Misfire in cylinder 4.

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HarryM

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My engine started running a little rough so I took it to my mechanic and he determined that I have a misfire in cylinder 4. So far he has verified that the injector, plug, coil, injector pulse, compression, and coil signal are all good. He says his next step is to put in a new VVT Solenoid. If that doesn't fix it he is talking timing chain (although i don't know how a bad timing chain can only affect one cylinder). Does it sound like he's on the right track? Anything I should be suggesting to him, or be asking about?

Thanks

Harry
 

1955moose

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Well first off Harry always post your year, engine, and 2or 4 wheel drive. Misfires can be a number of things. How did he determine all your ignition was fine, Eg spark plug, and so on. Without swapping coil to another cylinder, or replacing it, or spark plug, they still could be misfunctioning. We have another member that has same situation as you. I can't see how a variable valve timing solenoid would only affect one cylinder. Usual symptoms are check engine light on rough running, problems accelerating up grades. What codes did he come up with. Let us know your results. I think he's reaching, and doesn't know. A worn timing chain would not cause one cylinder misfire. How many miles? A worn timing chain/guides would cause a slapping sound coming from front timing cover, and a little loss of power, but again not a misfire. Hate to say it, but you might consider a shop with more experience working on these vehicles.

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HarryM

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Hi Moose,

You are correct, I should have posted about my truck. 2006 Eddie Bauer, 4wd, 5.4. It has about 135K miles. And since mine has been in the shop, I have been reading about the other member's issue.

This started a few days ago, just seemed that it would shake more than normal when cold and in gear at a stop light. It would smooth out after it warmed up.

He did pull the plug and the coil and switched them to another cylinder, with no change. Still cylinder 4. I would assume that a compression test would rule out a valve or a weak spring. The engine light never came on, but from the other member's posts, one may have shown up without turning on the CE light. He hasn't mentioned pulling codes. It seemed to start and accelerate same as normal. I haven't noticed any other new noises.

I did ask how a timing chain can cause a misfire in just one cylinder. I wasn't really given an answer, but that was from the guy up front, not the mechanic himself.

I've gone to this mechanic for many years and he has always been very good on his repairs.

So, anything else I should be asking him? Any other ideas what it may be?

Thanks

Harry
 

1955moose

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He had to retrieve codes to know it was #4. If he's 100 percent sure that all is fine with electrical including all connections up to coil and fuel injectors, its possible you've got a lean condition causing rough idle. That can be caused by exaust leak, intake leak, especially around intake manifold gasket. Very common failure on all 4.6/5.4 motors. The manifold cracks its plastic, and the gasket fails, causing both intake, and coolant leaks. Have him do a smoke test of motor to check for any intake leaks, something is going to show. Also not related directly but change little pcv rubber grommet. They fail, cause all kinds of issues.

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JExpedition07

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moose has good ideas. I will add this does not sound like anything to do with the timing chain... whatsoever.
 
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HarryM

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My mechanic traded out the VVT Solenoid and it didn't fix the problem. We talked and he admitted they were stumped, so we all agreed to move my truck to their sister shop that has better diagnostic equipment and more experienced mechanics. I also gave him the link to this forum and he said he would watch it in case anyone here had other suggestions. For all the work that he did, he isn't charging me anything because ultimately they weren't able to fix it. That's a stand up policy to me.

So any other ideas, let me know. And I'll post anything I hear.

Harry
 

Tdh777

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I have a very similar issue, rough mild shaking when stopped in gear, no misfire codes or pending. New plugs, coil packs, and injectors have been cleaned. All signals are good to the injectors and coils.
Don’t really see any other symptoms than the “rough” idle in gear. Not very prominent but it just doesn’t seem right. Hasn’t ever idled this way before. My next step is to have everything fogged and see where the leak is.
 

Canaris

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My 2001 Expy was doing the same, turned out one of the heater hoses was leaking at the firewall right over the #4 coil pack.
 
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Just spitballing, but have you tried resetting your throttle body set point, or cleaning the throttle? You'd usually get a code if there was a problem there, but it's pretty easy to remove, scrub with cleaner, then reset if needed. Just a thought, depends how much spare time you have. Never a bad idea to clean your throttle body anyway, if it's never been done and you have high miles. I had to do mine last fall, it's an '05 about 135k miles and totally died on me one day while driving, gave a "check throttle body" message.

Sounds like you've well ruled out the coil/plug, which is my go-to and almost always the culprit with these symptoms. Swapping with another cylinder and seeing if the code chased it is the easiest way to rule that out. If the shop didn't charge you for diagnostics, that's an honest business, sounds like someone you can trust.
 

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