Changed Valve Cover Gaskets now misfiring

[MarkBlack]

I have a 1997 3.4L


I decided to change the valve cover gaskets and after doing so I have 3 cylinders miss firing. All on one side. I checked the connection, I checked the plugs, I checked the coils, and everything is fine.


My compression up until this point was fine. I had no issues with the motor.

The only thing left to check is the fuel injectors?

I'm so confused and stumped at this point. Has this happened to anyone?

all input is greatly appreciated. Thank you!!

 

[Skulking]

I assume you have pulled codes showing 3 cylinders misfiring? Which side is the misfire on? Will the 3 cylinders in the problem bank fire at all or do you only have 3 firing cylinders?

I think a fuel issue is the most likely cause of your problem, but before I look at injectors specifically, I'd look upstream and check the fuel rail and its connections. From the behavior you have described it's more likely to be an issue with something all 3 cylinders have in common rather than 3 separate components failing at the same time. I can't think of anything else where a single reassembly issue/ component failure would take out 3 cylinders. Everything else I can think of would either be one cylinder, two cylinders, or all six cylinders.

 

[TheLincolnGreen]

Misfire

Are you 100% sure you haven't crossed the plug wires?

 

[brillo_76]

Was it the wire side or the coil size? Its also possible if wire side the wires broke down after being moved around if they are very old.

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[TheDurk]

Are you 100% sure you haven't crossed the plug wires?

That's my vote. Check against this:

 

[MarkBlack]

Was it the wire side or the coil size? Its also possible if wire side the wires broke down after being moved around if they are very old.


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It’s the wire side. I also changed the spark plug wire set. That was the first thing I thought about

 

[MarkBlack]

That's my vote. Check against this:

I checked and I even replaced the wires.

 

[MarkBlack]

It’s the wire side. I also changed the spark plug wire set. That was the first thing I thought about

I assume you have pulled codes showing 3 cylinders misfiring? Which side is the misfire on? Will the 3 cylinders in the problem bank fire at all or do you only have 3 firing cylinders?

I think a fuel issue is the most likely cause of your problem, but before I look at injectors specifically, I'd look upstream and check the fuel rail and its connections. From the behavior you have described it's more likely to be an issue with something all 3 cylinders have in common rather than 3 separate components failing at the same time. I can't think of anything else where a single reassembly issue/ component failure would take out 3 cylinders. Everything else I can think of would either be one cylinder, two cylinders, or all six cylinders.

I ran codes and it is saying all 3 misfiring. It’s The side with 4,5,6.

Thanks for that I’ll check fuel rails next

 

[MarkBlack]

After further inspections I found a possible issue. I don’t remember if I un Hooked this hose, or it was like this. I googled some diagrams and it looks like the evap line?

 

[Skulking]

I ran codes and it is saying all 3 misfiring. It’s The side with 4,5,6.

Thanks for that I’ll check fuel rails next

I assume you mean 2, 4, 6 since 5 is on the other bank?

 

[MarkBlack]

I assume you mean 2, 4, 6 since 5 is on the other bank?

Correct!
Sorry spent 5 hours on this after work yesterday. Been long annoying day. Still trying to figure it out this morning

 

[MarkBlack]

Thank you to my fellow 4runner brothers! I’m not sure if I got a bad set of spark plug wires or what. But before I started ripping shit apart I went and got a new set of spark plug wires. The box I got was open so maybe it was broken and returned. But after double checking the diagram and a new set of wires it’s running like a champ!!

 

[brillo_76]

I have a thread for the resistance and the wiring diagrams with even the coil measurements. Sounds like someone put a junk set back in the box and returned them. I seen people return oil filters to walmart that were used before. I even got an open gallon of antifreeze once. I always verify the seals and filters before purchasing parts anymore.

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[Outrider]

Glad to read that you got it figured out. I have run into problems like this many times.

Reading down this thread, I also suspected crossed plug wires before I got to the end. To avoid that happening to me, I took a Sharpie and drew a firing diagram on my firewall, just behind the engine and near the top. To further prevent me from making a brain fart mistake, when replacing only plugs or wires, I always do only one at a time (if possible). Not possible to do when doing something like VC gaskets, but just a related tip from someone who often learns things the hard way.