Misfires After Valve Cover Gasket Replacement

[needmovies]

I have a 3.0 that I recently replaced the VC gaskets on and started getting misfires right after. I was wondering if you guys have some suggestions on what I should try next.

Just a quick background, I did my TB 2 years ago and replaced the VC gaskets as well as installed rubber heater hoses for the upper PCV hoses. Since then I've been having some slow oil leak on the passenger side. I finally decided to look into it two weeks ago, and found that the VC gasket was leaking slightly. So I decided to replace both passenger and driver side gaskets.

A couple days after the VC gasket install, I got a low oils warning and a CEL for misfires (p0300, 171, 352, 351, 301, 302). Checked under the hood again and found that the passenger side VC gasket is blown, and I have a huge puddle of oil in my garage. After further inspection, I found that the rubber PCV hose for the passenger side had a kink, which I though was probably preventing the pressure from getting relieved and eventually blew my new gasket.

So last weekend I replaced the passenger side VC gasket again, and redid the PCV hose by adding some 90 degree elbows to make sure it no longer has any kinks. I also went ahead and replaced the PCV valve, just in case. When I was redoing the VC gasket, I noticed some slight oil in cylinders 1 and 2, which would be consistent with my kinked PCV hose issue.

Got all of that done last night (had to wait for the PCV to arrive). I started the car and it idles really rough, as in I can feel the vibration on the seat. CEL is also flashing. I looked at the codes quick I remember p0300 is still on there and 301 at least, there's a couple more that I forgot to write down.


Any thoughts on what I might have messed up during the last VC gasket job?


On my way home today I'm planning on picking up some spark plugs. I will try wiping down the coils thoroughly in case they still have some residual oil, and I'll switch them around to check for bad coils. Anything else I can look into?


Thanks



tldr
- had passenger VC gasket leak so I replaced gasket
- newly replaced gasket blew + oil in cylinder 1 and 2 and misfire CEL
- found out PCV hose is kinked which probably caused pressure build up and blew gasket
- redid gasket and PCV hose + replaced PCV valve
- still getting misfires and rough idle



edit: are duralast (autozone) coil packs good? in case I need to replace mine. thanks

[SJorge3442]

hmm. Beware. All the 1.8 guys are gonna jump in here and say your misfires are from bad coil harnesses. I don't think I've heard of a 3.0 guy having that issue. Anyway, I would suggest starting with plugs and make sure they are gapped properly. I recommend copper plugs (NGJ bkr6e), just so you're not spending a ton of money to trouble shoot with iridium plugs. the coppers will only last 5k miles. I change them with each oil change.

if that doesnt fix the misfires, I'd start looking at the lower PCV line. The one that goes under the intake manifold. That could be gunked up causing PCV pressure issues. You can also test your PCV system/valve by trying to remove the oil cap when the engine is running. If there is vacuum, thats not good. It should be easy to remove if everything is working correctly.

[needmovies]

if that doesnt fix the misfires, I'd start looking at the lower PCV line. The one that goes under the intake manifold. That could be gunked up causing PCV pressure issues. You can also test your PCV system/valve by trying to remove the oil cap when the engine is running. If there is vacuum, thats not good. It should be easy to remove if everything is working correctly.

damn after our discussion from the PCV DIY thread, I was trying to avoid touching the lower PCV hose until next summer

I did try the oil cap test. I can easily remove the cap with no issues and I can feel a slight vacuum when I put my palm on it, which I think from what I read is normal.

[Furly]

You most likely just got oil on something or didn't plug something in all the way. As you said try to check the coil packs and plugs for oil and clean them up and check their overall condition. 3.0 are tanks and usually don't have fraying issues like a 1.8T that has a glowing hot turbo close to the wiring.

[SJorge3442]

damn after our discussion from the PCV DIY thread, I was trying to avoid touching the lower PCV hose until next summer

I did try the oil cap test. I can easily remove the cap with no issues and I can feel a slight vacuum when I put my palm on it, which I think from what I read is normal.

Its my understanding that if there is a broken PCV line, the system might display normal "oil cap test" symptoms. When I did my TB i broke a PCV line and it was noticeable on the first startup as I had a ton of misfires. Don't be scared about taking the manifold off. it truly isnt that complicated of a job. Just be careful with the alignment pins that are under the manifold. They generally break and end up in the intake ports of the head. Make sure you vacuum the ports to get all the chunks out as you don't want to miss anything.

[john_gonzo]

I second what these guys are saying for first steps: Clean and gap the plugs, clean the coilpacks, and make sure the coilpacks are seated in the head and the wire harness connectors are fully seated into the top of the coilpacks.

Also, you can try flexing the wiring harness slightly while the engine is running to see if misfires stop.

[cschuster]

So the valve cover leaked pretty much right after the TB was done? Check all the valve cover bolts, it doesn't take much to strip one. With 12 on each cover, its probably easy to forget to tighten one either. How about the PCV itself - was it replaced?

Maybe a major vacuum leak too. Check to make sure all the connections on the throttle body and brake booster are secure. Then look at the vacuum lines running from the back of the intake. I left my brake booster disconnected one time and almost shit myself when it started misfiring.

Unrelated to the oil leak, but have you tried unplugging the MAF to see if the car changes idle? If you unplug it and nothing happens, then the ECU isn't using that sensor because it is out of input range. Clean it with MAF cleaner and see what happens.

[needmovies]

problem fixed, thanks for the help guys

I started by wiping down all my spark plugs and coil packs, didn't help. I then replaced the spark plug on cylinder 1 and it ran normal again after that. not sure what happened there, maybe it got damaged when I pulled it out for the VC gasket or something, or maybe it was just time for it to get replaced

luckily it wasn't too bad


thanks again, you guys are very helpful as always