Do you have experience repairing NISSAN Altima’s?

I drive a Nissan 3.5 , it’s been hesitating when I push down on the gas pedal whether driving or in park. Won’t go over 70. At 70 it REALLY hesitates. I haven’t drove it since it started doin this but had to tonight - the exhaust just smells like straight up gasoline. I have 3 codes , p0650 twice, and p0420, I know 420 is a generic code. I checked removed and cleaned the mass air flow sensor and throttle body today , and air filter. Still does it. Haven’t done anything else. This moron at autozone recommended “cataclean” when I went to buy o2 sensors today.

Does anyone out there have any suggestions? I would like to get opinions before I take it to my mechanic. Since they are so expensive. I can do a tune up myself, or even replace and oxygen sensor. I want to get your opinion with this.

4 Answers

  • paul h
    Lv 7
    3 years ago
    Favorite Answer

    Year?...mileage? Hesitation or lag in throttle response is often due to a faulty TPS but can be other issues.It appears that the engine is running too rich which may also cause the lag/hesitation and can lead to clogging and destroying the catalytic converter. That is likely tripping the P0420 code but what is causing the running too rich is likely other issues. Some issues may not trip a trouble code such as a faulty coolant temp sensor (ECT) which can trick the PCM/computer into thinking the engine is cold when it is actually warmed up and causes the PCM to richen fuel mixtures improperly. A cold engine needs a slightly richer fuel mixture than a warmed up engine. But if the ECT readings are within acceptable parameters...just wrong for actual engine may not trip a trouble code and the PCM will continue adding too much fuel trim since it cannot know that the engine is warmed up and needs less fuel. Or the fuel system may have issues such as a clogged injector, faulty pressure regulator, etc.. causing a rich condition.

    The P0650 code indicates a problem with the MIL/Check Engine light circuit that may be preventing the warning light from coming on when the PCM detects a problem. A tech would need to test the related circuit for issues.

    It may be best to have a tech/shop run the car on a scan tool through a driving cycle from cold to warmed up and see when the codes pop up after clearing the system.That may pinpoint a trouble issue or show what systems may not be reading correctly such as a bad ECT. Check for proper fuel pressure and test the ECT for correct voltage values/readings for various engine operating conditions. If the converters are clogged up from running too rich for too long, they may need to be replaced or an effort to clean them. But you still need to find out what is causing the rich fuel trim condition.

    Perform a tune up if due, replace air/fuel filters, run some Seafoam or Techron in the fuel tank to clean injectors (they may need more thorough cleaning/testing).

  • Anonymous
    3 years ago

    You have a bad MAF sensor, a very common problem on this car. You must not buy an aftermarket unit, Nissan has updated it along with a software flash for the computer.

  • 3 years ago

    You are just making the same mistake as many have before. When a sensor throws up a code it is to say it is not getting a reading within what is needed to run the engine correctly. Whilst one possibility is that the sensor itself is faulty there are also many other possible reasons and the sensor may well be functioning well.

    Unless you can test the sensors and look at the other possibilities you will end up throwing good money after bad by replacing parts that are still functioning correctly.

    What Americans call a tune up is more commonly known around the world as a routine "Service" . It is unlikely to correct faults and would be done as a preventative measure not a reactive one.

  • Anonymous
    3 years ago

    P0420 : The cat converter has likely failed. What year and mileage is the car? It might still be under warranty. Call Nissan. Nothing wrong with your O2 sensors.

    P0650: There is a fault with the CEL circuit. This will require the diagnosis of a mechanic with a scanner.

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