I have a DOHC 4.6L that's developed almost a 'lope' in the idle that is transmitted through the whole car when the motor's running as a harsh vibration. It's very regular, almost like a lopey cam would be, but this is a stock motor with stock cams, and there is no 'lope' to them.
This all started the other day when driving home. It was fine for a while, then while cruising at a constant speed on the freeway all of a sudden the car picked up a rough vibration. I thought I had chucked a wheel weight or something of the like and pulled off to check things out, only to discover that it's the motor that's vibrating.
When I got home I pulled plugs and wires and found a what appeared to be a bad wire, figured that was causing a miss and replaced it, but tonight I fired it up for the first time after replacing the wire to test drive it and it's little if not at all better. The same harsh regular lope-like vibration exists.
Any ideas? The RPM's are stable too. Could a cam have skipped a tooth or something and changed the physical valve timing in one of the heads? The motor's only got 114k miles, so I figure it should just now be getting broken in. It does have that gratuitous tensioner tapping on first-start in the morning, but it goes away after a second of running, and the car has to sit overnight or longer for the tensioners to bleed down again. Also, I had the driver's side valve cover off a month ago to change the cover gasket, and the chain wasn't loose or anything unusual.
This all started the other day when driving home. It was fine for a while, then while cruising at a constant speed on the freeway all of a sudden the car picked up a rough vibration. I thought I had chucked a wheel weight or something of the like and pulled off to check things out, only to discover that it's the motor that's vibrating.
When I got home I pulled plugs and wires and found a what appeared to be a bad wire, figured that was causing a miss and replaced it, but tonight I fired it up for the first time after replacing the wire to test drive it and it's little if not at all better. The same harsh regular lope-like vibration exists.
Any ideas? The RPM's are stable too. Could a cam have skipped a tooth or something and changed the physical valve timing in one of the heads? The motor's only got 114k miles, so I figure it should just now be getting broken in. It does have that gratuitous tensioner tapping on first-start in the morning, but it goes away after a second of running, and the car has to sit overnight or longer for the tensioners to bleed down again. Also, I had the driver's side valve cover off a month ago to change the cover gasket, and the chain wasn't loose or anything unusual.
