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Discussion Starter · #1 ·
Let me start by accepting full responsibility for lack of proper maintenance on my 2004 MDX. Since purchasing this SUV a couple of years ago, we have had nothing but GREAT things to say about it. And even right now, as it sits on the lift in my shop, I still feel that my relationship with this MDX is not over. I am new to this forum and I have gathered a lot of information here so I thought that I would start my own thread and resurrect this MDX!!

As I am driving to the airport to start my vacation, my MDX with over 204,000 miles on it, shuts down in the middle of the freeway. All of the dash lights become illuminated as I coast to the shoulder. It would not crank over.
After enjoying my vacation and then trailer the MDX home, I start disassembly of the timing belt covers. I have changed timing belts on my other Honda's (before they broke) so I have knowledge of what to do. I also have Google..... and I was right, the timing belt was broken.

Being an optimistic, here is my plan, just to see if this motor is toast or salvageable; I will replace just the timing belt and if this MDX will start and run, then I will do a complete overhaul (new timing belt, water pump, tensioner, serpentine belt, plugs, wires, etc). I am not an auto mechanic, but I am very handy and can follow directions really well. So, I set both of the cams to the timing marks and then set the crank pulley to Top Dead Center and then I replaced the timing belt. With the plugs removed, I am able to turn the motor over (by hand) several times without any interference. Then, I replaced the plugs and I was able to turn the motor over with the key and it turns over without any interference or any noticeable obscure noise. I am excited!!!

But it still does not start. I remove the valve cover but see nothing that looks out of the ordinary. I turn the motor over (by hand) and all of the valves are functioning correctly. Of course all that I am seeing from with that cover off is the lifting of the valves. I replace the valve cover and remove a spark plug and find that there is no spark.

Could it be a module or sensor had gotten damaged or short-circuited during this ordeal?

Could there be a fuse that blows to prevent further damage when something this catastrophic happens?

What recommendations are there? What do I check next?
 

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The chances that the engine is not done for are 0.000000001% if it works alright you should probably run fast and get a super lotto ticket.

On the bright side you have a 1G MDX! and J35A3s are not super expensive so its still economically viable to get a new engine for her.
 

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Oh man, ouch! Asking the following because you didn't say. You set the timing of the cams and crank to TDC of no. 1 compression stroke, correct? I've only changed a broken timing belt on a Camry and after reset as mention above, it came back. However, pretty sure it was not an interference engine.

Are there any check engine codes? Other than these basic questions, I can't help much.

Just guessing - if you lucked out and the engine isn't damaged, the crank position (CKP) sensor might be fried or the PCM might need to relearn the CKP pattern. Sorry, I have no idea on how to test it or do the relearn. Not sure if the basic PCM/idle relearn via battery disconnect will do it.

Before you spend a bunch of time and/or money, you might consider a compression test to check the engine for damage. You can rent the tools from Autozone or O'Reillys.

In case needed, the picture attached from when I did my 06 X timing belt shows the sensor - it's the black waffled unit to the right of the crank pulley.

Maybe try searching the forum for a CKP test or CKP relearn.

Good luck - when you get it running, tell us how you did it.
 

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I wouldn't waste the time and money on that engine - it's probably just a door stop at this point. Yes, it would be possible to replace the heads (after making 100.000% certain no debris was left on top of the pistons, of course). I can't imagine a scenario where everything is flying around in the engine at 2,000 RPM (highway speed), and then comes to a stop without munching some valves. It's theoretically possible, but I can't imagine it happening in the real world.

FWIW, I just changed my timing belt - it had been done at 105,000 miles, and I swapped it at 220,000. I didn't expect to see a lot of wear, but the belt looked virtually new - no stress cracks or obvious wear anywhere. That isn't to say that I believe that the old belt was as good as new, but I figure that it's better to change it 50,000 miles early than 1 mile too late. ;-)

Good luck getting the car back together - I'd think that a boneyard engine would be the best option at this point. Not a huge expense, so there's little reason to spend the time and money on a real long-shot repair of the existing engine (IMHO).
 

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Discussion Starter · #7 ·
This is why I posted to this forum...... More info here than I have found on some YouTube videos. Time to get back out in the shop and test some of these things out.

No. 1 compression stroke? Not sure. I just lined them up and went for it. Like I mentioned, not a mechanic.

Barring something that would retard the spark or prevent the spark, wouldn't I still get a spark when turning the motor over?
 

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Can't do a compression check without a functioning drivetrain. I suppose you could kinda/sorta figure out if a particular cylinder is toast by (for example) rotating the crank to Cylinder 1 TDC, with the rear cylinder head rotated to having the Cylinder 1 valves closed (that would be with a "1" showing through the little peep hole on the side of the head). But rotating the engine to that point would most likely cause valve-to-cylinder contact. I'm guessing you could probably pull all the plugs and rotate the crank around slowly, stopping at every "internal bump" and then rotate the camshaft pulley until something else "bumped", and then just continue the exercise until everything was lined up. Then, with all the other plugs out, put in the #1 plug and see if you can easily rotate the crank. If you can, there's no compression (or in this case, vacuum - same basic problem). ;-) OTOH, even if you DO have difficulty turning the crank, that's only saying #1's valves might have survived. You could do the same process for #2-3, and then #4-6. Keep in mind you'll have to find a position on the cam pulleys that makes it possible to turn the crank without piston-to-valve interference (I'm guessing - but only guessing - there may well be a position that allows that). Turning the crank over with the plugs out will make it very easy to feel internal contact. You won't necessarily know if you're compressing each piston or trying to draw a vacuum, but you shouldn't have to turn it very far before you'll know if the valves are holding any kind of pressure (negative or positive) at all.

