So for a few weeks now my 2012 Quest [82K miles] has had a rough idle. The first time it happened I had been sitting at a particularly long traffic light when all of the sudden my engine started rumbling and shaking a little followed by the check engine light coming on. I took it to an auto parts store and had them check the code which came up as P0101 MAF/VAF Circuit Range/Perf Problem. After looking that up I found that that code could be for any number of things. The most common was the mass airflow sensor. I replaced that and though I think the engine is in general a little quieter [maybe just my imagination] it didn't fix the problem. The rough idle is not all the time but sporadic. It happens when in park or stopped idling. It seems to be a little worse when in gear. As soon as I take my foot off the break and give it even a drop of gas it stops instantly. I've noticed that when it happens the RMPs drop. It usually hovers between 700-1000 when idling but when it rumbles it drops to 350-500, the lower the move violent the shaking is. It usually only last a few seconds and then returns to normal. On my Father In-law's suggestion I tested for a vacuum seal leak by spraying them with WD40 while the engine was running to see if the engine sound changed if it sucked some in. I didn't notice anything like that. From what I have now read, it could be spark plugs, MAP sensor, O2 sensor in the exhaust, clogged fuel injector, etc. ect. If anyone can help me narrow down the possible culprit I would really appreciate it.

There is also another issue I am having that I will post on another thread. It seems unrelated but with computer controlled cars, who the hell knows. If you have the time please check that thread too.

 

Did you ever figure out the rough idle problem.