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I have 2001 MDX w/162,500 miles. I'm original owner. I see these same issues in other threads here. Had issues on/off for the past 2 years - Check Engine and Vtm-4 lights come on and 4WD doesn't work, car idles & runs a bit rough, and just in the past week something new - it stalled out 2x after the engine went from being under load to dropping to idle. Issues seem more likely to crop up when it's very cold outside. I've been putting Sea Foam in the gas since the problem started every 3-4 months and it helps the problem go away - for a while. My mechanic pulled the following codes P0700,P0303,P0304,P1740 (auto trans fault, cyl 3 misfire, cyl 4 misfire, problem with 4th gear clutch pressure switch circuit) but they are not Acura specialists and don't have clear idea what to do. I've seen advice on this forum including valve adjustment, replace EGR valve, replace VTM temp. sensor. SEEMS LIKE VALVE ADJUST IS THE MOST OFTEN RECOMMENDED COURSE OF ACTION. Wonder if you guys who are tech savy could point me in the right direction. Thanks.
 

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What preventative maintenance have you had done, in those 162K miles? Timing belt, valve adjustment are well overdue. Valve adjustment may be part of your issue, or it may not, but if you haven't had it done, then that is where I would start. Also have you ever had anything done regarding oil changes in the Trans and VTM, if not, you may be on the verge of bigger issues.

Helping us understand what maintenance you have done over the years will be a big help in helping you with your idling issues.
 

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Thanks for the response. Only maint. I haven't done is a valve adjustment. I've replaced trans and rear diff. fluid as recommended in owners manual. Did timing belt at 108,000 and spark plugs and water pump at that time as well. Reason I didn't have valve adjust done was that owner's manual said to do at 105K if making noise. It wasn't making noise.
 

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That's great news, well kinda. The valve adjustment is actually a very important thing. If the exhaust valves are tight, and they generally are, there won't be much noise, but the engine will run rough, and not pull in the correct fuel charge, for the next power stroke. Also it is fairly typical for these engines to make noise, but they are already so quiet, that that noise, really isn't all that noticeable, and since it occurs over time, most may not even know it is making the noise. I know this is the internet, and it is hard to diagnose symptoms over the web, but the valve adjustment is exactly where I would start with those miles and symptoms.
 

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Thanks CO MDX. What do you think about the EGR valve and VTM temperature sensor? You sound knowledgable, where did you acquire your knowledge? BTW - I used to live in Colorado, for 12 years in the 70's and 80's. Close friend lives in the Springs. My daughter lives in Boulder.
 

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Thanks for the response. Only maint. I haven't done is a valve adjustment. I've replaced trans and rear diff. fluid as recommended in owners manual. Did timing belt at 108,000 and spark plugs and water pump at that time as well. Reason I didn't have valve adjust done was that owner's manual said to do at 105K if making noise. It wasn't making noise.
Valves will make noise only if the valve clearance is too loose. On all the MDX I have owned, the valve clearances are always too tight when they need adjustments, that's why they won't make noise.
 

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Thanks CO MDX. What do you think about the EGR valve and VTM temperature sensor? You sound knowledgable, where did you acquire your knowledge? BTW - I used to live in Colorado, for 12 years in the 70's and 80's. Close friend lives in the Springs. My daughter lives in Boulder.
Knowledgeable??? Well, I am by no means an expert, not at all. I have about 6 years of wrenching on the venerable Honda 3.5L V-6, in the RL, three Odysseys, and now the MDX, which I have owned for a couple of months. I have been wrenching on vehicles and tractors, as the original farm boy, since I was....well I can't remember, but I completely rebuilt an antique tractor for the 4-H fair when I was 10, and no my dad didn't do the work for me. Now I am staring 40 in the face this year, so for at least 30 years I guess, still I do not know everything, but I tend to know where to go to get the right info. I find myself reading technical documents as a hobby so to speak, and I am a firm believer in factory service manuals, over the Haynes, or Chilton ones. I do all of the work I can myself, I do not take anything to the dealer because I have to, but now more than ever, because I just don't have the time. I have done these valve adjustments, and other major engine and trans work, I am not afraid of anything on a Honda. I am an Electronics Technician by training, and have fixed more Electrical gremlins in vehicles than I care to count. So there you have it, I work on a lot of my own vehicles, but I have never been formally trained, or worked for any automobile service institution. So always please, listen to others as well, I am no expert.

