Join Date: Feb 2005
Location: Southern California
First of all, any mechanic who says the valves on the MDX are self-adjusting is just trying to BS you. These engines have overhead cams, not hydraulic lifters with push rods.
Second, I will tell you what happened to me last week when we bought a 2001 MDX with 156,900 miles. The car had been sitting there for a whole year because of some engine issues, but the body and interior are in perfect shape so I decided to fork out $4000 to buy it for my son who just graduated from college and is on his first job.
When the engine is cold, it will die as soon as I take the foot of the gas. Once warmed up it runs like crap but the engine would stay on except for an occasional stall at a red light. I remove the upper plenum and cleaned out the EGR passages, then put it back together, and the symptoms remain the same. Meanwhile the "check engine" light came on with the following codes 300, 302, 303, 304, 305 and 306, indicating misfires in cylinders 2 through 6, all randomly, of course.
Since we have another 2001 MDX, I swapped the IAC and the EGR between the two cars with no change at all; the symptoms remain exactly the same. Then I read online that bad valve clearances will do that to you, so I decided to adjust the valves myself even though the previous owner showed me a receipt for the valve adjustment done at an Acura dealer when the car went in for timing belt replacement at 103,000 miles.
Guess what I found! Cylinder number 1, the only one that is not misfiring, is the only one having any clearance at all on the exhaust valves. All the other cylinders had absolutely no clearance at all at the exhaust valves, meaning that those exhaust valves are probably close to being open 100% of the time. I re-adjust all the valves to spec (0.008"-0.009" intake, 0.011"-0.013" exhaust), clear the codes and put everything back together. The whole thing took me half a day.
Well, the car ran beautifully after that and the codes never came back. I ran it through the driving cycles to set the Readiness Codes and took it in for a smog check (so I can register the car in my son's name). It passed with flying color. Everything is like new. All it costs me are the gaskets for the valve covers and the intake plenum. About $90 total and a lot of my time.
By the way, when I open up the valve covers, the seals are so old and so stuck to the heads, and that led me to believe the dealer charged the previous owner for the valve adjustment job without actually doing it! Either that or they are really incompetent! I always thought you get better service at the dealers, but that didn't seem to be the case here.