FBO Engine Misfire

Redfire_Jimi

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Hi everyone, I am a newly registered member but not new to frequenting this site.

  • I have a 2005 4.6L motor with 146K on the dash. The car was been well maintained and serviced.
  • Last year I took on a 9 month project. I installed stage 2 heads from modularheadshop.
  • After putting ~1500 miles on the car, on June 01, ~90° day, I drove up a hill and really got into it. At the top of the hill, I put the car in neutral and coasted downhill, then I put the car into 3rd, and the car started misfiring. I was 15mins from home, so I pulled over, popped the hood, and let the car cool down. I started it ~5 times and it misfires. I drove home extremely slow because I didn't want to cause anymore damage to the car
  • I used my sct x4 to scan for codes and p0351 code came up. I spent 2 weeks diagnosing the coil on plug connectors and fuel injector connectors, I finally pulled the spark plug from cylinder #1 and the tip was bent. I also used a lightscope to see inside the chamber (see pics)
  • I think I may have timed the motor incorrectly.
  • I need help assessing the damage

IMG_5259.jpg IMG_5261.PNG IMG_5262.PNG


IMG_5260.PNG
 

Juice

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There is another thread on here recently posted with almost identical description.
Cant really see much in the borescope shots.
You will be at minimum pulling off one head to see the extent of the damage.
If the bore didnt get hurt, you are looking at ONE piston and one head repair.
Sorry to hear this.
 

Redfire_Jimi

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Thanks @Juice

I spent quite a bit of time on the timing, and I just dont understand how the timing could've been screwed up. I drove the car without any issues for 1500+ miles, and then all of sudden the car starts misfiring.

I will be pulling the valve covers later this week and post my findings
 

Juice

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You will likely find a broken intake valve.
 

Dino Dino Bambino

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Unfortunately it looks like the no.1 piston has contacted a valve as well as the spark plug electrode, and that valve is now probably bent. If it was broken altogether the damage would have been much worse.
You said you spent quite a bit of time checking the cam timing, and I don't think the engine would have run perfectly for 1500 miles if the cam timing was off, so I wonder if there's a weak or broken valve spring.
 

Juice

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Unfortunately it looks like the no.1 piston has contacted a valve as well as the spark plug electrode, and that valve is now probably bent. If it was broken altogether the damage would have been much worse.
You said you spent quite a bit of time checking the cam timing, and I don't think the engine would have run perfectly for 1500 miles if the cam timing was off, so I wonder if there's a weak or broken valve spring.
As pointed out in the other thread, the piston cannot hit the sparkplug. It was the head of the broken off intake valve that likely hit the sparkplug.
 

Dino Dino Bambino

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As pointed out in the other thread, the piston cannot hit the sparkplug. It was the head of the broken off intake valve that likely hit the sparkplug.

Good point. Then the damage is worse than what appears on the borescope photos. Let's hope the cylinder wall isn't also damaged and that there isn't a hole in the piston, otherwise there'll be debris scattered in the bottom end of the engine. At a minimum the right side head plus the no.1 piston will be trashed and that's bad enough.

Addendum:

you said you installed stage 2 heads from mod shop,,,, if so do you think they will honor the defective head they sent you?

I seriously doubt that but at this point, we still don't know how the damage happened. Earlier I suggested a weak or broken valve spring but another possibility is a severely worn valve guide that caused the valve to wobble around. In such a case, the Modular Head Shop WOULD be liable.
I'd suggest that you check the stem to guide clearance on ALL the valves as well as the condition of the valve springs when you remove and strip down the heads.
It looks like the outside portion of an intake valve is embedded in the piston.
 
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GlassTop09

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Thanks @Juice

I spent quite a bit of time on the timing, and I just dont understand how the timing could've been screwed up. I drove the car without any issues for 1500+ miles, and then all of sudden the car starts misfiring.

I will be pulling the valve covers later this week and post my findings
Hi Redfire Jimi,

I would also recommend to pull the intake manifold off & inspect the intake ports on #1 cyl to see both #1 intake valve heads.......from your pictures it looks like you did incur an intake valve strike on the piston.

