Hey Captsolo, Well it's a V6 so it can't be the timing belt. It's possible the chain could've jumped a few teeth but at this point I don't think so. Crank position sensor is something I plan to look at. Even it seems somewhat unlikely though since it's only affecting 2 cylinders. But no, the misfire doesn't happen all the time. It only happens when it's under a load. It will do it at idle if it's in gear, and it does it when driving under even a small load. At a steady cruise with almost no load it doesn't do it at all. And it's both #1 and #2 cylinders. They both misfire at exactly the same time. And they both starting doing this at exactly the same time. It feels just like every ignition related misfire I've ever dealt with. That's what is making this so difficult. Thank you for your reply and for any ideas you may have.
Really, really weird misfire problem
- Thread starter importman
- Start date
Hey Captsolo, Well it's a V6 so it can't be the timing belt. It's possible the chain could've jumped a few teeth but at this point I don't think so. Crank position sensor is something I plan to look at. Even it seems somewhat unlikely though since it's only affecting 2 cylinders. But no, the misfire doesn't happen all the time. It only happens when it's under a load. It will do it at idle if it's in gear, and it does it when driving under even a small load. At a steady cruise with almost no load it doesn't do it at all. And it's both #1 and #2 cylinders. They both misfire at exactly the same time. And they both starting doing this at exactly the same time. It feels just like every ignition related misfire I've ever dealt with. That's what is making this so difficult. Thank you for your reply and for any ideas you may have.
I dunno. Depending on the build date and mileage you probably know the head gasket issues these cars have. It’s unclear whether or not it’s been done for your car but I’ve read of cases where the owner machined they head because it over heated and or screwed it up on the way out. Engine never runs smoothly again. And machining heads is a no no for these engines. Just a thought but sounds like you need more diagnosis like ripping off the valve covers and or timing chain cover to see what’s going on inside?
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You’re right but you’d be surprised it doesn’t take many revolutions to get back to the original section of the chain . Less than 20.
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Hey Ruckerz,, You're right, I don't know for sure about the head gaskets. I don't think they've been changed but I have no way of proving it. But, this car has run perfectly for 7-8k miles since I got it. Then all of a sudden it began misfiring. And it's always cyls 1 and 2 every time, and no other cylinder is affected. So, I don't think it could be head gasket or timing chain related. If a chain is stretched at any point it's going to retard the timing on the cam(s) it drives at all times. Of course the vvti can offset some of that but either way it will affect all cylinders equally. Again, I do appreciate your input and if you happen to think of something else, by all means let me know. I think my next step is going to be to call Identifix. They saved by butt a number of times when I had my shop and ran into something unique like this. Thank you again!
I think you're right about the chain, if it was stretched or skipped a tooth you would be getting a cam/crank position mismatch fault, not a misfire fault.
That's true. I do still wonder if maybe something has happened to a couple of the teeth on the reluctor wheel that the crank sensor reads off of. Unfortunately, it's still going to be a little while before I can check this stuff. I'm stuck in NC at our vacation camper and the 4runner is at home in SC. Thank you for your input!
Seasparrow
New member
How did the plugs look ?
I am placing my bet on the injector, 5 bucks worth.
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I am placing my bet on the injector, 5 bucks worth.
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It may turn out to be injectors. I'm still thinking something more unusual, like a wiring problem or bad computer. I'll be sure to post on here when I finally find out what the problem is.
I am glad I am not the only one having this issue with the 4.0 engine. I am working on a 2005 4Runner Sport V6 4 Wheel Drive. This has been ongoing for 8 months already. Change something and it is good for a couple of weeks. Then back to same issue. It first started out around 40 mph under load and now it is hesitating at other speeds. The engine light has not been coming on again since the throttle body was replaced about 2 months ago. The hesitation at times is not too bad and at others it's bad. If anyone has suggestions and/or if you come up with solution please let me know. Thanks in advance.
spdrcr29
New member
Aside from swapping the coils and injectors to another cylinder and seeing what happens, i'm going to go out on a limb here and say its possible that you have a head gasket problem and a small amount of coolant is getting into at least one or both of those cylinders. Do you notice the misfire at cold start up at all? After driving it for a while, you can pull one or both of those plugs and look for any steam coming out. You might have to hold a mirror over the plug hole when doing this. Something else you can do is drive it for a while and then park it overnight. Pull either #1 or #2 plug or both and use a borescope to see if you can see any traces of coolant on top of the pistons. Good luck finding the issue!
Thanks for your help. It's not the head gaskets though. I was on the interstate when it started and I stopped at an Advance Parts store and bought a tool set and moved the coils around to different locations and nothing changed, (the misfires stayed on 1 and 2). I also pulled the plugs and they were worn some but no sign of coolant or oil or anything. They looked perfectly normal, just worn from age. I went ahead and replaced the ones on the passenger side. I didn't do the driver's side since I was working with very poor tools and in the parts store parking lot. I continued home which was between 150-200 miles. It only misfires under load so I drove in 4th gear and kept the rpms up a little and was able to limit the misfires. Through all of that it never heated up, steamed, or showed any signs of head gasket failure. The coolant level didn't move at all either. Anyway, I haven't had a chance to work on it since then because I'm hunkered down in our mountain vacation place which is about 300 miles from home. Once I get home I'll start back on it and I'll probably call Identifix and see if they can help. Thank you again for taking the time to reply.
I'll be sure to let you know as soon as I get it straight.
spdrcr29
New member
No problem! When comes to hard to diagnose issues, i sometimes like to think outside the box when "everything else as already been checked" but still having issues. Not saying that my outside the box thinking is always correct, because i'll be the first to admit that I don't know it all. Sometimes just thinking differently about how to diagnose issues can end up helping to solve the problem. Well, hopefully you will figure it out soon and be sure to let everyone know what you found!
I will definitely let everyone know once I get it figured out. Thanks again for your help!
Thank you. It is greatly appreciated. I keep saying the car is possessed or something.
I'm impatient so I dug through importman's thread quotes and found that his issue was a bad spark plug, see post #4 here:
https://www.toyota-4runner.org/4th-...fire-codes-p0300-p0302-p0303.html#post3646333
https://www.toyota-4runner.org/4th-...fire-codes-p0300-p0302-p0303.html#post3646333
Much smarter people have had some good ideas on this thread so far. I hope I’m using the right terminology. Aren’t there 2 filters, a 14 mm bolt just by the #1 and #2 cylinders? I think it’s the vvti filters but I’m going to have to dig into my fsm to verify. Could those be affecting this somehow? To be honest I’m not sure what they do completely.
Just checked. It is the variable valve timing oil filter. Not too sure if it could be the issue but depending on the mileage and since it’s fairly new to you, maybe the po wasn’t the best at oil change intervals? Anyway looks easy enough to clean and reinstall. Im sure you have the info at hand, sorry for not providing the information here.
Just checked. It is the variable valve timing oil filter. Not too sure if it could be the issue but depending on the mileage and since it’s fairly new to you, maybe the po wasn’t the best at oil change intervals? Anyway looks easy enough to clean and reinstall. Im sure you have the info at hand, sorry for not providing the information here.
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Thank you for posting this. Until this minute I didn't realize I never posted the conclusion to this. My apologies to everyone. I always try to make sure I let everyone know what the problem was. (And I talk crap about people who don't). Again, I'm sorry I left everyone hanging. To see the answer, go to the link djpope09 so graciously posted above.
