Really, really weird misfire problem

I

importman

New member
Hey guys, Just hoping someone has experienced this problem before on a 4th gen V6 and can give me a silver bullet. I've been an ASE Master Tech for over thirty years and it makes no sense to me. Also questioned my ex brother in law who's been a Toyota master tech since 1984 and he hadn't seen it and had no real advice. While driving on the interstate yesterday my T4R started misfiring. So my first thought was, no big deal, probably time to replace a coil. Luckily I had a scan tool with me and I checked and it is actually misfiring on #1 and #2 at the exact same time. Misfire counts show the same on both cylinders as they happen. Highly unusual. They started acting up at the same time and they misfire at the same time. It only does it under load or at idle in gear. If I run it with the rpms up a little bit on the road it won't do it. I've verified it's not the coils or the plugs. I'm 90 % sure it's not injectors although I haven't checked them yet. It feels exactly like every ignition misfire I've ever felt. You squeeze the throttle on the road and when the load gets up it begins to misfire. Or, I can put it in gear and hold the brake and build it up and it does it. Like I said, I'm a master tech and I'm at a loss. If I don't come up with something by Monday I'm gonna make a call to Identifix and see if they can help. So, has anyone ever dealt with this? It's an 05 4.0 so it's not gonna be like the 3rd gens with waste spark where one coil can disable two cylinders. Thanks in advance for any help.
Oh, I want to add that I did search the forum and could not find where anyone else had posted about this before I posted.
 
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I am no guru, no pro mechanic, and do not have this misfire.

But I would like to ask, since the firing order is 123456 could the multiple misfire be caused by the engine not recovering from the original misfire in time for the next cylinder to fire on schedule ? Toyota's use crankshaft speed for detection right ?

Would it not be prudent just to go ahead with the the plug, coil, vacuum, fuel pressure testing ? Would under load be more vacuum leak probable ?

Not trying to be a pain, just asking.
 
Seasparrow said:
I am no guru, no pro mechanic, and do not have this misfire.

But I would like to ask, since the firing order is 123456 could the multiple misfire be caused by the engine not recovering from the original misfire in time for the next cylinder to fire on schedule ? Toyota's use crankshaft speed for detection right ?

Would it not be prudent just to go ahead with the the plug, coil, vacuum, fuel pressure testing ? Would under load be more vacuum leak probable ?

Not trying to be a pain, just asking.
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Hello, Thank you for your response. Yes it does use a crankshaft position sensor to determine spark. It basically lets the ECU know the where the crankshaft is in its rotation so it knows when to send spark to each cylinder. I've thought a lot about it since this happened and the only way I can see it affecting just those two cylinders is if there is some damage to the reluctor wheel that the sensor reads. Since 1 and 2 fire back to back it is feasable that a couple of teeth missing or damaged on the wheel could cause this. That's one thing I'm going to look at when I get back on this thing. As far as checking the coils and spark plugs; I moved coils around yesterday while stopped at an Advance Auto parts store. No changes when the coils were moved. I also went ahead and installed new plugs on the passenger side while I was at it. I didn't do the driver's side since it's more difficult and I was having to work with an awful socket set I bought at the Advance store for $19.99. The spark plug socket wouldn't even hold on to the plugs to pull them out. I had to buy a magnet to pull them up out of the holes. Plus, after changing those three and moving the coils around I was satisfied that they are not the problem. I'll stick the other three plugs in when I get back to it. As far as fuel injectors and fuel pressure; I can't see the fuel pressure affecting only two cylinders and the others performing perfectly. The one thing I plan to check on the injectors is this: I worked on a vehicle one time that had rust/trash in the fuel system and it made it to the injector rail and clogged up the two injectors that were at the far end of the rail from where the fuel comes in at. Possibly, something broke loose and did that to mine since 1 and 2 are in that location. The problem I see with that is, I would expect them to misfire pretty much all the time instead of coming and going like they are. Anyway, thank you for taking the time to reply. I do appreciate it. You've given me some things to think about.
 
Not that I have a solution, but high rpms is when the vvti kicks in. No other codes? Did the heads ever have to come off for any reason?


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ruckerz said:
Not that I have a solution, but high rpms is when the vvti kicks in. No other codes? Did the heads ever have to come off for any reason?


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Click to expand...

Hey Ruckerz, Thanks for the reply. To my knowledge the heads have never been off and the timing chain is original. I've only had it a couple of months so I could be wrong, but I don't think so. It has no other codes. Not sure if the VVTI could affect two cylinders on opposite banks without affecting any others, though. Thanks again! I do appreciate you taking the time to reply.
 
