Bad Motor/Tranny Mounts?
 

Gentlemen,

To make a long story short, the truck ('07 5.4L) has been idling rough and bucking/shuddering around 2200rpms.....mostly when going uphill. Had the same problems a few months ago, but they seemed to go away after I replaced the coils (plugs were changed shortly before the coils). I've noticed that both symptoms are more pronounced when it's colder outside. The past two weeks it's gotten colder, which is why I believe the problems have returned.

For the shuddering, it goes away if I let off the gas or give it a little more. The rough idle is sometimes there, sometimes not. When it is there, it seems turning on the A/C and increasing the load on the engine makes it worse. It's gotten bad so when pulling up to red lights I've been throwing it in neutral to lessen the vibrations.


Thought it was my catalytic converters since they were likely fried in the process of me determining the coils needed replaced. They were also the only CEL codes that were ever thrown throughout this entire process. I had them replaced today but the problems are still there. One culprit eliminated.




Now I'm leaning towards the motor and/or transmission mounts. Anyone had symptoms like this in the past? What was the cause?



I took a video (below) of the tranny while I switch gears (P-->R, R-->D, D-->R, etc...). It looks like there is some movement in the transmission. Pay attention to the top left side of video (transmission case). When I'm changing gears you can see it shifting ever so slightly. Not a lot, but it is noticeable. When I start the engine it also appears to move a bit. This would mean my transmission mount needs replaced, correct?


Also, if it does, then am I correct in assuming that I might also have a bad motor mount (causing the rough idle)? Don't have a video of the engine, but when it's idling rough the engine does move a bit. Not a lot, but enough to make me think the mounts might be starting to go bad.



Please click on the video and make it full-screen to see it better.


http://www.youtube.com/watch?v=xoLFtFn1QP4
















Also, on a side note, does anyone recognize what component is causing this sound? It's louder in the video than in person. Unfortunately I'm not super-mechanically inclined. :o

http://www.youtube.com/watch?v=4FyxsidjM50

A bit hard to tell due to the angle, but that u-joint looks like it might be shot.

Some amount of shake and shift is normal - there's rubber in the mounts to let it do just that without transferring all vibrations into the truck.

Yeah I have an oil change coming up soon and that u-joint is on my list to be looked at. You can hear in the video that there is a slight squeak/clunk when changing gears.

If the transmission is okay like that then maybe it's not the mounts. I'll be checking the vacuum lines tomorrow morning. Unfortunately there are a lot of things that could be causing my symptoms.

Took a video of the engine today....first time I've been able to see it.

Looks to me like an engine mount softening and starting to go bad. This could be causing my rough idle and bucking at certain rpms, correct? Any thoughts?




http://www.youtube.com/watch?v=NC0Qc-hTdCs
http://www.youtube.com/watch?v=bbN8ysjxrmk

I don't know a ton about cars, but I have replaced a few engine mounts when I had automotive class a few years ago and they all did the same thing yours is doing before the mounts were changed. It could be causing the bucking and rough idling, but I don't think it would.

Matt, any updates?

Yep, John, it turned out to be another bad coil. :p

I had assumed that with new plugs/coils that those could be eliminated. No more assuming.


Turns out one of the coils I had installed (far back passenger side) had a small broken tab. It wasn't completely broken, but the electrical wires run through it, so it must have been enough to affect things. Moisture probably got in there.


Got the truck back earlier this week and so far so good. :wave:

Geez that sucks, good to hear Matt :thumbsup: Now I like you, had a coil go bad last December. 1-2 months prior to that I started getting a P0430 that would go away and come back. Well turns out Coil 3 was bad and I had 5 fouled plugs. Once the work was done, the code stayed off for a month or two, then came back a few times over a weeks period then stayed off until the other day 9 (7 months). I'm wondering if my cat is bad, were your bad after your coil the first time?

Yeah I've had P0420/P0430 off and on for the last few months, also.

Before I found out it was another bad coil, I thought it might have been the cats causing a rough idle. A few weeks ago I had them replaced and my exhaust re-welded completely (with new mufflers and whatnot). It didn't fix the rough idle problem, but I haven't had the codes come back on since.

From what I've read, bad coils/plugs can kill your cats if they go for too long (which mine did). Too rich a fuel mixture and they will get clogged, for lack of better terms.

If you have a bad motor or trans mount you will know, you'll have a nasty vibration on take off.

Yeah that's what has me wondering Matt, my mileage is pretty good. I average 20 on a trip to Maine this summer and average 16-17 for mixed driving each fill-up and that's with my heavy tires and Roush Wheels. What I can't tell is if certain coils correspond with different converters. I.E. if 1-4 go bad... x cat gets raw fuel and if 5-8 go bad, y cat gets raw fuel dumped. The coil iirc was #3 and my truck is throwing P0430, so I can't tell if that would have caused it.

PS, how are you liking the ProXS mufflers?

1-4 is Bank 1, 5-8 is Bank 2. Therefore, coil #3 is not related to a P0430, which is Bank 2 below threshold.

Could the 5 fouled flugs the dealer found last winter be the culprit? I'm just confused why I had no codes ever (hi flows were installed in April of 2010, then October of 2010 P0430 came on and off, then 5 fouled plugs and a coil were found. Once fixed, it stayed off for about a month. Once it finally cleared I got inspected and haven't seen it since Feb of 2011 until Tuesday of this week. I'm baffled

Just dug up my old invoice...


And also to add, I replaced a bad thermostat last week and this summer I saw normal Cylinder head temps of only 188 degrees or so. This was going on last winter so I wonder if the truck was not reaching closed loop. Other than that efficiency code, I have not noticed anything strange other than a small shake at idle every so often. It's only in park and I wonder if that is the engine skip the dealer was referring to

Are the O2's still original? They may be fouled enough to cause poor running but not enough to trip a CEL.