QuestionQUESTION: Hi Von,
I drive a Nissan Murano FWD '05 US SPec car in the Middle East(UAE). I would appreciate if you could please help me with your expert opions in the following issues.
1) RPM fluctuates when gas pedal is released (drops to 2 and goes up). this happens when the car is between 40-50mph. Recently i have changed the Spark plugs.
2) A hissing (missing) noise some where from the engine side. There is a dent in the muffler. Can it be the reason for the missing. Its really annoying and heard especially in the evening..as i feel drop in power also.
Hope to hear from you soon..
ANSWER: Raj,
Find the source of the vacuum leak and you will probably find the source of your problem. The engine monitors air flow and any vacuum leak will cause the issue you describe. If the muffler is not dented too badly, as in crushed, that would not cause the problem. Also, change the positive crankcase vent valve. rockauto.com or courtesyparts.com are both good sources for parts. If the muffler has a hole just weld it up.
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QUESTION: hi Von, thanks for the reply.. I would get the car checked for vaccum leak. I do the service @ every 3000Miles without any fail. Still do you find the need for replacement of PCV. Await your valuable advice.
ANSWER: Raj,
The positive crankcase vent valve is used to pull clean air into the engine and sweep the old out, through the PCV. Anyway, there is oil in the vapour and eventually it gets gummed up. If you remove yours and shake it and it clicks then it is fine. If not replace it. Other causes for strange idle are vacuum leaks, we already discussed. Next would be the idle air control valve, the throttle position sensor, you have drive by wire so you probably have an integrated unit. If this was bad the throttle stepper motor error code should make the check engine light come on. Lastly, the mass airflow sensor could be defective. This usually does not throw a code so you need adigital volt ohm meter to check it.
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QUESTION: Hi Von,
As advised I have taken the car to the dealer and they have told me there is no such issue with PCV and if there is probs with PCV the engine oil would be dark in color and in my car they could not find that. And d hissing noise is common in all Muranos'. When I took the car, the Service Engine Soon light was lit and it was bcoz of 2 error codes related to leakage of gas. They hv erased the codes and advised it would be okay now.I do not know what to do now..
AnswerRaj,
They are not addressing your vacuum leak. Now, I have some information that I can use to diagnose. Nissan had issues with rubber hoses used in the fuel emissions systems. The fuel system is closed and hoses allow the fuel vapour to go back to a charcoal canister. It is trapped there until you start the car and a valve opens allowing the engine to burn it off. Any leaks will set the check engine light. I would have them examine the system and find the leaky hose and replace it. Also, have them check all the clamps.
For the PCV they are not understanding what it does or how it operates. I described this to you. Just a purge filtering system for the engine oil so vapours do not vent to the atmosphere. It just makes a vehicle run rough when plugged.
