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Q: Engine light and VTM-4 light coming on - rough idle on 2005 Acura MDX

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Check engine showing codes P0172 and/or P0172-P and VTM-4 light coming on. Sometimes may go away for weeks when cleared, other times comes back fairly quickly. Have 105,000km (65,000mi) on the vehicle.
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Hey, we have an 04 Acura MDX and ours is doing the exact same thing. Did you ever figure out what the problem was for your vehicle?? We have been to 3 different mechanics and no one can find the problem. The article that the other person posted had a lot of useful information but suggested about 15 different things that could be the issue, just wondering if you had any luck yet. Thanks!
Yes - I finally tracked down the issue. The exhaust valves were tight. I got this suggestion from both an Acura service center as well as a Honda service center.

I guess this is fairly common on the Acura and Honda vehicles with the 3.5L engine. It isn't supposed to need to be adjusted until 160,000km, but they found many need it around 100,000 km.

I adjusted them myself and found that even though they were supposed to be .013 that I couldn't even get a .002 feeler gauge in. The intake valves were just fine (0.009). In Canada, the Acura dealer would have adjusted the valves for $529 and the Honda dealer quoted me $550 once and $299 a different time. Unless you are mechanically inclined I wouldn't recommend doing it yourself. It took me about 8 hours. I could do it in about 4.5 hours the next time. I also have the service manual to go from.
Not this reply above that I tracked it down was from me, the original poster. I just didn't log in first.
Been chasing this issue forever, and tried everything. Tuneup, throttle body cleanup, EGR check, etc. It all came down to valve adjustment. Car runs like new now, dead quiet at idle, more power and improved MPG. It fixed everything. I had a shop here in San Diego do the adjustment, left overnight to make sure it was cold when adjusted 858-558-8808 a guy named Larry helped me out.
Glad I was able to help. I hope many others come across this common problem for this vehicle and often uncommonly known solution.
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