stumbling then suddenly not stumbling

[jamie3529gq]

My 01 5.0L mountaineer was doing some weird stuff yesterday. Left work, it started and ran fine, about 5min in it started stumbling badly, so bad at times I didn't think i'd be able to keep going. then suddenly it would stop stumbling and the truck would take off like a shot. like flipping a light switch. did this off and on all the way up I75 for 20 miles, had to watch i didn't run into the back of someone when it suddenly stopped stumbling and surged forward. then, the problem stopped for 25 miles up M24, ran like a top. Stopped for smokes at a gas station, truck would hardly run again. pulled out and floored it, suddenly HOLY CRAP here it goes - took off again.

Ran codes when I got home. O2 sensor heater failure, fuel trim on bank 2 ( i think - gotta check again) was way negative, -25%, misfire detected cylinder 5, etc etc . I was like armageddon on the code reader.

I just don't understand what would make the issue turn on and off like a lightswitch on my way home. I am thinking a bad wire somewhere? Any thoughts before I start replacing stuff?

Thanks!

 

[MAS Tequila]

Have you changed the fuel filter?

MT

 

[jamie3529gq]

Have you changed the fuel filter?

MT

Oddly enough, just last weekend i changed it.

 

[jamie3529gq]

Also last weekend I replaced my rear bumper,it was bent down badly from a rear ender. I had to beat on the frame rails pretty hard to straighten them. I don't imagine any connection to this problem, but who knows??

 

[jamie3529gq]

more info. codes P0155, P1151, P1152 and P0305

started it up this morning, it looks like bank 2 sensor 1 is stuck at around .465V, doesn't vary more than .01-.02 volts. bank 1 sensor 1 runs from 0.1 to .75 volts.

Short term fuel trim bank 2 sensor 1 was sticking around -23 to -25%. Truck was chugging nicely at idle, engine vibrating quite a bit, you could spill your coffee.

It all points to bank 2 sensor 1 oxy sensor, but i don't understand the 'on/off' characteristic of the problem yesterday.

 

[Lefty2053]

Hope it isn't an open injector like mine. The intake has to come off. I have the same systems and I know it is injector 4. A bad wire that sometimes gets good connection could be both our problems. Either way intake has to come off.

 

[jamie3529gq]

i replaced the driver's side O2 sensor, prior to the cat, seems to have fixed the issue. Motor is smooth as butter again, and the fuel trim bank 2 is back around zero. Only drove about 5 miles though, idled a long time, no check engine light, no stumbling. Here's hoping....

Still don't understand the intermittent deal, but whatever, it seems fixed.

 

[jamie3529gq]

Update on this one. Truck sat for 2-3 months (mama wouldn't let me have insurance on my Ranger and my Mountaineer at the same time) but I recently re-insured it to get it ready to pull my 4 wheeler on a trailer up north. (next week, can't wait)

First off, the first day I drove it again (after changing all the rear diff bearings) the alternator failed, I almost made it back home.... anyway, that's a side story.

After fixing the alternator issue, the next day it did some random 'stumbles' again, short duration, motor shakes like an SOB. Then like a light switch, smooth again. No error codes, but I had the code reader on my phone while driving to work the following day so I could watch the fuel trim if it happened again. Only 10 seconds it happened, but I caught bank 2 fuel trim drop way negative while it was stumbling.

I remembered when I changed the O2 sensor that there was a lot of oil around the connector, so I got under the truck, disconnected the sensor and sprayed the whole thing out with brake clean. Put a bunch of dielectric grease on the pins, and reconnected the sensor. I swear the truck is now running and idling smoother than it has in the two years I've owned it.

Probably should fix that oil leak someday...