[mmm_2000]

Here is a quick history of my car:
2000 sentra 1.8, AT, i have 82k miles on it

- replaced battery at 54k (that's when i purchased the car)
- replaced rack-pinion unit at 65k (leaking)
- replaced front pads and rotors at 70k
- replaced alternator just a few months ago at 80k (the diodes went bad as I got a "diode ripple" problem on a electrical tester)
- regular maintenance done by the manual
- I also have a K&N air filter installed and I serviced it regularly

So a few weeks, maybe up to 6 weeks ago I started to notice a problem with the idle and the problem is present since :

I am stopped at a light, car in "Drive" and I notice that my rpm goes from like 700 ( the regular rpm for that situation) down to like 300-400rpm just for like 3-4 seconds and I also feel some vibration coming from the engine and then it goes back to normal.

Then after exactly 30 seconds it does it again, but I only feel it when stopped and the engine is at idle or low rpm.

Its weird cause that variation in rpm comes every 30 seconds ! If I turn the AC on, the cycle is broken and it would not do it again until after a few minutes and then it starts again ! The same 30 secs !

This problem appears even when the car is in P (park) !
I spent about 1 hour in my garage examining the problem at idle !

Let me remind u that the car runs perfect otherwise.

And the problem only appears after the engine got to the normal operating temperature. Not when its cold.

In the manual it says I have to replace the spark plugs at 105k miles, so i have not replaced them yet !

There is no engine light or anything on while the car is running. Its just normal except that variation in rpm every 30 seconds.
And a few times while stopped at a light the rpm went so low that the engine died while the car was still in "drive". Then it started right back without any problem after cranking it. Cold starting is also perfect, I only have to crank it for like a second to start when the engine is cold.


Could it be a problem with the ignition coils ?? (it has one coil for each plug)
What could be the cause for that rpm drop ? Maybe the mass airflow sensor or some of the oxygen sensors (it has 4) ??
Should I ask a friend of mine to connect my car to a code reader ( He owns a repair shop), but there is no engine light or anything on. Is that code reader going to be able to pinpoint the problem ? i have not called him yet cause he is always very busy at the shop, but I will if I think he will be able to help me with that code reader.

Please help me cause I have a trip to Vegas coming up and I don't want to get stuck on the road !!!

Thank you