2007 Honda Pilot 3.5 multiple misfires

[Number_35]

This is a friend's vehicle - a 2007 Honda Pilot 3.5 V6 with 305,000 km (189,000 miles) on it.

Earlier today it started running poorly, with the CEL flashing.

Codes are P0300 (general misfire) plus specific cylinder misfire codes (P0301 - 306), plus cat codes P0420 and P0430.

It had run well earlier, then suddenly started misfiring on all cylinders.

We discovered that the air-intake hose was badly cracked where it joins to the throttle body. Normally this would be a smoking gun, but there didn't appear to be a MAF after the air-filter box and before the hose.

Replacing the hose didn't help (although it did need to be done so the engine would not be running on unfiltered air).

I found a good vehicle-specific forum called Piloteers, which had a number of detailed threads about misfires on the 3.5. Unfortunately, this seems to be so common that sorting through the various possible causes is like trying to drink out of a firehose.

I don't imagine all six coils (COP) or spark plugs or fuel injectors would go bad at once, so I suspect something common to all six cylinders.

There were several comments about failing batteries, blocked PCV valves, and carbon buildup in the upper IM all causing misfires.

What's people's experience with the Honda 3.5 and misfires?

Thank you as always!

 

[michaelluscher]

Does this one have BCM?
Maybe burned a valve?
Timing belt skipped a tooth?
Fuel pump getting weak?

There's no smoking gun here, so it's probably best to start from the beginning, basics first

 

[dnewton3]

I believe another cause is the potential for stuck rings due to the cylinder deactivation management.
I've always wondered if several OCI treatments of a high-quality cleaning oil (such as HPL, VRP, Amsoil) would liberate the rings and resolve the issue.

 

[Number_35]

I believe another cause is the potential for stuck rings due to the cylinder deactivation management.
I've always wondered if several OCI treatments of a high-quality cleaning oil (such as HPL, VRP, Amsoil) would liberate the rings and resolve the issue.

Darn, I didn't realize these had variable displacement/cylinder deactivation that long ago. I've heard that can lead to a lot of problems.

A bit more information, probably not relevant to the present problems - the head gaskets were replaced several years ago, at c. 220,000 km (137,000 miles). The engine had been good since, until yesterday.

 

[Devo242]

Friend has an Odyssey of I believe the same year as your Pilot started experiencing a misfire issue. We tracked it to a failing timing belt tensioner allowing the belt to go slack and misfire, it sounded awful like a bad bearing in the motor. We put a new Aisin timing belt kit on it and it's been flawless for the past 30k or so.

With that said there could be a number of culprits as the Pilot board you're on mentions. You're just going to have to go through a diagnosis process and ideally start simple: how old is the battery and does it test as good? Could it be bad fuel that got into it? Etc, etc.

Also, the friend in question purchased a VCM muzzle for the van shortly after the timing belt kit went on, wishes he had done so sooner.

 

[Number_35]

Does this one have BCM?
Maybe burned a valve?
Timing belt skipped a tooth?
Fuel pump getting weak?

There's no smoking gun here, so it's probably best to start from the beginning, basics first

All good thoughts. The vehicle is outside, in cold temperatures (I think yesterday's high was -20°C (-4°F) and I was limited in time, so we didn't get much troubleshooting done.

I don't know when the TB was last changed, but presume it was done when the head gaskets were changed c. 85,000 km (52,000 miles) ago.

 

[Number_35]

Friend has an Odyssey of I believe the same year as your Pilot started experiencing a misfire issue. We tracked it to a failing timing belt tensioner allowing the belt to go slack and misfire, it sounded awful like a bad bearing in the motor. We put a new Aisin timing belt kit on it and it's been flawless for the past 30k or so.

With that said there could be a number of culprits as the Pilot board you're on mentions. You're just going to have to go through a diagnosis process and ideally start simple: how old is the battery and does it test as good? Could it be bad fuel that got into it? Etc, etc.

Also, the friend in question purchased a VCM muzzle for the van shortly after the timing belt kit went on, wishes he had done so sooner.

Good point about the tensioner - they don't always get changed with the TB.

I presume this engine uses a hydraulic tensioner.

 

[Barkleymut]

I dont think this vehicle has active cylinder management.
Have you checked the condition of the battery?

 

[rijndael]

I presume this engine uses a hydraulic tensioner.

Yes

And, I'm have another vote for checking the timing.

 

[Barkleymut]

I stand corrected

 

[Number_35]

Can I check timing on a COP system with a timing light? There are no conventional plug wires, of course, and I think the small wires from the ECU to each coil are simply supplying a constant -12 V and intermittent ground.

I guess the brute-force method is to pull the timing cover and see if the marks line up.

 

[Number_35]

View attachment 257268I stand corrected

That's good news!

(Edit: This vehicle is AWD, so no VCM. Phew!)

 

[rijndael]

Here's the timing mark alignment:

 

[Number_35]

Here's the timing mark alignment:

View attachment 257270

The engine is SOHC? I assumed DOHC.

That makes things easier!

Is it an interference engine?

 

[rijndael]

Is it an interference engine?

Yes

 

[LazyDog]

You can also try doing a Cam and Crank relearned procedure similar to GM's.

Another thing that you can check is the valve clearance, has they ever been done?

 

[Trav]

Check a plugged cat also, a simple back pressure test through the front O2 sensor hole is an easy and quick job.

 

[Number_35]

You can also try doing a Cam and Crank relearned procedure similar to GM's.

Another thing that you can check is the valve clearance, has they ever been done?

Presumably after the head gaskets were replaced, but I don't really know.

 

[Number_35]

Check a plugged cat also, a simple back pressure test through the front O2 sensor hole is an easy and quick job.

Besides the misfire codes, there were cat codes (P0420 and P0430). I don't know if the cat codes were there before, or coincide with the current issues. I'll ask the owner.

 

[rijndael]

It might be worth disabling the injectors and cranking it. Listen for the miss. If it doesn't sound smooth, check the timing.