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Hello all,

I have a 2005 MDX 157,000 miles. For last 2 months i have been trying to diagnose the source of my cylinder 1 misfire(PO301).
I've noticed that when i leave the car outside over night and start it is when it misfires and sometimes the VTM-4 light comes on with it. If i shut off and restart the VTM-4 goes away.
Now yes i can garage the vehicle but if i leave it outside while im out i would hate to deal with this.
Here is a list of things I've done to help fix it,but was not successful.
1. Replaced spark plus, all 6
2. Replaced Coils, all 6
3. Replaced Fuel injectors, all 6
4. Replaced and cleaned intake manifold seals and throttle body etc.
5. Cleaned EGR and replaced seal
After replacing all the manifold seals and cleaning it. The check engine light didn't come on. Even after local trips and highway driving. But of course it popped up again and now i need HELP.
Thank you in advance fellow MDXers for help and reading this post.
 

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Not saying it is for sure but sounds like when I had a bad fuel pump. Here’s the post.


A couple of comments since it’s been awhile:

Before doing any fuel pressure tests, the main thing to observe is if it only misfires when cold or after sitting for a few hours. The key to position II several times might be helpful to diagnose this.

If you suspect the pump and decide to test for fuel pressure, I rigged up a special fuel test line. It’s also possible to just T into the fuel line with the loaner fuel pressure tester from autozone or Oreillys.

One alternate way to relieve the fuel pressure is you can unplug the pump at the pump hatch and start the engine and let it run until she dies. Then a couple more cranks.

Good luck!
 

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The first thing that jumps to mind - and fits the symptoms to a tee - is that you are well overdue for a valve adjustment. That will cause misfire, and will be different when it's cold than when it's warmed up a bit. The valves should be adjusted at around 100,000 miles, so if it hasn't been done, I'd expect there to be some misfires by now on your car.
 

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Not saying it is for sure but sounds like when I had a bad fuel pump. Here’s the post.


A couple of comments since it’s been awhile:

Before doing any fuel pressure tests, the main thing to observe is if it only misfires when cold or after sitting for a few hours. The key to position II several times might be helpful to diagnose this.

If you suspect the pump and decide to test for fuel pressure, I rigged up a special fuel test line. It’s also possible to just T into the fuel line with the loaner fuel pressure tester from autozone or Oreillys.

One alternate way to relieve the fuel pressure is you can unplug the pump at the pump hatch and start the engine and let it run until she dies. Then a couple more cranks.

Good luck!
The first thing that jumps to mind - and fits the symptoms to a tee - is that you are well overdue for a valve adjustment. That will cause misfire, and will be different when it's cold than when it's warmed up a bit. The valves should be adjusted at around 100,000 miles, so if it hasn't been done, I'd expect there to be some misfires by now on your car.
Not saying it is for sure but sounds like when I had a bad fuel pump. Here’s the post.


A couple of comments since it’s been awhile:

Before doing any fuel pressure tests, the main thing to observe is if it only misfires when cold or after sitting for a few hours. The key to position II several times might be helpful to diagnose this.

If you suspect the pump and decide to test for fuel pressure, I rigged up a special fuel test line. It’s also possible to just T into the fuel line with the loaner fuel pressure tester from autozone or Oreillys.

One alternate way to relieve the fuel pressure is you can unplug the pump at the pump hatch and start the engine and let it run until she dies. Then a couple more cranks.

Good luck!
Thank you for the advise. I have a friend who is a seasoned mechanic and they advised me to test the fuel pressure. Ill keep you updated.
 

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Discussion Starter #5
The first thing that jumps to mind - and fits the symptoms to a tee - is that you are well overdue for a valve adjustment. That will cause misfire, and will be different when it's cold than when it's warmed up a bit. The valves should be adjusted at around 100,000 miles, so if it hasn't been done, I'd expect there to be some misfires by now on your car.
Thank you for the reply. I hope its not that. Ive seem some videos online and it looks like a pain in the rear. Possibly my last options. Any link or videos to do this will be helpful. THANK YOU AGAIN!
 

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It's a fiddly job - no getting around it - but it's not "difficult" or beyond the scope of a backyard wrench-twister who has the ability to be at least a little careful. And of course, it's a lot better to go through the difficulty of a valve adjustment than to get to the point where your valve train gets damaged (not to mention the drop in gas mileage and power).
 

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it's a lot better to go through the difficulty of a valve adjustment than to get to the point where your valve train gets damaged (not to mention the drop in gas mileage and power).
I’m due for a valve adjustment (250k, bought it at 187k, unknown repair history, and getting misfires). I’ll need to have my mechanic handle it. Before I shell out for it, what are the symptoms of valve train damage and would that be too late for a valve adjustment to be worthwhile?
 

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Had the same problem as you!!! mine was at 257k and after the misfires went away (lasted less than a min when cold) the car ran fine and wouldn't come back for at least a month. One thing that'll happen on these if left for too long is the exhaust valves will start to get damaged you could do a compression test like i did before the adjustment and see if any of the exhaust valves are leaking, but they can still leak due to being out of adjustment and will go back if your lucky...My recommendation would be if the car is in otherwise good condition and you want to keep it do it sooner than later even after the adjustment one cylinder that had leakage from the exhaust valve #5 was still leaking. all the cylinders had around 200-210 for compression #5 was more around 110psi...even with the low compression on that cylinder it now runs like a new car it idles so smooth I kept forgetting it was even on and has no issues since and I've put 4k more on already I'm just gonna keep driving it because its still running so damn good. And i just drove it from MA-FL with no problems :) If one of your exhaust valves are too far gone after the adjustment it'll still misfire on that particular cylinder(s) and the engine will have to be taken apart to replace valves, seats etc.
 

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There aren't really any "symptoms" of valve damage that aren't the same as for misadjusted valves... well, until something is bad enough to cause mechanical noise - by then, it's way too late.
Chances are that the PO didn't do the valve adjustment (or maybe timing belt - there should be a sticker on the engine somewhere if it has been done). These are two jobs that really SHOULD be done to keep from "virtually totaling" the vehicle (particularly the TB). Just part of the cost of owning a Honda, really.
 

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.My recommendation would be if the car is in otherwise good condition and you want to keep it do it sooner than later
I definitely want to avoid those issues and it is in good shape, so i’ll have the valves done soon. I’m glad yours improved so much after that work. Thanks for the advice!
 
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