Why is my Cylinder 2 Misfiring?

EDITED:
This problem is on and off. Sometimes the truck starts and runs perfectly strong.

I've replaced all of these and still am getting P0302, cylinder 2 misfire:

Spark plugs and wires
Distributor cap and rotor
Cleaned MAF sensor with CRC
Valve cover gasket
Spark plug tube seals
Changed Air Filter

Unrelated things I've done (but maybe something happened?):

Changed Front diff/rear diff and transfer case fluid
Changed brake fluid
Replaced the starter (that was the first thing to go after I bought the truck)

I am out of ideas. Its at the shop now and I am going to have them run a compression test. If cylinder 2 has low compression is that an indicator that the cylinder is bad and there is no fixing it? Or are there a number of things that can be fixed to restore compression and get the engine running well again.

Also, here are images of my engine with valve cover off. Anyone know what those white markings are?

 

How many miles on the engine? When was the last time you had the valves adjusted? I would start with cleaning everything, new VC gasket. I would also clean the MAF sensor and reset the ECU. Then go from there.

 

Check engine compression, the best way to find out if cylinder is bad

 

136k on the engine. I just bought the truck about 3,000 miles ago though. It has run great up until this past week. I’m not a mechanic so it seems the Valve Cover Gasket may be a job out of my league. How do I reset the ECU? I can also clean the MAss Airflow Sensor, so I’ll do those two things for sure.

 

If a cylinder is bad, that essentially means the truck would need a new engine?

 

Ok, just checked distributor cap and rotor, seems that everything is fine. Would this mean that there may be an issue with the cylinder or are there still a number of electrical components I should check before paying to have a compression test?

 

Also, if a cylinder we're bad, wouldn't the cylinder consistently be misfiring? As opposed to this on and off. Because it runs perfectly when I'm not getting the code, but every now and again it happens. Started the truck up this morning and drove it to work. Drove just fine.

 

My 2rz stuck a intake valve on cyl #1. Caused a terrible misfire. Truck wouldnt even idle. Def check compression. But if its intermitent its likely not an issue. Still check it though so you cover your bases.

 

if the misfiring isnt continuous then its not a big of a problem yet. But it can definitely lead to one. reset the ecu, change the vc gaskets.(so you wont have oil all over your engine or in spark plugs).if that doesnt work, best bet is get it checked out by dealers. either way you will end up spending money might as well make it count.

 

How do I reset the ECU? I'll do some researching on this and figure it out.

So do you think that's definitely a VC gasket leak? I do the majority of the work needed myself, that said the VC gaskets seem to be a pretty big job with lots of room for serious error. But, from my research it seems as simple as taking all attached components off of VC and then replace gasket and then reassemble everything the way it was. Am I being naive or is there much more to it?

Thanks for all of the help.

 

just disconnect the negative terminal from battery for good 15-20mins. that should take care of ecu. for vc gasket, it looks big job but it actually isnt. take off the intake, disconnect maf sensor, remove all the screw that are attching VC to the engine and it comes eight off. just make sure you clean all the old rtv from both sides before putting on new gasket.dont forget to use rtv with it and dont forget to replace the small gasket for spark plug holes.

 

Nice, thanks for that. I think I'll definitely do that myself then after some more research. From the photos, would you say that it's most likely coming from the VC gasket? I don't really know what else would cause oil build up right there.

 

im 98% sure its the valve cover gasket. theres nothing else up there that would make the oil leak.

 

I think a good cleaning of the MAF and cleaning up all that oil on top should do the trick. Once it starts sounding like a Subaru you know you have a dead cylinder. You can quickly verify by pulling the spark plug wire and if you notice no change then that cylinder is out. Then you can do a compression/leakdown test to verify. With over 125K miles I would start saving to have the valves adjusted.

 

Ok will do. I reset the ECU and that didn’t fix it, so next I’ll clean the MAF sensor. I don’t believe there’s a bad cylinder, sometimes it drives perfectly with no check engine light.

 

You need to reset the ECU after you clean the MAF.

 

Cleaned the MAF sensor with CRC cleaner. I also took off the valve cover and replaced the gasket along with the spark plug tube seals. Drove it today. Went about 100 miles perfectly, drove really well. Then boom, out of nowhere I get a cylinder 2 misfire again. Code P0302

Not sure what to do next? I’ve already replaced:

Spark plugs and wires
Distributor cap and rotor
VCG and spark plug tube seals
Cleaned MAF sensor
Air filter
Ran injector cleaner through the tank

Should I go onto fuel components like fuel filter or fuel injectors? Could this cause misfire?

 

you can simple check fuel injectors using a long screwdriver. just place the screw driver on top of metal part of fuel injector while yhe engine is running and hear for rapid ticking noise. if that ticking is there, the injectors are good.

 

for fuel theres nothing much to check. just check fuel filter, fuel pump and fuel pressure. if all 3 are there and injectors are working good, then your problem is not related to fuel.
check fuel pressure first. if you are getting good fuel pressure then the fuel pump and fuel filter gotta be working good.

 

Ok, thanks. Its at the shop right now, they're going to see if they can get the misfire to happen and then diagnose accordingly. If they can't figure it out then I'll check fuel pressure and injectors. Probably just going to have them do a compression test and see if cylinder 2 has enough.

So strange that it's happening so intermittently. If it we're a fuel component, I feel like it would be happening continuously and not this on and off kind of problem? Maybe not though, I'm out of ideas.