Hope this helps.
 

whitmanink

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if i was a betting man,, id bet your valve is bent if not partly broken off,, ask me how i know.....

take the intake off ,,, you might find what your looking for in there ,,, best case,,, is a bent valve ,, worst case is you find bits in the intake or through the pistion
 

whitmanink

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you said you installed stage 2 heads from mod shop,,,, if so do you think they will honor the defective head they sent you?
 

Midlife Crises

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Looking closely at the divot beat into the piston it’s clear the valve smacked the piston. I think I can see the compression ring which means chunks of piston bouncing around the cylinder likely bent the spark plug. Just guessing the valve head has not completely broken off but is bent.
Check the condition of the valve springs when you tare it down.
 

Juice

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I am a betting man.
One of the intake valves IS broken off.
That is not likely from a defect.
 

Redfire_Jimi

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if i was a betting man,, id bet your valve is bent if not partly broken off,, ask me how i know.....

take the intake off ,,, you might find what your looking for in there ,,, best case,,, is a bent valve ,, worst case is you find bits in the intake or through the pistion

I will be taking the valve covers and the intake manifold off this weekend.

The weird thing is the car drove normal for almost six months now. It hasn't been to the drag strip, but occasionally I drive the car like it should be driven. Also, it runs on idle without any weird noises, as soon I put it into gear is when it starts getting clunky.
 

Redfire_Jimi

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Hi Redfire Jimi,

I would also recommend to pull the intake manifold off & inspect the intake ports on #1 cyl to see both #1 intake valve heads.......from your pictures it looks like you did incur an intake valve strike on the piston.

Hope this helps.

Thanks.
What would cause an intake valve strike on the piston? I am asking this question because ModularHeadShop did all the work on the heads. All I had to do was install them and line up the timing marks on the chain.
 

Redfire_Jimi

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Good point. Then the damage is worse than what appears on the borescope photos. Let's hope the cylinder wall isn't also damaged and that there isn't a hole in the piston, otherwise there'll be debris scattered in the bottom end of the engine. At a minimum the right side head plus the no.1 piston will be trashed and that's bad enough.

Addendum:



I seriously doubt that but at this point, we still don't know how the damage happened. Earlier I suggested a weak or broken valve spring but another possibility is a severely worn valve guide that caused the valve to wobble around. In such a case, the Modular Head Shop WOULD be liable.
I'd suggest that you check the stem to guide clearance on ALL the valves as well as the condition of the valve springs when you remove and strip down the heads.
It looks like the outside portion of an intake valve is embedded in the piston.

Hey Dino, I changed the oil after all this happened. And the old oil did not have any metal debris. Though, I found 2 pin bearings (see image). I also took measurements.IMG_5250.jpg IMG_5246.jpg
 

Juice

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Thanks.
What would cause an intake valve strike on the piston? I am asking this question because ModularHeadShop did all the work on the heads. All I had to do was install them and line up the timing marks on the chain.
My best guess on PTV contact is either cam timing was off or the cams installed needed phaser limiters and/or tune adjustment.
This is all speculation till you pull the heads.

From personal experience, my first street bike broke an intake valve after months of running. Cam chain was off a tooth.

Yes, the head could be fixed if its just a valve issue. Unfortunately, the chamber is probably hammered from debris bouncing around in there.
 

Dino Dino Bambino

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Hey Dino, I changed the oil after all this happened. And the old oil did not have any metal debris. Though, I found 2 pin bearings (see image). I also took measurements.View attachment 83295 View attachment 83296

It's possible that when the piston hit the valve, the corresponding cam follower was broken and the needle bearings fell out. I suspect you'll spot it the minute you pull the passenger side valve cover.
 

Midlife Crises

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What would cause an intake valve strike on the piston?
You put it in third gear after you crested the hill. Did you over rev and float the valves? I have scattered a couple small blocks doing similar things.
I agree those needle bearings are from a cam follower.
 

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