More to your specific vehicle questions, EGR, is it possible absolutely, but EGRs get plugged all the time, and don't throw misfire codes, at least in my limited Honda Experience, but again, I am no expert. I really lean on the valve adjustment because it is very very common from what I have read, and my own experiences that the exhaust valves run tight as they wear, and in every case, where they were allowed to run tight, due to not adjusting them on time, the engine exhibits your misfire symptoms. While it is entirely possible this isn't your problem, it needs to be done regardless, therefore if we are just throwing parts at it, this is the first I would try.

Sorry I forgot about the Colorado questions...I have lived in the Springs since '06, and LOVE IT, I currently work in Denver during the week. I bet you wish you were back, the Springs, has to be one of the best places to live, if you enjoy small town outdoors.
 

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Discussion Starter #8
Thanks for that info CO MDX. Anyone know why if it's a valve issue the 4WD system is affected?
 

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Thanks for that info CO MDX. Anyone know why if it's a valve issue the 4WD system is affected?
Not just a valve issue. The VTM-4 would light up if any issue arises with the powertrain. Since the engine is part of the powertrain, the VTM-4 will light up if there is a problem with the engine. Fix the engine problem and the VTM-4 light will go away, provided that you didn't have any other problems with other components of the powertrain such as the transmission or the rear differential.
 

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Reason I didn't have valve adjust done was that owner's manual said to do at 105K if making noise. It wasn't making noise.
That's not what it says. You're misinterpreting the chart on page 252 in the owner's manual, pictured below. It says to adjust the valves BEFORE 105K (at 7.5K, 15K, 30K, etc up to 90K) only if they're noisy. Otherwise, they should be done on schedule at 105K miles - REGARDLESS of whether or not they're noisy. Your valves are now 57,000 miles overdue for adjustment. No wonder you're experiencing problems!

 

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Discussion Starter #12
I had the valves adjusted and spark plugs replaced on my 2001 MDX about 4 weeks ago. Seems like the valve adjustment has done the trick as far as the engine problems go - knock on wood. Check engine and VTM-4 lights have not come on since, the car has not cut out during idle, and the engine is running much smoother at idle. thanks to those that helped steer me in the right direction.
 

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similar situation for me... no valve adjustment or timing belt up to 163,000 miles on my 02. Had situation where during cold winter.. cel and vtm4 came on a few times but went off. Had an exhaust leak fixed and bang, misfires on all cylinders and 02 sensor codes with cel and vtm 4 on all the time.

Changed plugs no change, had valve adjustment - got rid of misfires, invested in timing belt and just had front o2 sensor done today.. woo hoooo. cel and vtm 4 lights are off...

after not visting this site in many many years, the guidance and advice from those on this site has been priceless...

thanks all.
 

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Discussion Starter #15
Fast forward 4 years from when I started this thread. Still have my 2001 MDX. Now has 206,000 miles and has been having some issues of late that mimic some of the same that prompted me to start this discussion 4 years ago - CEL & VTM-4 lights coming on sporadically, rough running, engine shutting off. Plus there have been some other issues that are hard to explain. NAV display has been on the fritz for past 2-3 years - started with pixels changing color, then periods where it would blank out for day or 2, then longer periods where it would go dark - longest being 6 months from this past April to October. I had written it off and then we had an unseasonable cold snap here in Colorado a few weeks ago and the screen lit back up, but it would go dark once the car got warm or the ambient air temp outside rose above freezing. Colder temps seem to correlate somehow negatively with the rough running problems - in past week the car has shut off 2X while running in cruise mode on the interstate, and it took me several minutes to restart - pretty unnerving. And cold correlates positively with the NAV display working again. Seems like there may be some sort of electrical issue having to do with temperature changes - circuit board connections expanding/contracting? But are the engine issues somehow related to this as well or is that separate? Another valve adjustment necessary, even if it's only been 40 K miles since the last one in 2015? Hoping that some or all of you that helped me solve the problem back in 2015 can weigh in on this and steer me in the right direction again.
 

