Honda J35 Jumps Time, but no obvious causes?

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2009 Pilot 3.5, 215K miles.

Vehicle has misfires on cylinders 1-3. Found the rear camshaft to be 5 teeth off, front camshaft and crank are in-time. Timing Belt has an abnormal wear pattern, see attached.

The Hydraulic Tensioner shows no leakage and requires a normal amount of effort to compress using a vice. Water Pump and idler both spin smoothly w/o play. The tensioner adjuster bearing has a very slight amount of play, but some of these do. Rear Cam spins fine.

Prior service history:
- Aisin Timing Belt Kit was installed 2 years and 30K ago.
- Front camshaft was replaced 30K ago due to pitting and scoring. At the time, the front cylinder head had a significant amount of sludge but the rear cylinder head was clean. As part of this repair, the front cylinder head was removed and hot-tanked at a machine shop.

Any ideas?
 

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I had a weird problem in 2014 after replacing a bunch of seals and gaskets on our '97 Mazda MPV (3.0 SOHC V6).

I had pulled the cam gears to replace the front camshaft seals, and had not properly tightened the bolt on one.

The gear had walked partway off the front of the camshaft, shearing the woodruff key that was supposed to hold the gear in position, which then allowed the gear to rotate on the camshaft. The engine (non-interference, fortunately) ran terribly with one camshaft badly out of time.

I had to remove the rocker arms etc. to be able to pull the camshaft far enough forward to dig out the remnants of the key and install a replacement.

It was scary for this amateur, but all went well and the engine ran well when I put it back together.

It's unlikely this is your exact problem, but it's worth confirming the cam gears are oriented correctly on the camshafts.
 
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I know certain Audis have a timing gimbal so to speak that locks camshafts into place. Is there something similar required for Honda engines.
 
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I would be tempted to pull that rear cam out and check the cam bores in the head/journals on the cam.

Did either cam gear loosen up?
 
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No, both are tight.

Also, the rear cam pulley has never been touched.

Ok, just wanted clarification. The first half of my previous post still applies.

What did the cam bores in the front head look like?

How is the cam thrust for both cams?

Edit: did you shim the idler gear when you did the T/belt?
 

The Critic

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What did the cam bores in the front head look like?
Not great.

C7E9736C-8A95-44C2-ADA9-6CF7D0FAA787.jpeg

82FAF480-6D47-43E9-BF04-850B2AC86DC2.jpeg

I think the machine shop had “touched up” these areas when he worked on the front head, whatever that means.

No, the shim was not used. I have never had to install one and this one has never displayed any of the symptoms in that bulletin.
 
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Could you catch your nail on those? What was the cam journal to cam bore clearance?

If you could have caught your nail on those I would have probably replaced that head.

I still say to pull that rear cam and inspect the cam bores. I’d also be curious to see if that front bank head got worse . With no obvious issues with the result of the belt drive the issue is very likely with the cam(s). I’d probably go after that rear head first since that was the one that jumped.

You never said anything about cam thrust and if it is in tolerance?
 
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The Critic

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You never said anything about cam thrust and if it is in tolerance?
Honest answer: I didn’t check. When the front head was at the machine shop, they assembled the head with the cam. When I got it back, I set the valve clearance and shipped it.
 
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Honest answer: I didn’t check. When the front head was at the machine shop, they assembled the head with the cam. When I got it back, I set the valve clearance and shipped it.
Gotcha.

I meant to ask, when did this issue happen? Going down the road or on start up?

My last thought I had last night was that if it happened on start up, the tensioner could have had some internal bleed down overnight and then jumped on start up. Though one would think you’d have reduced tension on the belt on tear down. It would be very unusual for this to happen with no external leakage. And these engines will still usually run with reduced tension on the belt from leaking tensioners for a long time. I’ve seen exactly one time before on an older Mitsubishi engine with a hydraulic tensioner that it would slowly bleed down over night and cause a noise on cold start but would eventually go away. The tensioner somehow would recover after the engine was running .
 
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If you haven’t already pulled it all apart, but the belt back on and let it sit and see if the belt looses tension after sitting a while. If it doesn’t, I’d go with my first suggestion
 

dishdude

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Gotcha.

I meant to ask, when did this issue happen? Going down the road or on start up?

My last thought I had last night was that if it happened on start up, the tensioner could have had some internal bleed down overnight and then jumped on start up. Though one would think you’d have reduced tension on the belt on tear down. It would be very unusual for this to happen with no external leakage. And these engines will still usually run with reduced tension on the belt from leaking tensioners for a long time. I’ve seen exactly one time before on an older Mitsubishi engine with a hydraulic tensioner that it would slowly bleed down over night and cause a noise on cold start but would eventually go away. The tensioner somehow would recover after the engine was running .

The abnormal wear on the back of the belt supports the internal bleed down overnight theory.
 
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It almost looks like the bearing on the idler pulley was freezing up...something is up with that idler.

If that was the cause it would be quite obvious. The bearing would be extremely gritty.

If that is a KOYO bearing/pulley they are bulletproof. I have never taken one apart and found one bad. And never seen one fail.

Curious to see what he finds with hydraulic tensioner.
 

The Critic

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Gotcha.

I meant to ask, when did this issue happen? Going down the road or on start up?
Going down the road. The driver had just started driving and the CEL came on, followed by the misfire and low power.

If you haven’t already pulled it all apart, but the belt back on and let it sit and see if the belt looses tension after sitting a while. If it doesn’t, I’d go with my first suggestion
It had been sitting for a while (yesterday) when I looked at the engine. The belt was still tight.

If that was the cause it would be quite obvious. The bearing would be extremely gritty.

If that is a KOYO bearing/pulley they are bulletproof. I have never taken one apart and found one bad. And never seen one fail.

Curious to see what he finds with hydraulic tensioner.
Bearing spun smooth, but did have a small amount of wobble.

Anyway, we installed a new belt, hyd tensioner and tensioner adjuster. Miraculously the engine idles fine with no active misfires. Will probably do more diagnosis in the coming days.
 
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