Cylinder 4 misfire still acting up after spark plug replacement

[JoshKY]

My 4Runner is a 99' 4WD V6 standard trans 5spd 213k on it

Recently I noticed occasions when starting the truck up its idle was kinda burpy and had a noticeable shake to it and this would feel worse when letting out the clutch into low gears. This would come a go for about a week then started more frequently. Eventually the check engine light came on and would even blink at high speeds or when accelerating into 3000+ rpms. The code was for a misfire in cylinder four,

I changed all my spark plugs for new NKB's (while I was at it I also replaced the PCV valve and cleaned the throttle body just from the air intake side) hoping that this was the problem. After replacing the plugs it drove smooth for a day or so before the burp, shaky idle, and check engine light all came back. Cylinder 4 misfire was the code again. Today I swapped the coils for cylinders 2 & 4 to see if it was a faulty coil or plug wire. The vibration was even worse, but the check engine light did not come on. After about 10 minutes of driving with the coils swapped I heard what sounded like popcorn in the microwave from under the hood so I immediately pulled over and put the coils back in their respective cylinders. Now its driving smooth again and the check engine light is off, but I anticipate it will all be back within a day or so.

Where to go from here... any suggestions? Thoughts? Advice? Anecdotes?

 

[JayRolla]

My 4Runner is a 99' 4WD V6 standard trans 5spd 213k on it

Recently I noticed occasions when starting the truck up its idle was kinda burpy and had a noticeable shake to it and this would feel worse when letting out the clutch into low gears. This would come a go for about a week then started more frequently. Eventually the check engine light came on and would even blink at high speeds or when accelerating into 3000+ rpms. The code was for a misfire in cylinder four,

I changed all my spark plugs for new NKB's (while I was at it I also replaced the PCV valve and cleaned the throttle body just from the air intake side) hoping that this was the problem. After replacing the plugs it drove smooth for a day or so before the burp, shaky idle, and check engine light all came back. Cylinder 4 misfire was the code again. Today I swapped the coils for cylinders 2 & 4 to see if it was a faulty coil or plug wire. The vibration was even worse, but the check engine light did not come on. After about 10 minutes of driving with the coils swapped I heard what sounded like popcorn in the microwave from under the hood so I immediately pulled over and put the coils back in their respective cylinders. Now its driving smooth again and the check engine light is off, but I anticipate it will all be back within a day or so.

Where to go from here... any suggestions? Thoughts? Advice? Anecdotes?

Popcorn sound is arcing. You need to replace all wires and plugs. If a wire is bad than moving will do nothing as its still arcing. Pop hood at night with no lights anywhere and rev her. You may see the arc.

 

[JoshKY]

Popcorn sound is arcing. You need to replace all wires and plugs. If a wire is bad than moving will do nothing as its still arcing. Pop hood at night with no lights anywhere and rev her. You may see the arc.

The noise was only when the coils for cylinder 2 and 4 were swapped. Once I returned them to their respective plug holes it hasn't happened since, nor did it before I swapped them to test if it was cylinder 4's coil.

I just replaced all the spark plugs. Did you mean replace all wires and coils? Why is this necessary?

 

[JayRolla]

Your having misfiring issues. Its logical to replace the wires. I was not saying to replace the coils.

 

[Huey1202]

Hello, if none of the less-invasive repairs you've tried so far (replacing spark plugs, ign coils, etc.) fixes the misfiring issue then it could be a bad fuel injector or worst case, the engine is losing compression on the cylinder that is misfiring. The likely causes of compression loss is a cracked intake or exhaust valve or blown head gasket. In which case, you will have to pull the cylinder head to confirm. I would perform a leak down test on your cylinder and check if there are any leaks. I had the same issue as you on my '02 4Runner. It was idling rough and consistently throwing a cylinder no. 2 misfire code and I went through and replaced the spark plugs, ign coils, and fuel injector but it did not fix the problem. So I ran a leak down test on the problem cylinder and sure enough, air was leaking out of the tailpipe. I knew right then and there that the exhaust valve was leaking. Long story short, I ended up replacing the cylinder head with a re-built head and my 4Runner runs great now.

 

[JoshKY]

Hello, if none of the less-invasive repairs you've tried so far (replacing spark plugs, ign coils, etc.) fixes the misfiring issue then it could be a bad fuel injector or worst case, the engine is losing compression on the cylinder that is misfiring. The likely causes of compression loss is a cracked intake or exhaust valve or blown head gasket. In which case, you will have to pull the cylinder head to confirm. I would perform a leak down test on your cylinder and check if there are any leaks. I had the same issue as you on my '02 4Runner. It was idling rough and consistently throwing a cylinder no. 2 misfire code and I went through and replaced the spark plugs, ign coils, and fuel injector but it did not fix the problem. So I ran a leak down test on the problem cylinder and sure enough, air was leaking out of the tailpipe. I knew right then and there that the exhaust valve was leaking. Long story short, I ended up replacing the cylinder head with a re-built head and my 4Runner runs great now.

