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Discussion Starter · #1 ·
My 2004 Acura MDX has the following symptoms: check engine light plus the VTM-4 light (the VTM-4 light goes out after I shut down the car and restart). It runs a little rough at start-up, but then seems to run fine. The check engine light flashes during the time it is running roughly.

I have a ton of codes--misfires on all six cylinder (P0301-P0306) plus random misfire (P0300), plus pending codes for the same misfires, plus P2279 (intake air system leak)

The first shop I took it to wanted to replace an ignition coil and see where things stood. I had replaced one last year. With the engine running, I disconnected each of the six coil connectors, and each time the RPMs dipped, so that suggests that the coils are working.

Any thoughts on what the problem might be? I'm wondering if it's a valve job or something else. Of course, it could be more than one problem.

Thanks for any suggestions.
 

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How many miles? It's a given that over 100,000 miles the valves start to "tighten up" and need to be adjusted. Eventually misadjusted valves start throwing those P0300X codes and cause all sorts of other mischief.

That won't cause a P2279 error code though. Here's what the manual has to say about that code - some good advice about where to look, even if you don't have access to a HDS (Honda Diagnostic System) laptop.

 

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For the P03XX codes, probably a valve adjustment. If you have over 150k then you are due.

I have no idea on the air intake one, when my valves were bad I got random P03XX codes and the car kept getting worse (more codes) $300 later, it's fixed (Because it takes a while to adjust the values and remove and put back all the stuff.)
 

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Good thing you challenged your mechanic.

The valve adjustment is called out in the maintenance schedule for 105K miles. First adjustment on my 06 X was at 83K where all exhaust valves were out of spec tight (low) and again at 141K when all intakes were out and exhausts needed another adjustment. I was getting P0305 code on recent round.

Other items I checked were plugs and found two loose. I swapped plugs across cylinders and nothing changed.

Other causes could be PCV, throttle body, IAT sensor, MAP sensors, injectors, and fuel pump.

I diagnaosed a bad fuel pump last weekend for occasional stumbling and rough idle that was occurring when cold or after sitting for about an hour. I received the pump today and installed it. Looks like the problem is resolved and I'm going to update my post Sat morning.

A few fairly quick, low cost things you can try are checking the plugs for tightness (or pull out a couple in the front bank to see if they're fouled), add a can of Seafoam or Techron in the tank to see if cleaning your injectors helps (might help a little). Remove PCV and check if you feel movement.

For my stumbling problem, this week before getting the pump, I tried always putting the key to position II twice to pressurize the fuel line before starting and never got a stumble - which reinforced the diagnosis that the fuel pump was going bad. (Also,when I was testing the X last weekend and relieving the fuel pressure, it would stumble in a similar way except die of course.

If you haven't already, there's a lot of info on this forum if you search for rough idle, misfire, P0300, throttle body, etc.
 

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Discussion Starter · #5 ·
Wow--thanks so much for the suggestions. I took the PCV valve out, and it doesn't make any sound when I shake it, so I will swap a new one in, and then take it in for a valve adjustment, because it has about 165,000 miles and I have no idea if the previous owner ever did a valve adjustment. Thanks again.
 
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