Having engine trouble, rough idle, no power, whats wrong?

I searched the archives and couldn't find anything similar to this...

A couple days ago I was cruising at about 65mph on the freeway and it started feel like the M30 engine was not firing on all 6 cyl. it started getting worse so I pulled off on the next exit.
As it slowed down it started to run really rough and barely stayed running, I managed to ease it into a parking lot and turned it off. I let it sit for a while then checked the vitals inside.

The oil looked fine, a little low, but no coolant visable.

The coolant expansion tank was empty, so I opened the tank cap and very slowly let the high pressure air out. Eventually the coolant returned to the tank from the system after it was depressurized, it seemed to be very near what level it was last time I checked it.

Then, I tried to start it up, but no crank. Oh-no! Fluid lock? Coolant in the cylinders...? Figured maybe a headgasket, but I don't see the coolant in the oil or vice versa. Well, I left it there and got a ride. Later that night it was towed home.

Finally, got a chance to look at it again last night. It turned over and started just fine...but after running for a bit I could tell something isn't right. Stepped on the gas and it seems to try to rev, but just bogs down like its flooding out.
Absolutely no power. It started running rough, so turned it off. No time to check anything else.

The last thing I did to the engine was put new bosch spark plugs it last weekend and it was running smooth as ever all week long. (gap: 0.7mm)

Anyone know whats wrong? or what do I need to check next? I'll have some time this weekend to look into it more. For now, I have to drive my gas guzzling Chev truck.

Thanks!

Have you pulled the valve cover to look at those components yet?

Maybe you just snapped a rocker arm or two. Dave has a writeup on that, IIRC.

Uberweird though, eh? Sounds like a fluid-related problem, but who knows until you go exploring.

best of luck!

best, whit

I'll pull the valve cover tonight and take a look.

Where is the write-up on that?

It sounds like fuel filter is clogged... maybe fuel pump on the way out.

I have a new fuel filter that I had planned to install soon. How can I test the fuel pump pressure?

However, it seems to be getting fuel just fine...
How would that explain inability to crank over after I turned the car off the first time?

Quote:

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Originally Posted by Tiger

It sounds like fuel filter is clogged... maybe fuel pump on the way out.

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check the battery, if its low or not charging properly it will miss and crap. Check the terminals and grounds and all that stuff for corrosion, sounds like electrical for sure if it wouldnt crank.

What do the plugs look like ?

If they are sheet white - you probably are loosing a fuel pump. You need to plumb a gauge inline where the fuel lines are, right below the intake on the driver's side. There is not tap, you will have to get a fuel pressure gauge and some brass fittings to make a t-assembly to monitor fuel pressure.

If they are black then you are loosing a coil or have a cap/rotor problem.

Finally got more time to look at it last night. Here is the run down:

Pulled Cylinder 1 plug, looked fine...
checked compression, it was about 160psi.

Next pulled #6 plug...hmm wet plug, and here comes coolant out of the cylinder, oh great...I think we dont need to do any further diagnosis, time to pull the head! Should I bother with checking all the compression #'s before I pull it? Now it'll be a bit harder since i've disconnected a few things already.

-The remaining plugs were dry except maybe #2 was a bit moist, not sure if it was coolant on that one.

-No coolant in the oil or oil in coolant so it must've blown between cyl #6 and a coolant path.

-In the archives somewhere it was stated that #6 was the most likely point of failure on the m30, so that seems to be the case here.

I've done the first few steps as per the Bentley manual...Anyone have any shortcuts or tips not mentioned in the book or at bwme34.net?

Do I need to take the exhaust manifolds off?

Thanks,