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Discussion Starter #16
Thank You for the feedback, and glad to hear your vehicle is running as it should.
Thank You for the feedback, and glad to hear your vehicle is running as it should.
Hi CO MDX. You were really helpful 4 years ago! If you have time look at the post I added to end of this thread today. I'm back in Colorado now and having some similar issues with my car. Hope you can help! thanks!
 

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First - your nav does seem to have some sort of thermally-induced intermittent. The problem is that it could be one of literally thousands of "things" (if you include the components on the circuit board). A plug that's not properly seated can cause your nav system to act like it is, if you're lucky (since you can troubleshoot this kind of problem by wiggling things around a bit - if it's a plug, you'll almost certainly see it acting up / acting right with some movement of the plugs). If not, then it's a problem with one of the modules. Being an electronics geek myownself, if it was mine I'd probably get a can of "freeze spray" (you can use a can of PC keyboard duster turned upside down) to spray on the suspect components, but this would be a lot of fiddly work. Still, it might be worthwhile to pull the display out and spray the bits you can get at easily - if that causes it to come on, then you know the problem is in the display (you could even try to figure out exactly which component it is with the freeze spray, but that's beyond most shade tree mechs).

Your engine problem - first, it's not because of valve adjustment - that won't kill the engine running down the road.

I'd see if there was any kind of code by using an OBD reader - sometimes there will be something that will point you in the right direction "in the system" even if the check engine light isn't on.

Next, I'd sincerely recommend spending a whopping $20 or so to get the Torque Pro app and a Bluetooth "dongle" that plugs into your car's OBD port. That works if you have a 'droid phone, but there are similar apps / dongles for other types. With that, you can monitor lots of really important parameters while you're driving along, and see which of them is going south when you are in "malfunction mode". In this case, I'd set up a "custom dashboard" that shows the fuel pressure, the throttle position, the vacuum, spark advance and coolant temperature, as well as battery voltage. Then keep an eye on it for fluctuations that don't look right - you might get some advance warning of your next flame-out. ;-)
 

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Just an FYI - here's the "virtual dashboard" I set up for my Audi on my Torque Pro app (there are some differences from the one I had set up for my MDX, as different vehicles have different sensors). You can get an idea of the kind of things you can monitor "just driving along". Mine includes altitude (GPS based), vacuum / boost, alternator volts, catalytic converter temperature, timing advance (good for seeing any effect of the fuel you're running), etc... I'm not in the car so you can't see the needles / values - but you can get the general idea.

113798
 

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Jumping in here because I'm having similar issues. Unlike mshegda, I have done very little maintenance on my 01 with 200k miles.

In fact, my issues began when I finally got the timing belt/water pump changed; my CEL and VTM-4 indicator came on shortly after leaving the shop.

I ignored it for 2 months/2.5k miles until I failed emissions last week and got a slew of codes. P0700, 0300, 0302-0306, and finally 1740. Thought it might have to do with the timing belt install, so I took it back to the shop.

Mechanic said it couldn't be the belt. He (somehow) came to the conclusion that a bad ignition coil was to blame. I had him replace three on the same side, although he said I could get away with just replacing one. CEL went off, ran smooth for a couple days. I passed emissions even.

Two days later, things went real south real fast. The CEL came on by itself in the morning. That evening I notice a strong exhaust smell in cab after running car idle for 10 mins, and it took a few tries of toggling between park and drive for the trans to engage.

I stop for gas that evening. I hit the gas pulling out and all of a sudden the car kinda lurches and the Rpms are jumping, VTM-4 light is on, CEL is blinking... Car feels worse than ever before. Drive about 10 miles home. Very little power, gurgling type noises... I'm legitimately worried my car is about to die.

Get a complimentary tow to the shop that did the belt/coils. They spend all day looking it over and say now ALL SIX coils are bad. From what the mechanic said, the catalytic converter is so clogged that the back pressure is causing the ignition coils to hit the spark plugs and hence misfire. All said and done, another $1800 job.

This guy missed the problem once before. Is he even close with his diagnosis now? He said the engine ran great when cat was bypassed. Not sure I'm buying the story and I certainly don't wanna burn more cash. I admittedly know next to nothing about cars.
 
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