I hope someone can help me out a bit. I've owned my Murano for over 7 years now. Recently, I've noticed a miss when the engine is cold. It goes away when it gets warm. I've also reset the MPG trip odometer and the gas mileage is in the single digits when cold but gets better when warm. It also has a bit of a surging or jerking motion when driving (again, only when cold). I'm in Sacramento, CA so the ambient temperature is always fairly warm. (Also, I believe it's unrelated but there's a coolant leak somewhere. I notice the stain in my driveway.)
I took it to one shop and he did a code-check (for free! but he was otherwise too busy to do the repair). There was no check engine light on but it came back with a P1800--VIAS Control Valve. It's a $20 simple-fix and so I replaced it but it didn't help. I then took it to another shop. They found no stored code. They kept it for a week as they were unable to reproduce the miss. I finally went there on a morning and had them listen to the miss. (It really was obvious to me and then them when I demonstrated it.
) They looked at it again and determined that it was the timing chain tensioner that was bad...the theory is that the chain has enough slack in it to cause the timing to get off and cause the bad gas mileage and miss. I'm not sure that makes much sense
I don't want to put in a lot of money into her at this point but if there's an easier fix, I'd like to do that before the cat converter is ruined by the rich fuel mixture.
All regular service performed (spark plugs, transmission fluid change, oil, etc.)
Any thoughts on what could be wrong? I'm thinking a sensor is likely, but without a code to go on, I don't know how to find which one. Is there a shop in the Sacramento area that is good with Muranos?