My 15 passenger 2002 E-350 with the V10 is missing (or mis-firing? It isn't actually gone). It has about 160K miles on it and I don't know much about it's service history prior to 130k. Nothing major has been done on it since I bought it.

Recently it started missing, or at least that is what it seems like. Problem is, it only does it when it is warmed up and idling in gear. I can not feel the miss during acceleration or going uphill or when it is cold.

The only other problem to accompany this is a tinny hissing sound that seems to happen under moderate acceleration, before a shift. I don't have a tach, but I would said that it is about 2500 - 3500 rpm going from 2nd to 3rd. This doesn't happen all the time, but is fairly consistent. It does not seem to me to be a vibration sound, like I have read some others mention is common with the motor, and it is a new sound. It will last from 1 - 3 seconds, often there is a very brief pause in the middle.

My mechanic said he hooked it up to the mode 6 diagnostics but could not identify which cylinder was missing. He replaced a couple of the coil packs but this has not solved the problem (it may have made it a little better but I'm not sure) and I don't want to have to replace all of them.

My family needs this vehicle to be working well. Any ideas?

 

I can't blame you for not wanting to replace all the coils, but since you do not know the vehicle's past repair history, coils do provide intermittent problems which mode 6 should have picked up. Vacuum leaks will tend to even out when RPM is raised. With unknown history spark plug replacement is always a good move. You need to start somewhere and plugs are routine maintenance items. Plugs good for 100,000 miles are a salesman's line not a serviceman's line! We know better.
Intermittent problems cannot always be found even with the best equipment, but symptoms can help narrow down some problems.

 

I'll see about replacing the plugs, any idea on what might be causing the new noise and if the two things are even connected?

 

Sometimes folks can place a video on the forum where we can hear the noise in question.
It is pretty difficult to even offer an answer without hearing the noise. Can you be a little more specific as to where it sounds loudest, like front , rear, driver's side , engine compartment, under the vehicle ?
Many times the operator/owner/customer has a pretty good idea where it is coming from and can be very helpful. What do you say?

 

If a person were driving, and they drew a line straight from their head to the ground under the right front tire, the sound seems to be coming from that direction. Which basically means it's coming from the engine compartment...

That being said, I will attempt to get a recording of it this weekend sometime.

 

I had a terrible problem with my '98 E350 (V10) missing for several years. No guarantee that the cause of my problem is the same as yours, but just in case, here goes: I just drove it missing until I figured out what the problem was. I had the bad coils replaced several times and the spark plugs replaced twice, but the problem always returned when it started raining. If your mechanic's scope isn't identifying the bad coils, go to someone else - they should show up. And in my experience, once the coil gets wet, it misses forever - you have to replace it. Turned out the rain "gutter" under the windshield was poorly designed. Several components bolt to the gutter and where they do, the edge is very low. The slightest amount of dirt or moss combined with a rain will cause it to overflow and dump water on the coils. What I did was unbolt all the components bolted to the gutter and clean it thoroughly. Then I took a piece of Z flashing, meant for water proofing between pieces of T-111 on your house and bent the short side back on itself to make an edge that wasn't sharp. The flashing is then in the shape of an "L" instead of a "Z". The flashing is thin enough that it bends easily. I put a piece of the modified flashing with the non-sharp edge up on the gutter and drilled holes in the bottom flange everywhere a bolt was supposed to go through. Then I bent the brackets for the air cleaner and other components so they would go over the flashing. You may have to take them off and do some creative hammer work in a vice. Be careful not to bent it to sharp so you don't break the bracket. I bolted the flashing to the gutter with a generous bead of polyurethane caulking under it (I used Vulcum 116, available at Home Depot). Then I bought some stand-off spacers and longer bolts of the same diameter and thread that previously bolted the components on, at my local hardware specialty store and bolted the bent brackets on over the new flashing on top of the stand-offs so that it didn't bend the edge of the flashing down. The flashing was as long as I could make it so it would carry water away from the engine. The flashing is about 3/8" to 1/2" high and works great. It's butt-ugly, but you have to open the hood to see it and it's worth it not to have the problem anymore. I've driven from western Oregon to Idaho in driving rain and several months since in rain and it's still running strong! If anyone needs further help with this, please let me know.

 

Sounds like a fix!