2006 Limited 4.6 - severe bucking at 1/2 to 3/4 throttle

[Ziggy75]

Hello all.. I am new to the forum and just recently purchased a 2006 Limited with 4.6. It has a check engine light and shows a P0446 code related to evap. I have found that it will occasionally buck severely at 1/2 to 3/4 throttle. I let off throttle and power comes back. It doesnt do this all the time. I am also noticing a slight vibration at highway cruise when depressing throttle to maintain speed. Once throttle is let off the vibration goes away. It is very slight. Almost like a spark issue. Anyway, I bought an actron scanner last night and was viewing some data today. I noticed when the bucking issue is happening my TPS % goes from roughly 77% down to 22% and then up to 65%. So it leads to me to think something with TPS. But wait... this is drive by setup. Ive never owned one of these before. Could the drive-by be causing it? I have no codes that indicate a misfire or any sort of the kind. I cant believe my P0446 is causing this. Any help would be appreciated.

 

[Ornery]

I'll hazard a guess. Sounds like a plug not firing under load. So, I'd replace the plugs (easier said than done), and swap out coils if that didn't do the trick. I've got cars I can snitch coils from, but if there's quite a few miles on the plugs I'd replace them anyway.

Not even going to begin to guess how to decipher your scanner findings. The plugs are something in need of regular service anyway, so no waste in replacing them, and you should be able to obtain a known good coil or two for cheap.

 

[Ziggy75]

Thanks for the suggestion. While typing out me post, I was thinking about the plugs. I know that I dont want to jump into a whole lot of stuff until I check those plugs to see at least what they look like. The Explorer has 138,000 on the engine. Assuming they are original then they are due for a change anyway. What is the general practice when installing the new plugs? Should I use anti-seize? I am new to the 3v crowd and only have experience with my 04 Expedition 5.4.

 

[Ornery]

Hah! Sorry, I chuckled when I read your last questions. But, at least that's something I've had experience with...

My Spark Plug Endeavor​

You know, once upon a time, we used to have to change plugs every year? As well as new points, cap, rotor and wires every couple years? Never would have imagined being able to go 50 or 100K on the same plugs, let alone 138,000! It won't be easy, but it is overdue, and the obvious first step.

Good luck!

 

[Ziggy75]

An impact gun? Interesting... I will have to look into this. I cannot believe how expensive these plugs are!

 

[Explorer_PL]

I think the price of the plugs is the least of your concerns.

Read more here:

http://www.explorerforum.com/forums/showthread.php?t=377511

 

[Ziggy75]

For a moment you had me worried with the TC. The thought did cross my mind the other night when I was feeling this slight vibration. It doesnt do it all the time. You can start it up and drive it and it runs great. Then 5 minutes later you will feel a misfire while accelerating at a slight load. I am sure the plugs will help. We will see...

 

[White97Jimmy]

I've had both of these issues and solved them. Both are not probably what you want to hear.

Throttle issue is your spark plugs. Once you change those out, it will be much smoother. However, if you plan to do this yourself, make sure you have the plug extraction tool. I broke several plugs in mine and had half as many miles as you do.

The shifting issue can be solved in a PCM update. The dealer did this for me and is not covered under any warranty. I believe the cost was about $170 and a full day spent at the dealership.

 

[Ziggy75]

I think I am experiencing a transmission problem and not a spark issue. The reason I say this is because I was just driving it and at full throttle the power cut out like it would if traction control kicked in. But when the power cut out I felt a kick and then the tach raised up to around 3500 rpm and then it went back down and another kick and I had my power back. Nice eh? This is what it has been doing except this is the first time I actually saw the tach raise up.

 

[Ziggy75]

After doing some research on this forum I found that there is a dipstick and so I checked the level. The fluid appears to be around 2 quarts low. Looks like I will be getting some Mercon SP tomorrow.

 

[Ornery]

Sounds like your machine could use normal scheduled maintenance overall. It's probably due for trans fluid change. Already know the plugs are due. Coolant is probably ready, too. A little TLC now could pay off big in the long run.

 

[Ziggy75]

Alright, I picked up some mercon sp tonight. I was able to get about a quart in before it read 'full'. I went out and drove it and found that it doesnt rev like it use to. However, it does seem to let 1st gear loose at about 4700 rpm. I plan on doing a plug change in about a week. It was my intention to do a full fluid and filter change this summer. I dont know if my issue would be corrected with a fluid change or not. That being said, I dont know if I should pay to have this done now or wait until spring when its warmer and change it myself with some Amsoil. I listed a link with youtube showing a video of my issue. It is night and day difference with the extra quart of fluid. Before it would let loose and rev then slam back into gear. Now it just appears to let loose and then shift but without a rev. You can see for yourself at around 4700 rpm.



http://youtu.be/dfx6iaoiLBY

 

[Ornery]

Don't forget the filter replacement. That may very well be causing your current problem.

 

[Ziggy75]

Thanks for the suggestion. By the way, is that gasket reuse able on the pan?

 

[Ornery]

Congrats on getting the plugs out. That's a little concerning about leaving porcelain in the cylinder.

Better be extra careful with the trans fluid change. Apparently, the gasket is reusable:

 

[Ziggy75]

Thanks for posting this information. Once I realized that a portion of the porcelain fell into the cylinder I really didnt know what to do about it. I couldnt even see it in there through the hole. I tried using an air compressor to force what I could out but I doubt I got it. There was also the portion of the metal from the bottom of plug that broke off and was left in cylinder.

 

[Nsa-sog]

I had the same problem last month. The problem was coil pack #8 had a resistace priblem causing ainterferance within the wire loom ditectly over it.. Next to the brake booster.. The coil pack trsted good but had a internal short.. The repair cost was 34 bucks on ebay i replaced all the coil packs while i was under the hood.. The missfire and bucking went away after i cleared the codes.. Ive read where people where rebuilding the transmission and still having the problem .

 

[WaltZ]

I had the same problem. No CEL. I also live off a gravel road. I ended up getting some MAF cleaner and clean the sensor. All was well.