RPM fluxuation at startup

[ilovebass]

hey i just got a 95 maxima, when i got it the engine light was on, everything seemed perfect, next day i checked out the engine light codes on the ecu(codes 0304, 0901, 0302). needs a Front Right Htd 02 sensor heater, knock sensor and maybe some egr cleaning. started it it up and the rpm went down past 300 then up to around 1500 and so forth then eventually started to level out at around 600 or so. anyone have any ideas why? mileage is 200 000 km btw

[RickDaTuner]

has it re-occurred since? you replaced those parts?

replacing MAFs and o2 sensor always requires your car to relearn the short fuel trim and the long fuel trim, these two things are stored in your PCM under the KAM, or keep alive memory.

If your condition was only present during the first few moments of start up then, this is just a sign of your PCM seeing the different readings from the new sensors and re-calibrating it self.

It sounds like your computer started in open loop, saw the huge change in values, when to closed loop, erased its data and then went back to open loop to re-learn the fuel trims.

If the problem is still present at this time, then it could be due a sticking IAC "idle Air control valve", a intake leak, or faulty EGR diaphragm, but its certainly not limited to these things rolling idle can be attributed to may factors.

A quick check for leaky intake gaskets is to take some computer dust spay stuff that comes in a can, and spray it around the intake gasket area while the car is running, while doing this, if the engine rpm suddenly declines and you feel the car almost stall, then its a sure sign of a leaking intake. the reason for this is that what ever propellant they use in those cans is not as combustible as straight gasoline mixed with air causing the engine to choke out when it draws the propellant through the leak.

hope that helps

[ilovebass]

i just got the car, i haven't touched it yet. thing is when i first got it it started up fine, now it has an idle problem, only thing ive done to the car since getting it is getting the codes from the ecu and reset the engine light.

[Jason Lange]

You need a new RPM fluxuation capacitor.