that old ethanol fuel gunk out of the fuel system. You will have to run it about 20-30 minutes, and if it did anything you should notice the difference.

 

[DCman]

From your description of how it drove I would not call it good. Usable maybe. Now is the time to experiment. Start it cold and see if it presents the old symptoms again. Let it warm up and see if they mostly go away again. Try to get a pattern going to help you figure it out. And be pulling codes along the way to see if anything pops up. Intermittent problems are hard to find.

Exactly the notion that hit me around 3:30 this morning, so I did exactly that.
First, still hard to start. Not too surprising considering how long it sat. It did start easier than yesterday and once started, idled just fine.
Stalled a couple of times....like as if the choke was screwed up ( I know, carburetor talk, but its how I relate)....wish I could just bend a rod like on the old Rochester's.
Drove it up the driveway, light throttle worked fine, but it acted like it wanted to stall until I got it moving.
It did stall once, at the top of the driveway, but I got it restarted immediately. Again, idled just fine.
...checked the mail...
Drove it back down and noticed, THE CHECK ENGINE LIGHT WAS ON! IT FINALLY THREW A CODE! HALLELUJAH!!!!

...and I bet most of you guys already know what that code is.....

P0102 - MAF Sensor circuit low.

Apparently a common problem with Rangers.
I've got some TBI cleaner, but that's just Carb Cleaner with different lettering on the can. Its pretty caustic stuff, but will clean anything off of anything.
I have to run into town, so I'll look for some MAF cleaner and try that route first.
In the meantime, I found a link to a YT video (Mass air flow sensor (MAF) testing without dismantling - YouTube ) that shows how to check one without removing it (voltage check), so I'll try watching that, too....then try to figure what the heck I did with my old Voltmeter.

....it never ends.

Wish me luck! =)

P.S. - Franklin2 called it from the start! Give that man a Cheroot!

 

[DCman]

OH-KAY, so to put a period on the end of this sentence.....

Went to the parts store and discovered MAF sensor cleaner and TBI cleaner are the same. I already had TBI cleaner at home, so that's $8.99 I saved right off the bat.
Since I was there, I picked up a new air filter, after realizing its been like 7+ years since I last changed it out.
Opened the air box, changed the filter (the old was NASTY! I mean like there was actual green mold growing on it! Icky Poo!!!), shot down the sensor.
Started on the first lick!....then I realized that was probably due to some residual cleaner in the intake hose.
Ran a little smoother for, maybe, a minute, then right back to square one.
Check engine light never did go out....I didn't even bother checking the code.
Considering the age of the truck and that this is the factory original unit, I side-stepped the voltage check and blamed the failure on age.
Ordered a new MAF sensor (there's a core on those! ) and installed it this morning (of course, I had to wait for the absolute COLDEST day of the entire year to do this in my glorified car port ).
Took it for a test drive.
FIRST...no more check engine light ( ), so that's a good sign.
Was hard to start, cold, but easier than yesterday. Again, not surprised considering how long it sat. Every cold start-up is getting easier, so I'm not too worried about that. It will get back to normal soon enough.
Pulled out of the garage and drove it up the driveway. Sensation of stalling was much less than it had been.
Got it on the highway and she took right off. I saw all of these as positive signs, so I drove it just a little farther down the road than I did last time.
Had to stop for a light both ways. No problems stopping or taking off.
Got home and felt I had fixed my problem.....only issue I noticed was that it ran just a little ragged the whole time it was out on the road.
Since it was cold, I decided to repeat my earlier test of letting it warm up.
I left it running in the garage for about 2 hours, then hit the road again.
Ran much smoother.
I decided to take it all the way into town (about 2 miles away) and drove around there for a bit, then came home.
Truck acted just like normal and I never saw the check engine light even flicker.
At this point, I'm calling this project completed, but will keep a vigilant eye on how things go.

....humorous side-note....when I took off the first time this morning, I heard a loud bang as it got on the highway. I figured I drove through a divit in the shoulder of the road and it didn't too much more about it.
When I got home, I notice the tail gate had dropped open. I tried to close it and it wouldn't close.
It was so cold this morning the rubber gasket the gate seats against wasn't flexible enough to allow the latch to engage!
After a couple of tries, I said screw it and left it down.
When I got back from the second test drive, I slammed the gate shut and this time it shut (it was about 10 degrees warmer by then).
I still need to work on that one of these days, though. Gate's bent so one side locks and the other doesn't.....good excuse to pull out my old Torx set.

Anyway, that ends this saga in the life of my truck, Whitey Ford.
Stay tuned kids, I'm sure there'll be more exciting adventures to come....and sincerely, thanks again to everyone who helped here.
I really do appreciate you guys.