Car starts, stays idle, then RPMs drop and car shuts off

[dabears_23]

So I just bought a 1998 Nissan Maxima SE the other day, car ran great, engine had great pickup and the automatic transmission shifted excellent. However the old owner did tell me that the vehicle did need a knock sensor. I didnt think it was a major problem so I bought the car, i've driven it around for about 5 days and yesterday the car began giving me problems.

Yesterday I was driving up a bridge and the car began stalling, the RPMs wouldnt exceed and it was stuck in the 4th gear. The car had less than 1/4 tank but above the E. I finished going up the bridge and as I was coming down the car finally shifted and I went to pump some gas and I continued driving. Later that day, maybe a few hours later the car again began giving me problems. The car would accelerate very sluggish and then again it would reach a point where the RPMs wouldnt go any higher and then the car just died in the middle of the road. I wasn't too far from home so I kept turning it on and then driving, maybe about a half a block to 1 block until it would just die. I got home parked the car and called it a day since it was raining. This morning I go to the car, turn it on, engine is idle and then after maybe 30 seconds the RPMs go down and the car dies, no driving no pressing the gas no stereo just the engine on, and then it dies. Even when I turn it on and pump the gas it still dies. I even put some "Lucas Transmission Fluid" that helps cars with funky responding trannys.

-There is less than 1/4 tank of gas but right above the E.
-On Day 3 as I was warming up the car, with engine idle the RPMs would rise and then go down, every 10 seconds or so as if I was pumping the gas pedal. This appeared occasionally afterward too, but not every time the engine was idle.

Could it be the KS? Maybe a gas issue? Transmission Problem? Any Help is highly appreciated. Thanks for reading.

[loystock]

Unless you have a maintenance history of that car, it would be better to replace all the fluids.

KS problem will result in sluggish acceleration (due to ignition retard) but should not cause any problem at idle. Unfortunately, the KS problem will only store a fault code (e.g., P0325) but will not turn on the CEL. Your best bet is to have a free scan from Autozone and the likes and get a printout of the trouble code(s). This way, we can be systematic in the diagnosis. A YouTube video on KS replacement is available, courtesy of "boredmder."

http://www.youtube.com/watch?v=R2ntaxi7bXk
http://www.youtube.com/watch?v=fPIMOIwL ... re=related

Check and clean air intake components - air filter (replace as required), clean MAF sensor (CRC MAF Sensor cleaner will do, @ $8 from Autozone) and throttle Body (use a rag, do not spray carb cleaner directly into the throttle body). You may also have a problem with the IACV (Idle Air control Valve, servicing procedure available from the FAQ 'sticky' within this forum).

You may have a problem with the fuel delivery. You can start by checking/replacing the fuel filter (located on the firewall adjacent to brake booster). Ensure the fuel line is empty before disconnecting the fuel filter - FIRE HAZARD. With the engine running, pull the fuel pump fuse until the engine dies. Crank i a couple of time to ensure line is empty. Re-install the fuse.

It would be better if you have access to a fuel pressure gauge. You can make a T-fitting between the fuel filter and the fuel rail. With engine running, pressure should be @ 34 PSI. With Ignition ON but engine OFF, pressure should be @ 43 PSI (limited to 5 seconds operation). You can also check the leak-down after the fuel pump shuts off (pressure should not drop abruptly).

As for the transmission, I only use LubeGard Red (not black) ATF Protectant, but only after fluid replacement. It would be better to do a pan drop, clean the pan and magnets and check/replace filter - your call. You can have the transmission flushed or you can do multiple drain and refill ( Check/set fluid level while engine is warm and running. Run engine for @ 100 seconds then drain ATF immediately. Repeat this 2-3 times until fluid in the system is like new (pinkish red). You may need @ 15 quarts of ATF. Recommended fluid is Nissan Matic-D but Dexron III or the newer and better Dexron VI should work. Or you can go for the more expensive fluid from Mobil, Amsoil, etc.

[maxhopper]

I would think it's either a fuel issue or the MAF sensor.

If when the car acts up, the rpms do not go over 2000rpm, the computer is registering a MAF malfunction, and putting the engine in safe mode (but that should register a check engine light). If that is the case, check the electrical connection to the MAF and make sure it is seated fully and that the wires are in good condition. If those check out ok, you probably need a new MAF sensor.

But by all means, put more fuel in the tank and see if that's the problem first.

[NutriaforBreakfast]

ditto per maxhopper97-sounds like MAF