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Hi,
My 2005 Nissan Altima 2.5 L has cylinder 3 misfire (P0303 code) during idle. So far the following has been done:
1. Changed spark plugs, ignition coils and the injectors.
2. Changed the PCV valve and hose.
3. The Evap purge solenoid has been tested, there is no leak.
4. Upper intake manifold gasket was replaced when changing the injectors (Also loctited the butterfly screws).The car starts and drives fine without any issues. It even idles very smooth after a cold start when the RPM is high. After the engine warms up and idle drops to around 750, the misfire starts.
Especially in D and when the load is high (AC running). I am assuming its some kind vacuum leak as it drives very good.P.S.: I also checked the injector harness and the coil connected, they appear in good shape.
Any suggestions are greatly appreciated.
Thanks.
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Replies
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First have a look at your fuel trims and see if a vacuum coincides with the readings.
Many gasket vacuum leaks occur show up on a cold engine
Next suggest a compression test and perhaps a leak down test if needed..You mean if the vacuum drop coincides with the increase in STFT? What diagnostic information will it provide?
The LTFT on the car is 0 and the STFT oscillates between -4 %to 6% during idle.Thank you for your reply.
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