Somebody please Help me!!!!!! i dont know what to do!

[highintheskyy]

i have a 1995 nissan 240sx if 86,000 miles. It ran perfectly up until about 2 weeks ago. The cars rpms would drop quickly which would make the car shake. This happens mainly in low gears and sitting in idle and it hardly happens when the cars in park. the engine just shakes as the rpms go up and down, and ill give it gas and will will do the same shaking until i give it alote of gas and pick up speed and it goes away. When i hit high speeds or even anything above 40 mph it kinda goes away.

When i first noticed this i changed my oil, filter, and spark plugs. My friend recommended i change my O2 sensor. But the problem persisted. So i read about the ecu and how to read the codes form the articles on this page, and it read out the number 34, which is a knock sensor, so i wasted no time, i bought the knock sensor and had it proffessionally put in......still mycar shakes violently at idle and low speeds. I checked my transmission fluid, oil, i even tried a new plug in each cyclinder. I dont know what to do.....?!!??!?! I recently checked my ecu again and it read out a 33, 34, and 37 in mode II. which means front O2 sensor, knock sensor, and closed loop. (what does closed loop mean? i changed the other 2 already.) then in mode I im getting a solid red light when i turn the car on, which the article on this site says if i get a solid read light that either my crank angle sensor or ECU is bad. I dont know what to do..if anyone can make any sense of my situation, please help me...any advice will be well taken and attempted.

[NISTECH]

Dont go buy an ECU thats not your problem. Closed loop means the O2 is not giong into cycle mode. In mode 1 of your 5 mode system you are looking at o2 operation. A solid red light means you are stuck rich or lean.

By your description of your problem it sounds as if your idle up isnt working. Pretty common to have problems with the aac/iacv on these. This controls your idle and bumps it up under load. When you are at idle turn on your high beams ,a/c system on full blower speed and turn your wheel to the right or left to its stop point and hold it. Does your idle compensate for the added load? OR does it fall off and stall or almost stall? If so you IACV needs a cleaning or replacement.

[rogoman]

Also check for a sticking EGR valve. With the motor shut off, manually move the EGR up and down to make sure it freely moves.