Ahh yeah sequential cylinders misfiring don’t make sense

Perhaps it could be chain stretch? Either the timing chain or the cam chains.

You can look down at the timing chain tensioner with just the passenger or right hand side valve cover off to see if it’s really extended.


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ruckerz said:
Ahh yeah sequential cylinders misfiring don’t make sense

Perhaps it could be chain stretch? Either the timing chain or the cam chains.

You can look down at the timing chain tensioner with just the passenger or right hand side valve cover off to see if it’s really extended.


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Click to expand...

Man I really hope it's not a stretched chain. I haven't totally ruled that out but I can't really see how a stretched chain would only affect those 2 cylinders. Thanks again for your input.
 
techno said:
I assume with you being a master tech that you've already referred to the Toyota fsm for help, but just in case, here's a link where you can find the trouble shooting procedure for those codes.
Toyota Factory Service and Repair Manual - 2007 4Runner + Updates
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Hey Techno, Thanks for that. I do have alldata so I have the service manual but the way it's laid out in your link makes it a little easier to navigate. I've been scouring through the FSM this weekend with little to show for it so far. The diagnosis procedure in there is useful, but I'm not sure if it will lead me to the solution. This is just a really obscure problem. But I will find it eventually. Thanks again for your help. I do appreciate it.
 
I am not a mechanic but I had an idling problem that seemed like misfiring when I first got my used 05 a couple months ago. Obviously I was terrified that I had just bought something that was going to need major repair but turned out to simply need an idle reset because the battery had been replaced. I fixed it in 5 minutes :)
 
This is going to sound dumb, but how long have you had the gas in the tank? A couple years ago I had mine sitting for a few months while I was working on it off and on. When I got it back together and drove it, I would drive for about 10-15 minutes and then it would start misfiring on cylinder 1. If I kept driving it would start misfiring on other cylinders.

I started swapping hardware around to other cylinders, but the misfire would always start on cylinder 1. I finally decided to put more fuel in it and the problem disappeared. Just throwing it out there in case you got a bad batch of fuel or what you have in your tank is old.
 
Docholliday5645 said:
I am not a mechanic but I had an idling problem that seemed like misfiring when I first got my used 05 a couple months ago. Obviously I was terrified that I had just bought something that was going to need major repair but turned out to simply need an idle reset because the battery had been replaced. I fixed it in 5 minutes :)
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I really wish mine could be that simple. But, since it's doing it on the highway, and it's a dead misfire on those two cylinders, I won't be that lucky. Thank you for taking the time to reply. I appreciate it.
 
djpope09 said:
This is going to sound dumb, but how long have you had the gas in the tank? A couple years ago I had mine sitting for a few months while I was working on it off and on. When I got it back together and drove it, I would drive for about 10-15 minutes and then it would start misfiring on cylinder 1. If I kept driving it would start misfiring on other cylinders.

I started swapping hardware around to other cylinders, but the misfire would always start on cylinder 1. I finally decided to put more fuel in it and the problem disappeared. Just throwing it out there in case you got a bad batch of fuel or what you have in your tank is old.
Click to expand...

The gas that's in there is new. I've been through quite a few tanks since I got this a couple months ago. But, I might have gotten some bad gas. That's something I'll need to look at. Just curious that it's only affecting 2 cylinders. But it did that on yours so who knows? Thanks for the reply. I appreciate it!
 
importman said:
I really wish mine could be that simple. But, since it's doing it on the highway, and it's a dead misfire on those two cylinders, I won't be that lucky. Thank you for taking the time to reply. I appreciate it.
Click to expand...

Sorry for the bad luck, hope you resolve it soon and reasonably inexpensively!!
 
importman said:
Man I really hope it's not a stretched chain. I haven't totally ruled that out but I can't really see how a stretched chain would only affect those 2 cylinders. Thanks again for your input.
Click to expand...


If the links on the timing chain are stretched precisely at the cam position where those cylinders are involved in the timing.


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ruckerz said:
If the links on the timing chain are stretched precisely at the cam position where those cylinders are involved in the timing.


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Click to expand...

Hey Ruckerz, Yeah, it can't work like that. There are no specific links that line up for a particular cylinder. Yes, when you time it they have to be in time but after the engine is started the links don't line back up with the marks on the gears every revolution. In fact, going from memory when I was a Nissan tech, you line up the silver links on the chain with the marks on the gears, then it takes something like 90 some revolutions before the links line back up with the marks again. Thanks for your effort again.
 
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