All,

I have a 07 Acura MDX Sport with 95,000 miles. Recently it started misfiring on a cold start and throwing a CEL (P0300,P0301,P0302,P0303,P0304,P0305,P0306) and SH-AWD lights, and It is still under power train warranty till 100k. I took it to the dealer and after a couple of days, and a few calls to Acura Tech Support they told me it needs a new ECU. So after replacing the ECU, I took the car back and I didn't make it to the first light, the misfire came back on so I took it back to them they had the car for about a week or so and made several calls to Acura Tech line and told me that they adjusted the valves, and did a Air Induction Cleaning and was not able to duplicate the problem. So I took the car back and was no able to get out of the Dealership the Nav Screen had the faulty message icon and the problem was back. I took it back to them and they kept the car again for another couple of days and said they adjusted the valves again and could not duplicate the problem. At this point Acura is just playing Trial and Error on the car. No one is sure what is causing it. This misfires happens on a cold start and the engine runs perfectly fine after it warms up. Today I started it up and I gave it some gas while misfiring, and white smoke started coming out of the exhaust pipes. I am an Acura, but I am starting to have second thoughts now because Acura has not been able to properly diagnose and fix the problem. Has anyone had this problem? If so how did you fix it? Any suggestions or Ideas???

 

I am an Acura Lover, but I am starting to have second thoughts now because Acura has not been able to properly diagnose and fix the problem. ***

 

Before my 10 MDX, I too had an 07 with around 120k miles. At around 105k miles, I had code p0420 (bank 1 catalytic converter performance below threshold) and because I am an auto electrician, I decided to find out what was going to cause the converter to fail. Come to find out, the ECM (when ambient temps were cold) was commanding EXCESSIVE lean air-fuel ratios for converter warm up purposes that were causing the failure. This is normal but not in excess. After more research, I also found it was a recall that was corrected by a module reprogramming that was to be done at the dealer...but my mileage was too high and not covered. My point here is the excessive lean AF ratio could be causing the misfires at startup so you may want to ask the dealer if its been done yet.

Also, have them or another shop check to see if there is carbon buildup in the intake manifold...an extremely common problem known for causing misfires at startup as well.

Good luck and don't give up. It will be something easy.