2005 F150 with 125K on it,

had it checked over in Jun before we drove 1300 miles to TX, I fixed what the shop suggested, new ball joints, new plugs (theysaid dont bother witht he coils or wires)

so recently, when it's wet out, it "shudders" (almost like a cylinder is not firing)when I'm leaving the driveway to drive a mile and stand in line to drop off the little person who eats all of our food....on days it's dry- no problem

-no lights on, on the dash...
-i've been thru several tanks of gas and it's not that...
-put it in Neutral and it still does it...
-stays like that for a few miles until the thing heats up...
-talked to my dad who thinks it might be a "transmission sensor"

any input would be helpful

Added, it's a 5.4 Triton engine

This message has been edited. Last edited by: MikeinNC,

F150s in those years are notorious for going through coil packs. They will start showing symptoms before they start throwing codes. I would bet money on a coil pack going bad. My buddy and I both had 2003s and we replaced several on both trucks.

This has nothing to do with rain, motor/trans mounts?

Mine would do something like that at low speed (start/stop) traffic or reversing very low speed. Engine would shake like it was about to come off the mounts. It would do it intermittently but always at low speed. Push on the gas or put in neutral and give it some gas, would isually go away. Turned out to be the VCT valve/sensors. They have 2 (one on each side of the engine at the front of the balve covers.

Also coil pack can make it run rough as well but not the shudder I described above. Coil packs will throw a code that is easy to find which one is misfiring. The VCT valve dis not show any codes or check engine lights for me.

ETA: 07’ F150 w/5.4L

I'd guess coil packs too. Although, my F150 had a small vacuum leak from an obscure vacuum line clear on the back of the motor (5.4L) that yielded similar symptoms, but they were pretty much constant. It took me months to find it and the part I replaced (plastic elbow) was less than .50 cents.

quote:

Originally posted by MikeinNC:

on days it's dry- no problem

If I read you correctly, your problem is associated with humidity.

I had a Honda that would stumble or quit on rainy days. It turned out that insulation on the ignition coil was breaking down when it got wet. The way I found it, I was almost home one day when it started to rain. The rough running started, I got home and into the garage while it was still running. Opened the hood, did not turn the garage lights on, and in the dim light it was easy to see the arcing at the coil.

Replaced the coil and the problem disappeared.

Vtail: Yes, when it's wet outside...rain or heavy fog, but after a few minutes it warms up and goes away.....

Sigmatic: How does one check coil packs??

Sig77: I have not replaced the coil packs, never had a problem....

Timing? I had to have both my chains and all the guides replaced at about 110,000 miles. They were shot.

First thing I would do is inspect the coil packs for cracks in the housing. If there is a crack, it takes very little moisture to cause a short in the coil pack.

Good Luck

quote:

Sigmatic: How does one check coil packs??

I've had several go bad over the years (my truck is within spitting distance of 300,000 miles) and, as I recall, they've always thrown codes. I've usually just gone to a parts store and had them identify the coil with a scanner, and then just replaced it myself. Unless it's in a hard to reach spot it's usually just a few minutes to replace.


I would also add that I have probably damaged a couple when washing off the engine, as I noticed symptoms shortly thereafter. I don't clean the motor as often now.

Acting weird?

Tell it to straighten up and fly right.

Had 2004 - did similar, was told coil packs or phasers going. Don’t know as decided to trade in.

All of these guessing is useless. Have a qualified mechanic plata scanner into it and monitor power balance this will show which cylinder is miss firing. Or look at mode six for miss fire data

I have coil packs that are going bad but aren't throwing codes. The first time it was bad for close to 3 years before it finally threw a code. It was the #6cylinder.

It started up again this past spring and has done it all summer until now, when the humidity has gone way down. Now it's not doing it at all.

BMW coilpacks aren't cheap, that's why I haven't swapped them all out.

So, you can:
1) Replace them all - Not a bad idea considering your mileage
2) Replace one and then swap around until it stops - Good route if you don't have the cash on hand for all 6/8
3) Wait until it throws a code - It's what I'm doing for now.

I smell an ignition coil. Being as this is coil-on-plug ignition, there are eight of them. Even if it doesn't misfire long enough to turn on the engine light, it might still have a misfire code, which (if present) will narrow it down. If there is no code, past misfires may be able to be seen on a scan tool set for Mode 6. The technician can also drive the truck while observing cylinder contribution on a scanner, but it has to be acting up at the time. Also, if this is a 5.4 3-valve engine, this has the POS spark plugs that break in half on removal. If they have been done before you can disregard this.

squirt bottle and spray each coil pack one at a time.

Almost certainly coil packs, it's a known issue on the mod motors, and Coil Packs wear out. 125k is a good run. You should replace them as preventative maintenance.

You can get a full set of chinese ones on Amazon for $50-$60 that actually work pretty well, or you can spring for Delphi's or Motorcrafts at ~$40 a piece.

I would go ahead and do the whole set though, as if one went, others will follow.

If you have a 5.4 read up on the cam phasers as well.

ETA: That link is just illustrative. You didn't say which engine you have and there are a couple designs of the boots, so You'd want to make sure you get the right set.

Worn out plug wires will cause that problem, showing up only when it is rainy.

Mike, it's most likely the VCT sensors. Mine's in the shop for it right now. Same symptoms as yours--shuddering at redlights and stop signs, and it eventually progressed to where it was dying while idling. Giving it a little gas and keeping the RPMs up will (usually) keep it from dying. I was told by the Ford dealership it's require an engine teardown to fix.