Slight missfire and ticking after a hard pull in 2nd gear.

[clongo]

So I finally got the car up and running well. This morning I was heading to cars and coffe and did a 2nd gear pull to just below 6k rpm's. I didn't notice anything odd after the pull until I slowed down and pulled into cars and coffee. I have a loud tick from the head and what sounds/feels like a very slight missfire. I also noticed that I'm now idling leaner than before.

I don't have time this weekend to pull the valve cover and check the valve train. I would imagine of I broke a rocker shaft it would be a very noticeable missfire. Anyone have any experience with a issue like this?

[mpowertech]

You dont have a boost controlled solenoid, right? Mine ticks pretty loud. Keep us posted

[m535is]

Killed an injector?

[Brad D.]

Broke a rocker arm? The lean AF reading is due to the misfire. The unburnt mixture shows up as lean due to the oxygen content.

[clongo]

Broke a rocker arm? The lean AF reading is due to the misfire. The unburnt mixture shows up as lean due to the oxygen content.

I'm really hoping its not a rocker. If your driving at speed it's hardly noticeable. But I can somewhat hear the miss through the exhaust note. Im going to pull the plugs and valve cover mon and see what's up. I just thought a broken rocker would be more noticeable.

[Shadow]

hey clongo.
I had a similar problem where it all of a sudden had a very loud tick at the back of the head.

Took the cover off and there was no apperent problems.
So maybe a month later I downshifted in 2nd from low speed 3rd and it instantly just STOPPED. Wierd. I have no idea what happened.

The car ran slightly leaner when it was ticking.

Maybe check if the cam on the rocker didn't slide off the valve.
That's something I thought about latter because the rocker is only held in place on the shaft by weak springs.

There was no felt difference in power though and I actually dynoed it that way (in my sig).

good luck.

[clongo]

Thanks shadow. Its running leaner at idle. But not excessively lean. Maybe 15.0 instead of 13.8ish. The miss is so slight that at first I thought it was me being paranoid. But it's definitely there. I'm going to pull the valve cover in the AM. My ticking is coming from the front of the head.

[clongo]

Rockers are all fine (thank god!)



Found cyl 3 exhaust lifter had worked its way really loose. Not sure how that happened since the nut is tight. Not the position of the hole on the eccentric. It's roughly 180 degrees out from where it should be. It has a ton of play in it.



Looks like I'll be doing a valve adjustment tomorrow after work. I'm just glad it's a easy fix!

[mpowertech]

[cvillebimmer]

Happy to hear its a simple fix!

[clongo]

Is this a common problem on M30's? Is there a way to prevent it from happening again?

[m535is]

So the nut was still tight but the eccentric had rotated? I personally would pull the stud and eccentric completely out and inspect it closely. I would also inspect the rocker really well for cracks and burrs. Basically there are 3 ways off the top of my head I can see this happening. First is that the stud is cross threaded or cracking therefore not giving the correct clamping load. The second is there was something preventing the eccentric from contacting the rocker properly, small piece of metal or whatever (burr), and eventually that came out and left the eccentric loose. Third would be that rocker is cracking in this area and not really holding fast, but I doubt this. Basically if it is cracking under the stud head then it could potentially not be holding well.

BTW, The only time I have heard about something like this is really short after a valve adjustment, but it was found that the nut was loose. Never heard this problem on a motor that had been running for some time.

[clongo]

I just put the head back on the car. I sent it off to the machinest and had it rebuilt. I doubt it even has 100 miles on it since its been back together. The nut may not be torqued right. I don't have a 10mm wrench here at the apt. I just checked the nut with my finger and it seemed tight.

[m535is]

I would say it probably wasn't torqued properly. I would pull the stud and check it anyway, but I would definitely be going through the head and checking everything.

[Jeremy]

I can't help with the slipped eccentric, but did the plugs all look good when you pulled them?

[clongo]

I didn't pull the plugs yet. I also don't have a spark plug socket here.

Having all of my tools locked up at the shop is a real PITA sometimes.

[Jeremy]

I didn't pull the plugs yet. I also don't have a spark plug socket here.

If your trunk toolset is present and complete, there's a spark plug tool in there.

[clongo]

Unfortunately its not complete. I'll just wait until tomorrow and bring the tools home.

[Brad D.]

Good news that it wasn't a broken rocker. It's odd that the adjustment changed the way it did though.

[FirstFives Dictator]

Good news that it wasn't a broken rocker. It's odd that the adjustment changed the way it did though.

Flat spot worn on eccentric?

[clongo]

I think I just left it loose. I double checked my valve adjustment and fixed the loose one. Everything is working fine so far.