2000 V6 - Intermittent misfire cylinder #5

[BabeGTR]

Aloha,

Looking for some guidance. Engine randomly started misfiring/sputtering badly. CEL came on, P0305 - Cylinder 5 misfire.

When car is started with cool engine, no issues at all. After shutdown and a restart when the engine is at temp, immediately sputters on idle, in park and while driving.

Inspected each coil, boots, wires and plugs on the right side, nothing out of the ordinary. Added some fuel injector cleaner, no joy.

Thoughts?

2000 Sr5 180k miles - Timing belt change 1 year ago, new plugs and wires 2 years ago.

 

[gamefreakgc]

Switch the coils around and see if the code changes. Doesn't cost anything and eliminates that piece. Next pull out the spark plug in cylinder 5 and inspect for damage. If it looks fine, also not the problem. After that I suspect the injector. If you are able to get to it unplug the injector and test the resistance across the two prong with an multimeter and read the ohms, or resistance. Should be within a set value that you can compare against.

 

[BabeGTR]

Coil on the bottom looks worn, from the bad cylinder 5. Coil on the top from cyl 3. Swapping now.

Update: Swapped 2 coils, reset the CEL, misfire returned, CEL displayed the same cylinder 5. While I was in there, I inspected #5 spark plug. It appeared slightly fouled. Will replace that plug, try again and follow gamefreakgc advice and ohm test the #5 fuel injector.

 

[Zhehan]

You can replace the coil boots. You should replace them when you replace the wires. Get NGK plug boots and wires.

 

[charmizzzard]

Is NGL the recommended brand for plugs and boots? I know we have 3 coils and 3 wires, right?

 

[BabeGTR]

Update:
Still misfiring once warm
-Replaced #5 plug with identical NGK
-Disconnected each of the 3 passenger side fuel injectors and ohm tested:
-2 good cylinders were 15.6
-#5 showed 18.6
-Cleaned MAF

Thoughts?

 

[heat]

Compression?

 

[mtbtim]

Update:
Still misfiring once warm
-Replaced #5 plug with identical NGK
-Disconnected each of the 3 passenger side fuel injectors and ohm tested:
-2 good cylinders were 15.6
-#5 showed 18.6
-Cleaned MAF

Thoughts?

Did you ohm the injectors while they were hot? The reason why I ask is there's usually different levels of resistance based off the temperature of the component. Since your problem only happens when warm, the injector might be out of spec and malfunctioning when hot. If the injectors weren't hot when you tested them, this might skew your result.

A compression problem would be constant. I believe your issue is most likely fuel related since you did swap coil packs and the misfire didn't follow the coil pack, eliminating the possibility that spark is the problem. Since I'm guessing you don't have a fancy scanner with a scope, I would suggest your next step is pulling the fuel rails and swapping the position of the #5 fuel injector with another one and then see if the misfire follows it.

 

[Toaster134]

I had the same issue with a rough idle after a warm start and it was a bad injector. Swap like Timmy says to know for sure.

 

[BabeGTR]

Did you ohm the injectors while they were hot? The reason why I ask is there's usually different levels of resistance based off the temperature of the component. Since your problem only happens when warm, the injector might be out of spec and malfunctioning when hot. If the injectors weren't hot when you tested them, this might skew your result.

A compression problem would be constant. I believe your issue is most likely fuel related since you did swap coil packs and the misfire didn't follow the coil pack, eliminating the possibility that spark is the problem. Since I'm guessing you don't have a fancy scanner with a scope, I would suggest your next step is pulling the fuel rails and swapping the position of the #5 fuel injector with another one and then see if the misfire follows it.

mtbtim: Correct, I do not have adequate equipment for testing. I tested the injectors while the vehicle was still warm, the plugs were still hot. (about 45 min after a drive). Leaning towards letting a tech do the proper testing with a focus on the injector.

Any thoughts on the CAM position sensor possibly being a culprit?

 

[mtbtim]

mtbtim: Correct, I do not have adequate equipment for testing. I tested the injectors while the vehicle was still warm, the plugs were still hot. (about 45 min after a drive). Leaning towards letting a tech do the proper testing with a focus on the injector.

Any thoughts on the CAM position sensor possibly being a culprit?

The thing is, are you going to get a tech that is good at diagnostics. The test I'm referring to requires a tech that knows how to analyze waveforms with a scope. There's LOTS of mechanics that either don't own the equipment necessary to perform this type of test, or they own one, but don't really know how to use it. This is the sort of PHD level of auto mechanics. I'm learning a little about it now, and it's a mind boggling amount of knowledge to absorb. I think you should try the injector swap, because this is a diagnostic you can do on your own. It won't cost you any money, but it will cost you some time.

https://www.youtube.com/watch?si=JgHpvTI4FWNCtZKM&v=N-lhZIWOkyU&feature=youtu.be

 

[Sparky 97Runner]

Are you loosing coolant or see air bubbles in the coolant overflow reservoir while the engine is running? Cylinder #5 is the most common for head gasket failure and you mentioned a fouled plug. Hopefully this is not the case but I'd consider doing a leak down test on #5 cylinder.