Thanks I've been doing some reading through old forum posts about misfires. The CEL light came on but the engine sounded and felt fine and the CEL light has gone off again. Looks like I'll test fuel injector by listening with a stethoscope and if there's any doubt to what I'm hearing, remove the intake manifold and test it with a multimeter. If that's not the problem I'll replace wire, then coil, then move on to worrying about a compromised cylinder.

One person in some thread I couldn't find a second time was going on about all the things I need to check and replace now that the truck has been driven at times when the CEL was blinking. They said the cylinder could have been flooded and to check the cylinder ring or gasket for oil and replace it. Maybe they mentioned to check the head gasket as well, wish I hadn't read it so late in the day. For now its running fine, but I won't feel alright with it until I pinpoint the issue and assess any damage.

 

[J_Schulz]

Hey y'all, first time posting on the site so hopefully I'm doing this right. I've been having a similar problem with my '01 SR5. Engine spat out a C4 misfire code about a month ago, after I got the CEL and the telltale stutter on acceleration. Took it to a local shop (I don't trust the techs at the local dealership to shoot me straight) and had the corresponding coil replaced. Car ran fine again for about 5 weeks, give or take, and now I'm getting a more severe and more frequent lag, but without any check engine light (except for a brief period of CEL flashing during a particularly bad misfire under heavy acceleration that cut back out 20 seconds later). I'm at a loss for what to do. Truck has just over 180k miles, it's well maintained, and I don't drive it hard. I've read through the relevant threads, save one that wouldn't load, and it seems like I have a couple of options:

1) Can of Seafoam: The cheapest fix. I haven't run a fuel treatment through the system since having the coil replaced, so this could help, but the problem seemed to develop too suddenly for simple engine buildup to be the culprit.
2) New plugs: I replaced the original plugs about 8y/70k miles ago, so maybe I have a fouled plug?
3) Other coils/wires/components: The further down the rabbit hole I go, the more complex and expensive it seems to get. Fuel injectors, seals, leaks, etc., most of which I lack the equipment and knowledge to check myself. Lots of options here, and I'd probably have to trust the guys at the shop to run it down for me.

The biggest thing I'm trying to figure is whether I'm able to fix this problem myself, or if it's going to take more tools/time than I have. I'm relatively good under the hood, but I'm a 1st year medical student with no time, less money and a limited arsenal of tools at my disposal. Hopefully the wisdom of the crowd can help me figure out what's up, faster than I could on my own.

Thanks y'all!

 

[thegipper]

Unfortunately it could still be a lot of things like:

Loss of compression in the cylinder
Bad injector
Spark plugs
Bad coil (replacement coil could also be bad in theory)
Plug wires
MAF
(fill in the blank)

I would scan for codes again and see if its #4 throwing that flashing misfire code. If it is, I would pull the plug and see how it looks. If it looks fine, I would check compression next. If both the spark plug and compression test are fine, you could try swapping injectors next and see if the problem follows the injector.

You could also try cleaning your MAF.

Again, there are just so many things that can cause a misfire so you'll just have to keep testing things. If you can't work on it yourself, I would try a different shop.

 

[feta]

easy injector test

An easy test for the injector is to put a long screw driver against it and then stick your ear on the other end. You should hear rapid ticking, then compare it to a known working one. See if they sound the same.

If suspect one is quiet, then it is not functioning.

If its clogged, it will still make noise and you need to swap injectors to see if misfire follows it to another cylinder.

I just went through this in December with my Sequoia

 

[Kanoe]

2) New plugs: I replaced the original plugs about 8y/70k miles ago, so maybe I have a fouled plug?

8 years on a set of spark plugs? Sheesh. No wonder the old girl is giving you grief. Start giving her some love! Cheap and easy thing you can do as part of your maintenance routine. Why have you waited?

And how old are those wires? If you don't know, then they are due for replacement too. Start with the cheap and easy things that you should be doing anyway before you start to stress about more complex causes.

 

[Ausumm]

8 years on a set of spark plugs? Sheesh. No wonder the old girl is giving you grief. Start giving her some love! Cheap and easy thing you can do as part of your maintenance routine. Why have you waited?

And how old are those wires? If you don't know, then they are due for replacement too. Start with the cheap and easy things that you should be doing anyway before you start to stress about more complex causes.

I got the "CYLINDER 5 MISFIRE" code, and started reading threads about it.
Seemed as if everyone had a pretty expensive solution.
So I dropped the 4R off at my mechanic,
and after some poking around...
discovered that the spark plug in #5 was falling apart! (his words)
On top of that...the other 5 plugs were either WAY too tight...
or so loose he could remove them with just his fingers!

Total cost was $200, and that was mostly for the labor.

I've only had the girl since December of 2015...and never changed the plugs.
I can only assume the owner before me hadn't replaced them in a long time.

So, a cheap fix AND it runs a lot better.
Can't wait to see if the gas mileage improves.

 

[T4R2014]

Sounds like the work of a good ol' DIYer.