Long time since I've whined on here, but just thought I'd post the latest development in my rough idle fiasco. To summarize (again), my 2001 L with 4900 miles vibrates badly at idle (so bad it feels like an electric razor when you grip the steering wheel and it will ripple your coffee too). Anyway, new plugs and MAF did NOT fix the problem. The dealer's diagnostic computer couldn't really pinpoint any problems, and everyone was confused as to why the truck was running so rough.

Today they let the shop foreman take a look at it. He's revered as some kind of god over there, and has an impressive reputation. Apparently he doesn't fix anything himself and specializes in diagnosing the mystery stuff and the management doesn't care if he takes 2 weeks to figure something out. He has the first bay in the shop, and works autonomously. Anyway, this genius has concluded that my engine is not idling rough at all, but in fact the whole truck is shaking because of a bad "exhaust dampener." I'm not sure where this thing sits downstream, but apparently it's also responsible for the "flutter" that I mistakenly assumed was a slight miss under load in top gear. The exhaust just drones and makes the truck feel rough at those RPMs. I guess that explains the "rough" idle and sensation of missing, but shouldn't be related to why I am getting less than 11 MPG. They claim the fuel trim is perfect, so maybe the L just sucks down the gas with all these cold weather starts.

The new part is supposed to arrive tomorrow, so we'll see if this fixes it once and for all. I was a little skeptical at first, but seeing as this guy is supposed to be damn good at identifying the most unlikeliest culprits, I'll give him the benefit of the doubt for now.

Any reason to think my vibration would cause any long term problems besides maybe wearing out the engine mounts a little sooner? I've always heard that vibrations can kill an engine.

Will post results tomorrow for sure - everyone check your exhaust dampeners in the meantime.

 

Thats interesting, I have heard of Exhaust doing funny things people. I am guessing this is the thing that looks like the pre-cat? One on each side after the manifold? Let us know if it helps or not!!. I am guessing they are getting you a new cat pipe since it is all welded from the factory.

 

The only people who have exhaust dampeners are those who had a vibration and sorted it out this way. My Tech figured this one out last March. By the way, this was a big problem when the '97's first came out with side exhaust.

There are a couple of things to look at. First off, my truck when in park, when revved to 3000 rpm, would start a WUNG, WUNG, WUNGING sound that would get inside your head. Second, at about 90 mph, which is 3000 rpm in O/D, would do the same thing.

What my Tech did: There is an exhaust mount that is held in place under the rear transmission mount. This was cut off. The entire exhaust system had all connections loosened, form the cats on back. The truck was warmed up 'till good and hot. With a foot on the brake, the transmission was shifted from forward to reverse a few times, to get the exhaust system to re-seat itself, and then everything was tightened back up. And last but not least, the exhaust dampeners were used to replace the front clamps on the muffler.

Failing all of this, a Magnaflow muffler was used and it got rid of all this crap. Many have used the above technique to good effect.

 

I don't know exactly what it is included, but they did say it's a special order item. I may go down there and check it out tonight.

WHAT04, are you saying that there should not be an exhaust dampener installed from the factory?

 

Not at all. This was a cure performed by many who experienced the conditions I described. No dampeners from the factory.

 

I think these are the parts they are ordering. I had the exhaust dampeners installed on mine. My truck never shook at Idle only at certain speeds.

here is the first pic: look just infront of the muffler.

 

in this pic you can see both of them

 

Opps forgott to atach the 2nd pic

 

Wow, those things are crazy... not what I imagined at all. How much weight does that add anyway...

 

Ben I have no idea how much they weigh??

WHAT04 and myself went throug the vibration thing last year on our trucks. The procedure he posted is exactly what you may end up doing.

In fact if it wasn't for him I wouldn't have known what to do.

 

Thanks Don and WHAT04... I don't want this problem to return and will make sure they go through all the steps described above.

Will I have to repeat all of the steps if I decide to get a Bassani cat-back or something similar down the road?

Also, now that I think of it, why are only some F-150's/Lightnings afflicted with this problem.

 

Most of the issue is from the exhaust neutralization (ie. the loosening, heating and retightening). Regular F150's have a longer exhaust out the back which dampens the vibration. Our problem is just an assembly issue I believe.

Installing the Bassani catback will eliminate the problem also. Don C. put his weights on with his Magnaflow as I did. But I have since removed them without ill effect.

 

My dad just picked up a 2000 L the other night, used w/ 4k, a few minor things.....but the biggest seems to be exactly what you are talking about....I mentioned it to Don the other night. Engine seems to run rough/miss at 3k-3.5k, and when in park and idling there is a vibration and a inconsistant rattling sound comming from under the dash/behind passenger front fender. Seems to be exactly what your talking about. When driving, you can feel a vibration under the floorboard right near the transmission hump on the passeger side. It's going in the shop wednesday.....i'll mention this.

 

Ben,

I really don't have much to add about your problem, but what dealer are you going to???

I am just curious!!!

 

Tallimeca:

Having been a proud owner of an '00 as well, I can help you with the vibration on the floorpan. My guess is that it doesn't happen when nobody is in the passenger seat. Was once refered to as the "three man rattle". The problem is that the muffler has been raised just a bit too much and is hitting a seam that passes just above it near the front. It's barely visible from below, but you can feel it if you put your hand up there. If you can believe it, the floorpan sags just enough with a passenger in it to rattle against the muffler.

Just loosen up the exhaust system bolts and pry the muffler down a bit. You might have to heat the rear hangers and bend them a bit to move the muffler down. Worked for me, but I was never able to get the exhaust tips snugged up into their cut outs like I wanted. Actually it was an attempt to do this that caused the muffler to get too close to the floorpan in the first place.