Why does my 240 run so sluggish?


My 89 240 SX 171K has been running pretty bad for awhile now. I finally decided to figure out what was going on because all the  mechanics could not figure it out no matter how much I spent. And I spent plenty. I have the service book and I started in the diagnosis section. I think I know just about everything about the car now but when I started I knew just about nothing. With a lot of patience and time in my garage I got to the bottom of the problem.

With the help of the book and one of the faq's on this web site, I found it to be the AIV. The AIV is located on the driver side between the exhaust and the air cleaner box. Its job is to allow air from the cleaner box into the exhaust  when there is negative pressure (vacuum) in the exhaust. Has something to do with the emissions exhaust mixture I think. It is NOT supposed to allow exhaust air back into the air cleaner box. Well, guess what? Mine was. You don't want this used air getting back into the intake. Another clue was oily residue on the air filter. I took the assembly out of the car with 3 bolts. Opened up the device with the vacuum control and found the reeds to be filthy and the gaskets underneath peeled off. After cleaning them with carb cleaner and a sos pad, they looked like new. I put them back together and still had air bleeding the wrong way. That is when I  noticed the gasket underneath was messed up. Unfortunately you can not replace it. So ! I bent the reeds so that they lied flat against the surface. The car runs normal now.

Servicing the AIV is really not that difficult. It almost looks like it should be opened and cleaned periodically. I have found that after awhile, work on the car becomes easier. You begin to learn how to check devices and vacuum lines properly. The book is pretty good about showing you how to diagnois components. I was frustated at first, but am looking forward to learning more.

Some other problems I have had that are probably common. High idle speed caused by a corroded air regulator connector. It is the connector under the fuel injector rail. Seems the rubber cover on most of the connectors cracks and allows water into the connector and does major corrosion over time.

Another piece of advice. Don't replace the fan clutch with one from Autozone. I went through 2 bad ones. One locked up and the other makes a load air flow noise when accelerating. Go ahead and pay the $100 more for the Nissan fan clutch.

Dal Locke
Email: [email protected]