m20 cly #6 zero compression 1-5 fine

[colorado_cabrio]

Hey guys I'd love some advice on troubleshooting an issue:

Last week my 87 cabrio started exhibiting some concerning driveability issues; Loss of power, running rough (feels like a cylinder is missing), and white smoke (smells like oil vs coolant). No CEL, stomp test = 1444.

Pulled the plugs all were filthy, and all except #5 had fresh wet oil on them.

Ran a compression test and cylinders 1-5 all came back 140-145. #6 gave no reading (zero) re-ran the test a few rounds to check for user error or a bad thread seat but always 1-5 fine and #6 zero.

So bentley suggest that this is likely local head gasket failure arrounf cylinder #6 , but I'm worried about some valve-timing damage.

PO performed t-belt ~30k ago... But the condition of the plugs, and the end of the compression gauge show that there are some serious deposits in there so he clearly wasn't a stickler for oil changes.

So should I pull the valve cover? If I do what am I looking for? I'm a little confused on bentley refers to as the 'cylinder head gasket' vs what i assume is the valve cover gasket.

Any advice is really appreciated.

cheers
brent

[jlevie]

Pull the valve cover and take a look you might have broken rockers on cylinder six. If the rockers are okay, I'm going to say that you probably have a failed head gasket.

[nando]

pulling the valve cover takes 5 minutes.. so yes. I'd also be looking for a valve that's stuck open on #6, either from crud trapped in it or because it's bent.

[colorado_cabrio]

OHHH snap, I solved the riddle (the problem at least, not the root cause)

so I opened the valve cover and found this:
(sorry for crappy iPhone pic)



So the rocker on the driver side of cyl #6 isn't centered over the valve; it's shifted ~1" towards the rear of the car. So i scooted it back in place, buttoned up the engine and the car is back to itself. I'll run a compression again to see how that cyl stacks up later.

Now onto the root cause:
I know that the m20 is an interference engine, so maybe the timing belt stretched or slacked and the piston slapped that valve and knocked that rocker out of place?

Or is there another reason that a rocker might slip out of place? Do i need to do more than slide it back into place?

[dashboardmonkey]

find that missing retaining clip and replace it with another

[nando]

it's missing the clip. definitely replace it.. I wouldn't drive without it, you risk breaking the rocker and damaging the cam lobe.

[E-Thirty]

The clip looks like it's there, it's just leaning back towards the center.

[colorado_cabrio]

Yeah if the clip is the gold looking hoop that goes over the rocker, then it's still there; I pushed it back into place above the rocker.

And I'd like to replace it just tro be sure; but do I need to take out the rocker arm to do that, or do they somehow snap into place with the rocker arm already installed?

[e30rapidic]

no, if you look closely you will see 2 little grooves on the rocker shaft. The straight edges inside of the clip snap down into them.

you got lucky!

[colorado_cabrio]

I feel lucky!

Thanks to all for the advice.