Power Fade > Check Engine Light / Infamous Timing Chain rattle

[elmosiris]

I have a 1992 240sx SE, DOHC (stock KA24DE) that isn't very happy right now. Its been well treated, but with 167k mi on it, some issues are cropping up. I am its 2nd owner as of about 1.5 years ago, so I don't have full information on its maintenance before then.

The main thing right now is a wierd issue of power fade / check engine light. Originally the problem was this:

While driving at a constant speed, usually in the 2000 - 2500 rmp range, suddenly the engine would bog down and loose some power. A few seconds later, I would see the check engine light. By tapping the gas, the 240 seemed to "push through" the problem, regain its power, and the check engine light would go away. Over the course of a week this started happening 2-3 times per drive.

For general good measure I did an oilchange + oil filter + Magic Mystery Oil to help clean out built up gunk. At the same time, I noticed that there was old oil on the engine below the valve cover gasket, which was there before this whole problem started.... so I got a new valve cover gasket and slapped it in too.I did some research, talked to friends, and decided I should probably replace the PCV valve, because if it was clogged or stuck it would probably cause this exact problem.... So after a lot of cursing + help of a professional lift + tools + mechanic friends, I managed to change the PCV which is wedged in under the intake manifold and behind the alternator.

My 240sx felt 1000% better for about 1 day, with no check engine light, no power hesitation. It wanted to hit the autocross that day. The next day, the check engine light returned, and is now on SOLID at all times. There is a little bit of constant power loss, with moments where it gets better or worse.

Without an ECU reader (and with my year even with a reader), a check engine light could mean about 1000 things, but mainly I wanted to know how to approach this from here... what systems to suspect next, to keep throwing parts at it (fuel filter, O2 sensor), or just get a shop to diagnose it since I don't have very good tools + lift to use? Has anyone seen these symptoms before?

Also, my 240sx has developed the dreaded chain rattle. While I was doing the valve cover gasket I looked at the timing chain, and everything *looks* ok, but I don't have expert eyes with this. The dealership wants $1300 to do it. I've also read that there is a Nissan bulletin that part of the chain guide is not necessary, and can be removed to fix the rattle, but if there really is a problem with the chain, I don't want to encourage it to fail and send my valve parts flying everywhere. I have friends that work at + have access to a professional shop, they work on mercedes, so I could by parts for $78 and have them help me do it, but they are not nissan specialists, so we'd all be in new territory as far as the particular "gotcha"s of that job on a 240sx.Any suggestions? What to look for, experience with this?

Any help appreciated!

[spitz7985]

the power fade sounds to me like it could be the o2 sensor.

the timing chain is not that difficult if you know what you're doing. it took me a hellofva long time to do mine because i just figured it out as i went. some say you can do it without dropping the oil pan. i had to and have no idea how you would do it without dropping it. its not really that hard once you figure everything out. if i had to do it again, i could finish it in a weekend. one thing that slowed me down the most was losing/breaking bolts. MAKE SURE you organize and label your bolts when you take them out.