I am trying to fix a 1989 240sx automatic w air. I have a dually, but with diesel prices, I need to save some money. This car used to belong to my sister and she parked it for dead at my father's a few years ago where it sat until now. So far I have had to clean the gas tank, replace the fuel pump, fuel filter, something chewed through a lot of the wires by the engine; fixed that, and the computer said my engine temp sensor was bad...(code13). Now my computer says (code 55) all ok; but it idles like crap and has no power at all. It had some noise I couldn't place, so I take the valve cover off and I see half of the timing chain plastic guide (facing the car on the right side) I see half of this laying about half way down the engine, I guess the rest of it is stuck to the pick up tube in the oil pan in pieces. Anyway, what causes that to break and what would cause it to run that bad?? I realize that it is going to take some time and work to replace that and the timing chain as well. I will need to get in that oil pan and clean it all up, too. I am going to check the compression today and see where it is. But, do you think it is worth it? It seemed like a good idea at the time, but I am running up a bill now and the time I have spent is crazy, too. If the computer says code 55 could there be something else wrong causing the thing to run that bad? That is misleading, it doesn't seem to run too bad. It just idles rough but it will rev up to 5000 - 6000 and doesn't sound too bad. But when I drive it around the block it just won't go. I would appreciate any help. As you can tell I am disheartened...
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One more thing, how do these lights work? Do the motors turn the same direction for up and down and the voltage applied by time or do they rotate one way for up and one way for down for a period of time.? There doesn't seem to be any feedback as to whether they are up or down?

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Mine are always up.. I can turn them down by hand but then they are back up. I guess that is better than being stuck down, but as I can't get it to run right it won't ever matter if the lights work, huh??

I just finished doing the timing chain tensioner in my truck, 97 Hardbody, which has a KA24E like your car. I can't imagine they're set up too differently. I can tell you that it wasn't the easiest thing ever, but it is possible to do at home. Off the top of my head I can tell you everything I had to remove: radiator, power steering pump, air conditioning pump, water pump, oil pump, distributor, valve cover, literally everything off the front of the motor. I also had to remove the alternator because I broke a bolt in the oil pump that I needed to torch out, so you shouldn't have to remove the alternator as I did. I decided not to drop the oil pan because in my truck that would involve lifting the motor and I had no reason to drop it. You can slide the front cover out even though it's sandwiched between the head and the oil pan.

If you do plan on doing this job yourself, and you would like to get it done in a timely manner, I can only suggest that you get everything you need before you start. Fresh oil, coolant (if you aren't reusing whats in there already), timing light (since you're completely removing the distributor), pulley remover (for the crankshaft pulley), Black RTV sealant, waterpump/thermostat housing sealant, and any new parts you can afford. I personally told myself before I started that since I would be removing everything anyways I might as well replace it. I ended up replacing the oil pump, water pump, and valve cover gasket even though they were all originally fine. In the end I totaled about $300 in parts including the chain tensioner and guide, and I know I won't have to worry about anything for a while.

That's just my story. If you decide to tackle it I hope everything goes as well for you as it did for me.