My sister recently bought a 97 expedition. It has 265k miles and needed some work. I replaced upper and lower ball joints on both sides as well as inner and outer tie rod ends. I replaced the stabilizer bar bushings. Now the only thing it seems to have is a shimmy/rattle between 35 and 65 mph when the Rpms are between 1300 and 1800 only when on the throttle. If you let off it stops doing it. As well as if you turn the overdrive off and the rpms go over 2000. It happens in 3 rd and overdrive. Does anyone have any clue what this could be?

 

Do you feel the shimmy in the steering wheel?
Do you feel the shimmy in the seats or floor pan?
Do you feel the rattle or only hear it?
Does it happen in park or neutral at that rpm?
Did you inspect the rear driveshaft u-joints?
Did you inspect the rear pinion shaft for play?

 

It does not happen in park or neutral. It's only when driving. I checked the driveshaft and there is no wiggle or play in it. You can hear the center consol rattle and you feel the shimmy in the steering wheel. You also feel it through the pedals. It does run a little rough when idleing but is doesn't seem like the same shimmy

 

Any idea when it was last tuned up? It sounds like it might be a misfire. often they seemingly disappear as rpm increases. It may still be misfiring but it is hard to detect because the engine fires much more rapidly. Also higher rpm and lower throttle inputs decrease cylinder pressures making it easier to fire the spark.

Try loading the engine while in gear and holding the brake. If it does it then, you can be sure it is not something that rotates. You should easily be able to get the engine to those rpms while holding the brake.

 

I was told that the plugs were recently done but I pulled number 5 coil pack to look at the plugs and they are defiantly not newer. That plug is real rusty and the hole seems real wet. Does that mean the head gasket is shot or could it be from something different?

 

Probably just means that the spark plug boots aren't sealing very well.

Leaking boots aren't good and could easily cause a misfire.

 

i replaced all the plugs and boots. It stopped the shimmy. So you don't thing it's an issue that it was wet then? And do you think replacing the boot will stop that?

 

I think there was water in the spark plug hole because it needed new boots. Fix the boots and it should fix the leak.

It is always good practice to put a healthy dab of dielectric grease in the boot before putting it on the plug. That way, even If the boots let water down in the hole, the dielectric grease should keep the water away from the plug so it doesn't misfire.

I'm glad that the new plugs and boots fixed the shimmy! That a pretty easy fix

 

Glad to hear that stopped the steering wheel shake.
Depends on what the "wet" came from. If the plug well is wet with oil, probably the valve cover gasket is leaking. If its wet with coolant, you might have a heater hose connection that is dripping a little coolant into one of the plug wells. If it is wet with water, might be the hood to cowl seal is letting water drip into some plug wells.
If it is filling up with liquid, the new boots will eventually arch to the liquid. That's just my guess.

 

Thank all of you for your help. I did not know that the spark plugs would cause a shimmy like that. Are there ways to tell if a coil pack is bad or just a guess if that cylinder isn't firing?

 

if the misfire is bad enough, you should see your check engine light flash. if that happens then there will be a code stored in the PCM telling you which cylinder to look at. More than likely, that's going to be your bad coil.

now... that being said, a misfire won't always set a code, and those can be a bugger to chase down.
https://www.ford-trucks.com/forums/1...pid-coils.html


the other way is to have someone with a high-end scan tool look at the cylinder balance. if there's a consistent difference in the cylinder balance, or if one cylinder is consistently "twitchy" then that's a good starting point. in the end (for me), it was the scan tool's cylinder balance data that told me where to start to fix mine. cylinder #5 kept going negative more than the others, so I started with that one. turned out to be a shady coil on a worn out spark plug was causing the intermittent misfire. the new coil would fire the plug better than the older ones, but still would miss once and a while. but without that info from the scan tool, I wouldn't have had a clue where to start.


as to the spark plug boots - as alloro said, if it is oil or coolant, then it has to be a leak somewhere above them. Water could be a leaking cowl. check your cowl for a gasket, if it is missing or damaged you are going to want to get it fixed. My cowl gasket was missing when I bought my truck and I played heck finding a new gasket. I ended up having to get a cowl out of a salvage yard just to get the gasket. which ended up being OK because the clips that hold the cowl down were broken, so I needed a new cowl regardless. the body shop supply store in town did have a gasket that would have worked, but the cost on the gasket was the same as a new cowl, so I just went that route.


but, it could be just from rain water. you'd be surprised how turbulent it is under the hood of the truck. I've actually got rocks sitting up by the coil boots just from driving gravel roads. in fact, I had to blow a rock or two out of the spark plug well when I was messing with the coils and plug (only got one done so far, so you are doing far better than me!).


It could also be that someone sprayed the engine bay down with a hose or pressure washer. I've been known to wash an engine bay once and a while, and if your boots aren't 100% you are almost guaranteed to get some water down the spark plug well.


all of these reasons is why I strongly recommend dielectric grease. it's just a belts and suspenders thing. it makes the boots much easier to remove later when you do the plugs again, too. keeps them from getting stuck to the plug.


Good for you being able to help your sister with her truck. The amount of headache and money you have saved her already is a really great thing to do. good for you!

 

Great post - learn a lot from others experience