Misfiring 5 cylinders After Overheat M54

[FerThewin]

Just bought an 01 Z3 2.5, with 130k miles. I'm a DIY'er for fun.


Previous owner overheated the car, then had it towed back. He said he turned off the car and towed it home, soon as he saw it was overheated. But doesn't know how long it was in the red for before he noticed. After he towed it back, it was running rough.. so I pulled the codes.


Car is now misfiring on 5 out of 6 cylinders


VIN Decoder says I have M54 Engine


P0300 - Random misfire
P1347 - Misfire Cylinder 3 with fuel cut off
P1351 - Misfire Cylinder 5 w/ f cut off


Pending
P1345 - Misfire Cylinder 2 w/ F cut off
P1349 - Misfire cylinder 4 w/ F cut off




Car runs really rough, and dies after 30 seconds of being started, unless you keep giving it a blip of the gas pedal.


I checked the spark plug wells, and there is no oil in them. I also checked one of the spark plugs, and it looks black and burnt to shit.. (Is it possible almost all the spark plugs went bad and started misfiring at same time?)


Coolant reservoir does not look milky, but smells like gas. Oil dipstick does not look milky.


Btw, I also sprayed all around the intake and vaccuum hoses with carb cleaner to see if I could find a vacuum leak but, no jump in revs when I was spraying around.


My question: Is it possible that this could be caused my something else besides a blown head? could something else have happened when he overheated the car?

[LannVouivre]

Well, if the plugs are worn you will need new ones anyway, so if you plan to keep the car you can give it a tuneup and see what happens.

I think it's a head gasket, possibly with warping of the head. Pull all the plugs. If the others are clean and shiny, coolant is getting in and steam cleaning the cylinders. Shine a flashlight down in there; if you are struck by the beautiful shine of the top of the piston, steam cleaning. (it should be a matte black surface from carbon). If the coolant level is dropping, but there's no sign of dried coolant on the hoses, water pump, radiator, or the pipe along the side of the block under the intake manifold, it's going somewhere else (note: use actual 50/50 coolant, water won't leave residue).

You can also run it briefly with the coolant cap off; if it fires out in a geyser or bubbles, exhaust gas is going into it. Lastly, get a kit to test for combustion gas in the coolant.

There's also always a chance you have a massive vacuum leak, but if the coolant smells gas...

[Mr Bingley]

Uh, time for a compression test.

[rf900rkw]

So he shut it off as soon as he saw the red light, give or take half an hour....


None of your tests are conclusive. A leakdown test with a real leakdown tester is in order (100psi, not the HF 20psi one). Have the expansion tank cap removed, and wear a rain suit. Then you pull the head and if you're lucky it's only a blown head gasket. But I suspect this critter was run out of coolant and driven until the problem was impossible to ignore.... and you'll find the threads pulling out of the head bolt holes in the block.

[gmushial]

Just bought an 01 Z3 2.5, with 130k miles. I'm a DIY'er for fun.

Previous owner overheated the car, then had it towed back. He said he turned off the car and towed it home, soon as he saw it was overheated. But doesn't know how long it was in the red for before he noticed. After he towed it back, it was running rough.. so I pulled the codes. ....

From Sun Tzu's Art of War: security is defined as knowing where the exits are, before you need them... I'd start searching the junk yards for a 2.5L M54 motor... yes, it might just be burned plugs... but I'm guessing you'll be doing an engine swap :-( ... do the leak down test, and go from there...

[FerThewin]

Okay so update

I pulled all 6 plugs, and I ran a leakdown test.

Cylinder 1 Leaks air into cylinder 2, Cylinder 2 leaks air into cylinder 1 and 3, and cylinder 3 leaks air into cylinder 2 and 4. Basically all the cylinders are leaking air into eachother.


When I ran the leak down test, I topped up the coolant reservoir. When I ran the air pressure into the cylinder, the water started overflowing in very small amounts and very slowly from the expansion tank


Also, I ran this leak down test while the engine was cold (No way I can warm engine up enough for it to be hot, ran really rough.


Now my guess is leaning towards Warped head due to all the cylinders leaking air into each other.

[rf900rkw]

I'd say the results are pretty definitive.

[gmushial]

Okay so update

I pulled all 6 plugs, and I ran a leakdown test.

Cylinder 1 Leaks air into cylinder 2, Cylinder 2 leaks air into cylinder 1 and 3, and cylinder 3 leaks air into cylinder 2 and 4. Basically all the cylinders are leaking air into eachother.


When I ran the leak down test, I topped up the coolant reservoir. When I ran the air pressure into the cylinder, the water started overflowing in very small amounts and very slowly from the expansion tank


Also, I ran this leak down test while the engine was cold (No way I can warm engine up enough for it to be hot, ran really rough.


Now my guess is leaning towards Warped head due to all the cylinders leaking air into each other.

Or combination of warp, and cracks?

[rf900rkw]

When they crack, it's from a water galley into an exhaust port at/near the seat. That's where the heat concentrates. Cross leaks between the cylinders could be caused by not having the engine in the correct position for the test. But the coolant level rising is enough evidence to pull the head.

[gmushial]

When they crack, it's from a water galley into an exhaust port at/near the seat. That's where the heat concentrates. Cross leaks between the cylinders could be caused by not having the engine in the correct position for the test. But the coolant level rising is enough evidence to pull the head.

From your experience: when one has such a seemingly pathological case, where it appears the head gasket is not sealing "anywhere": what are the chances that the deck is also no longer planar, ie, one can replace the head, but given the deck, a new gasket isn't going to be able seal anyways, given a lack of support from the bottom side? ... that's the genesis of my comment about seeking a junkyard motor, ie, to have done that much damage, one has likely done other damage beyond the head.. and if one does have to go the replace the motor route, the time removing the head is essentially wasted, and would be better spent removing the whole shooting match. .... my real question is: relative to the head: how robust are the blocks?

Now I clearly understand the "let's see what we can do" approach: when they said I had 44 breaks in the various bones in my right foot, and that the easy way out was to simply amputate it, as in to try to mend all the damage: a) would take months if at all successful; but b) in all reality is unlikely to be successful... my reply was: we'll give it a try, and if that fails, then we'll look at other options... four decades later that foot walked the PCT from Mexico to Canada in just over five months...

[rf900rkw]

If things got hot enough, the head bolt threads won't hold when he goes to torque it down. On suspect motors, I'll break loose the bolts then run through a torque sequence before even lifting the head. I have repaired a few with Timeserts. I'm not saying the block can't warp, but it's not a weak point.

[FerThewin]

Going to pull the valve cover off today, and snug up the head bolts to check to see if any are stripped. Just waiting on my amazon delivery for headbolt socket!

Going to snug up the head bolts to see if they are stripped according to this video: https://www.youtube.com/watch?v=ZRnYhZFVvBY

Also, here are pics of sparkplugs, they look nasty. Some look wet? Not sure if gas, oil, or coolant.

Resized_20170621_171606 (1).jpeg

[Mr Bingley]

I would not describe those as particularly nasty looking plugs. The being said, you still have a blown head at the very least. I like that guy's video's--seems like a good test, and a useful fix option. Good luck and post the results.