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Discussion Starter #1
Wow, it's been a long time since I posted a new topic! I used to spend more time here before starting our family.

Sorry this is long and a lot of information.

2004 Touring purchased new March 2004. 188,500 miles.

Got the infamous P0301-306 and PO300 with VTM4 light. After warm and reaching closed loop you can restart and VTM4 light goes out restoring AWD.

No, I haven't done the valve adjustment...YET. I'm not 100% sold on it and want to make damn sure I've checked all the basics out first. Yes I've seen all the posts claiming miracles from that. :wink:

A few things I've done:

EGR pipe clean down to valve. No ant farm on the plenum plate. I did not remove the intake. It's unclear to me if there are ports on the bottom of the 04 intake? In any event not much carbon to speak of. Clear gasket holes and intake holes. I ended up replacing the EGR valve and gasket. I had cleaned it and then it made a horrible whistling noise - possibly when I screwed up the "gasket".

I did notice a slight twist of that center flexible gasket under the plate, but I believe I straightened it out. It must have come that way from the factory. Nobody else would have been in there.

Replaced the PCV hose. It collapsed by the intake nipple. Seemed to be allowing air through but for $6 worth the replacement. Replaced the valve too. I couldn't hear the pintle rattle. Did notice some gasoline smell on my hands from that. I don't smell anything under the oil cap.

Replaced the PS pump O rings and changed some of the fluid. Most certainly is unrelated but the lights turned off completely for a day after I replaced them. At least now the pump is quiet and not overflowing. LOL!

Checked for current from coils. Haven't found the spec for coil test yet but they seem to be consistent. Replaced plugs with OE NGK in October. Double-checked the gap. Had some cheapies in there for a while. Yeah, I won't do that again.

Engine compartment seems really dirty, especially on the battery. I'm not hearing a leak anywhere but maybe I'm missing it. Is there a common place to check? I have a good seal on the air filter and I changed it last summer. But compared to my Accord with 120k there's a good buildup of grime over there. Just realized I've probably not even changed that air filter. :surprise:

Yesterday I noticed that the radiator fans weren't coming on. Temp was around 55F. I went for a drive and still nothing. I unplugged the fan connector from the CTS and they turn on. Also confirmed that the compressor kicks them on and then also switched the relays around in the fuse box. Doesn't make a difference. The car has never overheated or moved past a little bit less than halfway on the gauge. I would certainly expect the fans to come on. My Accord V6 does even in winter. Granted it's a tighter engine compartment but I would still expect them to come on after 20 minutes.

Also suspicious of the thermostat. I don't think it was changed when my guy did the timing belt/water pump service around 120k - maybe 3 years ago. Radiator cap is lukewarm at best.

My FIL is dismissing the thermostat as an issue. I'm thinking of ignoring his advice and just picking up the OE thermostat plus seal/o-ring. Can I do the change without losing a bunch of coolant? I'll probably pick up an extra bottle just in case. I can always use it on my other Honda.

Also need the cold/hot specs for the CTS. I have the dealer 03-04 MDX service manual that I bought from Tim quite a while ago but it's either not in there or I'm looking in the wrong place.

The ride is still pretty good and the engine quiet for how old she is. It's the wife's car and I'm thinking we'll get her something new and then I'll ditch my Accord for the MDX for better snow driving if we can work through this.
 

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I doubt that the thermostat is bad - they rarely really fail. It's not an expensive part though, and not hard to change, so there's no great cost associated with taking a shot at an improvement in the engine temperature. FWIW, my fans run very little, other than in the AZ summer with the A/C on (when they're on pretty much all the time, of course).

If the vehicle hasn't had a valve adjustment done in 188,000 miles, do it whether it's causing "problems" or not - you really don't want to let that go until you start causing real problem$ due to too-tight valves. The misfire codes are most likely (95%?) your engine telling you that it's past time to do the valve adjustment. If you had the intake off, you were about half-way to where you need to be to do a valve job anyway... it's not all that tough a DIY, and is well worth it. Chances are it'll cure your misfire, and give you a smoother-running, more efficient engine to boot.
 

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Discussion Starter #3
Well it's not the valves. First time doing that. I took the less is more approach. Maybe the engine runs slightly smoother...or it's in my head. Lights are still on. Just got a code on my Accord for the first time tonight. I hate to say it but I think I'm working my way out of Honda.
 

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Discussion Starter #5
Yes, just the battery disconnect method. They were gone for a couple of long commutes (what's the technical term? Global something or other) and then came back.

Since I neglected my Accord air filter for the last 6 2/3 years I checked the MDX and it's clean as a whistle!? I've probably had that filter 12-18 months. Clearly there is a vacuum leak somewhere that I haven't found...yet.

I had a PO3497 on the rear cylinder bank come up on my Accord the other night on my way home from work. Not only is the air filter horribly gross but one of the fine hair electrodes on plug 2 is destroyed and the insulator chipped. After pulling the codes, cleaning the air filter a bit, and reinstalling the plug - the code cleared itself. New plugs should be arriving today or tomorrow and the new air filter will be installed when I do the plugs. But damn, these V6 engines usually behave more like my Accord.

You might say to yourself "why the hell can't he maintain his vehicles better?" I usually do. Oil and ATF are always done at the intervals. Life goes on...
 

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With new plugs, a valve adjustment, and a new PCV valve and EGR valve, you've hit most of the common culprits. You could have a bad fuel filter or fuel pump (does the car hesitate at full throttle?) or maybe bad O2 sensors (logically, two of 'em would have to be bad to generate codes on all six cylinders).
 

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The preferred way to diagnose misfire codes is to look at freeze frame data with a scan tool. That gives exact conditions when the MIL was set. Do it few times to see if there is a consistent pattern, and you can rule out quite a few possibilities and focus on the most likely ones.

Looking at fuel trim values will give you a clear indication of a vacuum leak, low fuel pressure, blocked injectors, etc.
 

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Discussion Starter #8
Well I never did figure this out. When I took it in for the passenger side airbag inflator recall, the service writer said don?t bother with the valve service. Start with the MAP sensor. I was also going to order a new radiator. I couldn?t figure out where the coolant smell was coming from for the longest time but it was a tiny area at the top that could hardly be seen. I would have changed the thermostat when I did it.

All of this is academic now because my wife rear ended someone who stopped suddenly and it?s totalled just shy of 200k ? We are somewhat heartbroken as it?s the first car we bought together and the car we used to bring both kids home for the first time. On to a new MDX, Pilot or Highlander.
 

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Discussion Starter #10
Looks like it?s going to be a Pilot. Couldn?t get it done today as my wife needed to get some medical stuff done due to the crash. It?s been an ugly 10 days. My Accord got sideswiped on the freeway by a huge lifted pickup. It?s repairable but we found out yesterday that I likely have a concussion.
 

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I had this on a 2005mdx

I bought an MDX with these code
new wires and plugs
All valves adjusted.
My mechanic had to clean out the intake manifold and clean the injectors.
Then the 30x codes went away.
 
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