 

[mtbtim]

Are you loosing coolant or see air bubbles in the coolant overflow reservoir while the engine is running? Cylinder #5 is the most common for head gasket failure and you mentioned a fouled plug. Hopefully this is not the case but I'd consider doing a leak down test on #5 cylinder.

I've actually heard more issues with cylinder #3, usually from cracks in the head.

If he was having a head gasket or cracked head issue, these usually present themselves with a rough start that smoothes out once the engine warms up a little. This is because when you shut down the engine and you leave it sitting for a while, or over night, the cooling system is still under pressure and the pressure slowly forces coolant into the cylinder via an imperfection in the head gasket or a crack in the head that has grown into a coolant jacket. The coolant settles onto the top of the piston, and when you start it up, that coolant fouls out the spark plug for a while causing the misfire. You usually see a bunch of white smoke that clears up and then the engine runs fine until you do another cold start.

I usually tell people to do a compression test followed by a leak-down test for a misfire issue, but a misfire that only presents itself when warm leads me to believe this is not a compression problem, it's a fuel problem or spark problem.

 

[Sparky 97Runner]

I've actually heard more issues with cylinder #3, usually from cracks in the head.

If he was having a head gasket or cracked head issue, these usually present themselves with a rough start that smoothes out once the engine warms up a little. This is because when you shut down the engine and you leave it sitting for a while, or over night, the cooling system is still under pressure and the pressure slowly forces coolant into the cylinder via an imperfection in the head gasket or a crack in the head that has grown into a coolant jacket. The coolant settles onto the top of the piston, and when you start it up, that coolant fouls out the spark plug for a while causing the misfire. You usually see a bunch of white smoke that clears up and then the engine runs fine until you do another cold start.

I usually tell people to do a compression test followed by a leak-down test for a misfire issue, but a misfire that only presents itself when warm leads me to believe this is not a compression problem, it's a fuel problem or spark problem.

I think it's because #5 cylinder is so close to the heat from the exhaust where it crosses over and connects at the back of the engine. I've dealt with a number of #5 cylinder gasket failures especially on the 3.0 which was a nightmare engine for Toyota. Totally agree that OPs symptoms seem opposite but it wouldn't hurt to check at least check for bubbles and coolant level which is super easy. Totally agree with swapping injectors as well. It's just a little more of a pain.

 

[mtbtim]

I think it's because #5 cylinder is so close to the heat from the exhaust where it crosses over and connects at the back of the engine. I've dealt with a number of #5 cylinder gasket failures especially on the 3.0 which was a nightmare engine for Toyota. Totally agree that OPs symptoms seem opposite but it wouldn't hurt to check at least check for bubbles and coolant level which is super easy. Totally agree with swapping injectors as well. It's just a little more of a pain.

I think it's all a pain for the OP. Checking for bubbles is simple, but I kind of doubt he owns either a compression tester, leak down tester or owns an air compressor to use with the leak down tester.

Even though swapping the injectors is some decent labor, it really doesn't require any specialized tools.

 

[cthomsen99]

I had similar symptoms in a 99. New injectors solved the problem.

 

[gamefreakgc]

Update:
Still misfiring once warm
-Replaced #5 plug with identical NGK
-Disconnected each of the 3 passenger side fuel injectors and ohm tested:
-2 good cylinders were 15.6
-#5 showed 18.6
-Cleaned MAF

Thoughts?

I think you've done all the diagnosis you possibly can. It's not spark, so it's fuel. Time to replace the injector.

If you had bad compression, the problem would be there all the time and not intermittently. No need for a compression check.

 

[MaineRunna]

I doubt it is a head gasket, more likely to misfire cold and would be using coolant. Could do a leak down test or hydrocarbon test to confirm. Almost definitely not a mechanical issue like a valve spring. Not going to be the cam sensor either. You have for the most part ruled out an ignition problem so it almost has to be a bad fuel injector. Overall I don't replace a lot of fuel injectors on any model vehicles, but I have replaced quite a few injectors on the Toyota 3.4L. One thing to do is listen to the injectors with a stethoscope, they should have a nice solid metallic clicking noise when operating properly. You could possibly have a wiring or ECM problem, but highly unlikely.

 

[BabeGTR]

Thanks for all the replies. I discovered an exposed wire on the #5 coil connection. Looks like a past mechanic tapped into it and soldered a lead in wire. The electrical tape degraded to the point I could see it. I removed the tapped in wire, heat shrunk then taped it up some more, cleared the CEL, it ran well when cold, slight sputter returned after restart. Waiting for the code to return, as I have borrowed an improved OBD II that can do diagnostics.

 

[BabeGTR]

Update: After repairing the wiring into the #5 coil, the CEL has not returned. It does however still mis-fire, but now it takes a couple of hot starts to return.