This is regarding the same 240SX that has the bucking like it has bad motor mounts. My check engine light comes on every once in a while, but then goes out while I am driving. The car runs no differently. Would the computer store the fault even though the light has gone out? So that afterwards I could check for trouble codes. With regards to the bucking, I have checked my throttle cable and it is adjusted fine. Do you think that the TPS may be causing the check engine and the bucking? How do I know if the TPS is in good shape?

Where is Menlo Park?This sometimes happens when winter comes, and the engine gets cold. Then once it heats up, it goes away. I park my 240 for the winter.The weather up here hit -25c today!

No, its not because of the cold. It was 21 Celsius here today. Menlo Park is in California about 50 km south of san Francisco

Yes to both. The ecm records and stores codes and the tps can cause bucking,hesitations and fluctuating idle if bad or out of adjustment. The check light sounds as if you may have a 02 sensor not shifting from lean to rich quick enough or just slow to respond. This also can cause mixture problems which affect performance.