My guess - as entertaining as the above might be, it's probably a waste of time. I suppose you could toss in a new timing belt just for giggles, since at least some of the work you'll have to do is also necessary when replacing an engine (like the passenger side motor mount, power steering pump, etc.). Sadly, I just threw one away that was clearly OK for a lot more miles, or I would be happy to send it to you. But like most of us have mentioned - I really can't imagine a scenario where something didn't get munched inside your motor.

But keep us posted - it would be VERY good to know if there is ANY chance that a Honda 3.5 could survive a highway speed timing belt departure. ;-)
 

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This is why I posted to this forum...... More info here than I have found on some YouTube videos. Time to get back out in the shop and test some of these things out.

No. 1 compression stroke? Not sure. I just lined them up and went for it. Like I mentioned, not a mechanic.

Barring something that would retard the spark or prevent the spark, wouldn't I still get a spark when turning the motor over?
So you have a 50/50 chance of being right or wrong. I would check this before doing anything else.
 

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It might be easier if you google setting TDC no. 1 Acura V6 or the other posters might have a better explanation. You mentioned your not a mechanic so bear with me.

Also google the ckp and cam sensors.

Check for codes - see below.

Re TDC cylinder 1, compression, from you original post, you mentioned you already set TDC and already have your belt in place and can watch the valves move and feel no interference. It could be you have it correct. Or, worst case nothing might be hitting because the valves are bent out of the way. Let's stay optimistic and assume they are not bent.

So the place to start is to be sure you have TDC on no. 1 and the compression stroke. (You didn't say if you aligned to no. 1. You could have put TDC to another cylnder.)

OK, when you put the crank pulley at TDC, both cams should be lined up on the mark at 1. If this is correct, with the back valve cover off, all 4 valves in the back cylinder to the extreme passenger side (no. 1) should be all the way up. That means the valves are closed and the cylinder 1 is in compression, ready to fire. Another double check is that the rocker arms for no. 1 should be very slightly loose and have about 0.010 inch play (roughly 1/3 thickness of a credit card). You should be able to grab them and wiggle them very slightly up and down. You can compare no. 1 to the valves on the middle (no. 2) and right most cylinder (no. 3). Some should be high, some low. Some should not wiggle.

If no. 1 is not that way, you'll have to get it that way and the other posters are saying that you have to do that carefully, alternating turning the crank and cam pulleys slowly so you don't crash the valves and pistons together.

Close everything up.

If you haven't already, if there's an Autozone or OReilly nearby, see if they rent an OBD2 scanner and check for check engine light codes. Look them up if you find any.

After the scan and confirming TDC is correct, no promises but you could try a battery disconnect/reconnect to try and reset the pcm to try and reset the CKP position. Then try to fire it up.
 

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I should add since you have a 6 cylinder, TDC of compression should occur 6 times. So, you should be able to check where ever your crank and cams are at currently.

Suppose your cams are aligned at 3. if the.crank is at TDC, the valves should be high and and slight play should occur as described above on cylinder 3. This should be the case for all cylinders as you turn the crank and go around.

The cylinders are 1,2,3 across the back and 4,5.6 across the front. 4 is at the passenger side front.

When aligning, go slow and be meticulous to be sure the alignment of the marks are perfect.

Take care and good luck!
 

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OK, when you put the crank pulley at TDC, both cams should be lined up on the mark at 1.
Normally true - but with a broken timing belt, the crank and each cam are no longer flying in formation (kinda the whole problem). ;-)

That's why I suggested the kind of convoluted process for getting the rear cam and crank in a given position. The peep hole on the passenger side of each head will show you which cylinder currently has its valves closed (the cylinder number is visible through the peep hole for each cylinder). You will be flying blind on where the piston for each cylinder is, but you shouldn't have to turn the crank too far before the "selected cylinder" starts creating compression or tries to pull a vacuum (depending on whether you're moving the piston toward the head or away from it).

It occurs to me that it might make more sense to just pull the "front" head off the engine. If the engine's toast, no harm done. If it isn't, it's a great opportunity to set those valves sitting comfortably at a work bench. ;-) And there is some possibility that ONLY the valves are shot, or that you might be able to take the heads into a machine shop and have them repair the damage. Not a trivial undertaking, but I'd personally rather do that then swap an engine, even if the cost was the same.

Edit - I just remembered that the cylinder indexing (the little numbers visible through the hole) is all done on the front cam pulley - I really don't know if the rear cam pulley has a similar feature - if not, there's really no easy way to index the rear cylinders (1,2, and 3) to make sure the valves are shut, other than by putting both cams in their "alignment positions" (as shown with the A/B marks below) and tying them together with a timing belt, even if you just use the broken belt to rotate each of them the same direction / distance (maybe you can do this by cutting and clamping the belt to go around a smaller subset of the pulleys / tensioners / etc.). FYI - here's what the indexing marks look like on the front cam pulley:
 

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Yes, habbyguy is right as the numbers only show on the front cam. There should be a line engraved on the back cam that shows where no. 1 is. That should let you clock the rear cam to no. 1 when you bring it in-line with the mark on the back head that is like the one on the front. It's shown as B on the diagram habbyguy uploaded.

So if you decide to check TDC alignment, best practice should be to align everything to cylinder number 1. So back cam line on the mark, front cam no. 1 on the mark, crank at TDC.
 
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