[Jpo805]

Hello all,

My friend recently picked up a 2004 Acura MDX with about 186k on the clock.

Got the car and it wouldn't drive above 65ish without misfiring. Took the intake apart cleaned the EGR ports since they were clogged with carbon, replaced EGR Valve and replaced all the spark plugs since they were fouled up. Car has been running fine since, but just yesterday it misfires on a cold startup then runs fine. After it warms up the rough idle is gone and it only seemed to misfire on startup. Codes on the vehicle were P0300, P0301, P0302, P0303, P0304, P0305, P0306.

Any ideas what this could be? As far as I know the 2004 models don't have the idle air control valve.

Any help is appreciated trying to get this issue rectified.

 

[habbyguy]

If it's never had the valves adjusted, chances are that's the problem. The suggested interval is 100K miles, and they really DO get tight and start causing misfires. Worse, if you ignore it long enough, it'll start damaging stuff and the problem goes from something you can do for no money and a few hours to a big investment in a new or rebuilt motor.

 

[Jpo805]

If it's never had the valves adjusted, chances are that's the problem. The suggested interval is 100K miles, and they really DO get tight and start causing misfires. Worse, if you ignore it long enough, it'll start damaging stuff and the problem goes from something you can do for no money and a few hours to a big investment in a new or rebuilt motor.

Would needing the valves adjusted only cause misfires on startup? I was thinking that but I thought it would misfire all the time.

 

[forbin404]

I had the same problem, when you see multiple misfires it's either a valve job ($300 Non Dealer/ $1800 dealer) or a new coil pack.

But 186k it really points to valve job. Honda's have to have that every 100k (like a timing belt change) regularly.


BTW has the timing belt been changed?

 

[Jpo805]

I had the same problem, when you see multiple misfires it's either a valve job ($300 Non Dealer/ $1800 dealer) or a new coil pack.

But 186k it really points to valve job. Honda's have to have that every 100k (like a timing belt change) regularly.


BTW has the timing belt been changed?

That's what I was thinking. Timing belt service was done at an Acura dealer at 95k miles. It says the valve cover gaskets were change as well on the Carfax, but I'm unsure if the valves were done.

Don't think it's a coil pack cause the misfire goes away when the car is warmed up or driving, and it's misfiring on all cylinders.

 

[forbin404]

Well there are 4 things

1) Bad Plugs
2) Bad EGR Valve
3) Bad Coil Pack
4) Valves out of alignment.

Sounds like you need a valve job.

 

[LeftOverParts]

Your throttle body could be part of the problem if the throat has build up and restricting air flow past the plate. Loosen and move the intake duct out of the way and use throttle body cleaner on a rag to clean the throat. Pivot the throttle plate with the handle of a screw driver so you have access to the top and bottom of throat. Watch out to not get your fingers pinched. If you take the throttle body off, you have to reset the PCM. Search this forum on how to. To erase the codes, you can do the same reset.

Is your idle speed around 1000-1200 rpm when cold or staying around 750? It should high idle when cold.

You can search this forum for cleaning/checking the MAP and IAT. I have an 06 with just a MAP and IAT sensor but I recall through 04 or 05, the IAT system is a little different. (Coolant temp is also an input to the PCM.)

Let us know what you find out.

 

[habbyguy]

Also, I forgot to mention the PCV valve - it's probably not the issue, but it's dead easy and cheap to swap out, just in case. I agree also that misfires on multiple cylinders are almost never caused by (the amazingly reliable) Honda coil packs. On ONE cylinder, maybe... but not most of 'em.

 

[Jpo805]

Your throttle body could be part of the problem if the throat has build up and restricting air flow past the plate. Loosen and move the intake duct out of the way and use throttle body cleaner on a rag to clean the throat. Pivot the throttle plate with the handle of a screw driver so you have access to the top and bottom of throat. Watch out to not get your fingers pinched. If you take the throttle body off, you have to reset the PCM. Search this forum on how to. To erase the codes, you can do the same reset.

Is your idle speed around 1000-1200 rpm when cold or staying around 750? It should high idle when cold.

You can search this forum for cleaning/checking the MAP and IAT. I have an 06 with just a MAP and IAT sensor but I recall through 04 or 05, the IAT system is a little different. (Coolant temp is also an input to the PCM.)

Let us know what you find out.

Haven't got a chance to do anything else, but started the car today when cold, and idle was very rough around 750, then jumped to 1000 and started misfiring. Once it started warming up the misfire went away.

Maybe as you said some ports in the throttle body are clogged and airflow is being restricted.

Also I was thinking the PCV valve and will be replacing it since it's cheap enough to replace.

 

[LeftOverParts]

Like forbin and habby mentions, you might want to check your valve adjustment. I recently had a similar problem and their posts about the adjustment helped me. I was surprised at how much the clearances on my 06 changed between 83K first adjustment and 141K. The front valve cover is easy to remove to check cyls 4, 5, 6. Checking those could give you an indication of what the rear bank might be.

Also, re my earlier post that the 04/05 IAT system might be different. The 04 IAT sensor is in the intake duct ahead of the throttle body. If you remove the MAP or IAT, to check/clean them, you might need to replace the o-ring.

Just to ask the obvious and mention other low cost checks, did you check the air filter, use good premium gas like Shell, Mobil, or Chevron? I realize you mentioned it's only rough when cold but a $7 can of Seafoam in the gas might help, wouldn't hurt in case it's injector related. Saying this because of your original post about having fouled plugs - black carbon or wet oily?

In case it helps, just started my 06 cold and it immediately revd up to about 1100 RPM on the dash tach.

 

[Jpo805]

At this mileage I agree, having the valves checked is probably a good idea. Probably gonna have that done in the next few days since the car isn't being driven as of now.

Air filter is clean and newer, and good premium gas is being used. The plugs were fouled with black carbon not wet oily. Unsure of the type of gas the previous owner used.

Hopefully I'll be able to check the IAT sensor and Map sensor today