Engine running rough - timing chain related?

About a week ago, I started hearing a very faint marbling sound from the front of the engine. I could only hear it while standing at the front of the truck and at the wheel wells. I thought it maybe the belt tensioner or pulley going up, so I removed the belt and ran the engine; still there.

I then began to think that maybe the timing chain tensioners are finally kicking the bucket. The X never had the TSB done that I know of, as it has never had any engine issues until now at 158k. It was purchased in 2001 with ~18k on it, so I doubt the previous owner had it done, and it was well beyond the warranty from Ford by the time I found out about the TSB.

Now that I have this in mind what the problem may be, I started looking at getting the replacement parts so I could fix it up sometime later this year when I have enough time to do it myself.

Here's where it gets interesting.

About 3 days ago I started noticing that it had begun to idle rough. No real driveability problems, just at idle the RPMs would dip and the engine would give a shake. Normally idles between 650-700 RPM, and has for a long time....but smooth.

Now yesterday and today, things are getting worse. The rough idle has gotten worse, as well as the rattling in the front of the engine. They now coincide; that is, everytime I hear a rattle, the RPMs dip and the engine shakes, and it is happening more frequently now too. There is no rhythm to the rattles, its just random.

Also, I can notice this while driving too, so it is no longer isolated to the lower RPMs. I have felt it from 600-2500 RPM while driving (I try to keep RPMs low during normal driving, so I haven't been higher than that, nor do I want to with these symptoms). Under acceleration you can feel a slight bucking or hesitation type feel, as well as when cruising, but it is not as pronounced then.

So, does anyone have any ideas what this could be? My thoughts are that one of the timing chain guides or tensioners recently failed thus causing the rattling, but I'm still kind of stumped as far as the engine running rough. I was thinking maybe the chain skipped a tooth or something, but I figured if that happened, it would be MUCH worse than it is.

Any help is GREATLY appreciated, as I really need my X to get to work, and I would like to avoid a mechanic if AT ALL possible.

It's very hard to say by noise whether the problem is minor or massive. It may go like that for weeks or months, or it might not. I never experienced it really, I did the work on mine when I first bought it at 77k miles. If the chain is just a little loose from one of the suspect parts beginning to fail, it may be fine and not change if the rpm's stay reasonable. If you must drive it and can risk it, try to pay very close attention to the symptoms. If anything changes then you should reevaluate whether to drive it any more. Regards,

when mine let go, it was very sudden. I lost almost all power and the truck would not idle at all. I give it a little gas to keep it running. I didn't hear ant noise though. A friend of mine has a 98 sohc and it been making a rattling sound for 40K miles. I would deffinetly keep a eye on it. Good Luck

When mine went, I had the same as Josh with horrible noises. I believe the top guide broke & the pieces fell down & killed all the rest of the guides. It almost sounds like you might be loosing ignition for a second, now & then.

Maybe its the intake o-ring thing? There was a TSB that had you change the lower intake gaskets (a series of o-rings), and at the same time, just becuase you had it apart and they knew there were issues with it, the front cassette tensioner (and this little plastic anti-drainback thingy, keeps oil in head for next startup).

The o-rings (vacuum leak) would explain rough idle and other symptoms, but not that this would be associated with the rattle (which indeed does sound like the front jackshaft tensioner issue, which is a different tensioner, and different TSB, than mentioned above).

But maybe it rattles more at this time because the engine is bucking? Like maybe the jackshaft chain is real loose, tensioner gone, and when the engine makes a rapid transition of speed (like when its almost stalling due to vacuum leak), it naturally rattles more?

If you do get the jackshaft tensioner replaced, I need your old part. Don't care if its all busted up, just need all the pieces (long story).