dombex

Hi,

This may seem like a foolish question but I'm trying to track down my engine skipping/ bucking during slight acceleration on slope.

So,

If I have a slipping tranny, will my RPMs increase slightly as it skips? You know, like as if it was in neutral? Or if was a manual tranny and you depress the clutch slightly, the tranny slips AND the RPMs increase.

Cause if it isn't my tranny, I'm wondering if it's my plugs and coils, they're original; 2008 FX4, 93,000 miles original plugs and coils.

It really skips like the plugs/coils are firing all the time, but only going up a slight incline.

I know it's a confusing situation but I'm on Social Security and I want to fix as much as I can before taking it to the shop. At more than $100 an hour, I'll do what I can.

Thanks in advance,

Jerry

kozal01

iTrader: (2)

Yes, a slipping trans would show a rise in RPM's. What you're experiencing is extremely common though and yes, its almost always related to plugs and/ or coils.

needsmoarturbo

Sounds like misfires.
start with changing the plugs and cleaning the ignition coil springs. Coils rarely go bad. You can replace the rubber boots and springs for about $35 per set of 8.

redfishtd

Oem coils rarely go bad they just corrode and need cleaning . You have classic misfire symptoms . ford changed that 100k mi stuff on plugs its 60k mi now it was a sales gimmick .
Do a full hospital clean plug job with new boots. You should have no liquids getting into plug wells .

Rippedsquad

wrong post here sorry--edited

Jimboy

Go to Autozone or other and get your trouble codes (DTCs) read and report back. You can pin down which cylinder(s) are having the problem and, at least in the short term, concentrate on that and save some time and money not to mention its pretty cold out right now.

y2kbmet

My 2007 5.4L 3v slips similarly to how you are describing but it only does so when I am driving through neighborhoods around 25 to 30'ish MPH. Sounds like it's trying to shift into a higher gear, revs up and I have to let off the gas or it will slam into the next higher gear. It has done this for years. I overcome it by turning off the OD while driving at that speed. I doubt it's trying to shift into OD but for some reason this works.

Now I'm getting a weird vibration or shudder as if I'm driving over a cheese grader for a few seconds while going down the freeway at higher speeds if I allow it to easily shift into OD. I've also learned to overcome this by not letting it shift easily so as I hear it getting ready to go into OD, I have to give it little quick burst of gas to make it shift quicker and then it doesn't do it. I did just put 4oz of the friction modifier in the rear end, changed all the plugs, cleaned all the COPs and it's a little better, but still does both.

Weird stuff w/ these tranny's. I wonder if anyone else is having these tranny issues? Hope you get this tranny thing figured out bud.

Ron R

My 2007 does it too, I'm leaning towards this TSB

Ford TSB 08-14-3

Some 2007-2008 F-150 and Mark LT vehicles built between 12/4/2006 to 5/20/2008 and equipped with a 5.4L 3V and 4R75E, may exhibit an engine RPM flare during light acceleration during the 3-4 upshift. This would only occur at road speed ranges from 25-30 MPH (40-48 Km/h). No DTCs or other drivability or transmission issues would be present.

ACTION
Reprogram the powertrain control module (PCM) to
the latest calibration using IDS release 54.5 and
higher. This new calibration is not included in the
VCM 2008.3 DVD. Calibration files may also be
obtained at www.motorcraft.com.

I had cheese grater too, drain and fill transmission along filter replacement fixed that problem. I used of can of electronic cleaner to spray around the valve body to get rid of more contaminants.

y2kbmet

Ron - outstanding info. I can't wait to try both. Question for you: Were you not afraid to drain, fill and change filter on the tranny? I've heard if it's never been done, it's better off left alone. OR is it that you've been regularly changing the tranny fluid? Also, how many miles on yours when you did it? I've got just over 150K on mine right now. Thoughts and thanks in advance!

Ron R

It can be a bit of a messy job but it’s not difficult. I have 4 trucks and have dropped the pan on all of them changed filter and new fluid. A few 8mm bolts, some creativity getting some off that are hard to access. I think I used a ratchet wrench to get hard ones off. I bought my 2007 with 160k on the clock and was probably original fluid. If you click my profile, I think I’ve posted some of the projects with the truck. When accelerating usually getting on the highway sounded/felt like driving over a rumble strip-fluid/filter changed definitely fixed it. If you get bucking/hesitation on easy acceleration or uphill usually around 45 mph, that would be coil pack dropping out in my opinion. Like others have said, change plugs and clean spark plug wells and I use Torque pro to see if any misfires and on what cylinder, no need to buy all new coils just fix the ones that are identified as bad. I used a long 3/8 extension with a old white tshirt soaked with carb cleaner at the end and wiped them clean, spark plugs out of course. I did not use any dialect grease on coil boots and no antiseize, personal preference, seems like causes more problems than it’s worth. I’ve got some new motorcraft coils if you need them, just sitting in my garage if you need replacements, I bought a whole set but just ended up using originals. If you’re near Houston, I would be happy to help you out. Locking extensions and magnetic 9/16 spark plug socket helps tremendously. You can do this.