The problem with my Nissan Maxima

I have a 1997 Nissan Maxima and is idling very rough (check engine light is on). I replaced the fuel pump, 4 oxygen sensors, a cam position sensor, new spark plugs and the ignition coil on cylinder #6. I hate to spend more money on it since everything (like the ignition coil or fuel injectors) are very expensive without getting an idea that the problems will be resolved> BTW, I replace the MAF sensor also.
Ok….firstly, bummer. I’m not sure who guided you into thinking replacing parts haphazardly was going to repair the problem…but they should be avoided in the future.
The check engine light is on, this means the ECU is holding a code telling you exactly which item is causing a failure. You can get this code pulled for free…no joke, at just about any auto parts store. The code will give a description of the sensor it originated from, what the most likely cause is, and the repair(s)/parts necessary to clear it/fix your problem.
I don’t want to come down on you for replacing all those parts, it certainly didn’t hurt anything….but it was unnecessary for the most part. That light comes on for a reason, the computer stores a code for a reason. Even if the light goes off and the car acts up chances are the ECU is holding a malfunction code. It takes about 30 seconds to pull the code, this should point you in the right direction.
With shop and Maxima ownership experience I can pretty much guarantee you have an EGR failure. (Exhaust Gas Relief Valve) The valve is clogged or the solenoid that opens and closes it has failed. This is very common, particularly on your year Maxima. It’s a fairly inexpensive repair that can easily be done in your driveway. It may be something else but I’m 95% sure that’s what a good code scan will tell you.
Go get the codes pulled and go from there. Don’t buy any more parts until you’ve done so!! Autozone stores will do it for free no questions asked, others may ask you for a “deposit”…you take the auto scanner out to the parking lot, pull the codes, and take it back inside to get the “deposit” back.