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WTF going on with this engine?

apachechef

Burnt Sierra Madre
Joined
Jan 26, 2009
Location
An obscure body in the SK system
1993 240 LH2.4
Running great, begins to run roughly on highway(weak power,revving it smooth it, but rattle sound perhaps valvular origin?? when under load ,),pull over engine shakes hard back (4inches) and forth at idle, smooths out mostly with opening throttle. and revving it up.
pulling spark leads to cyl 1 and 2 does nothing, pull 3 or 4, engine dies.
changing plugs, plug wires, checking spark, seems 1 and 2 are sparking away just fine.

noid light on injector 1 and 2 flashes normally while engine is "running", engine won't start with the noid in 3 or 4, but flashes when cranking.
pulling leads off 1 or 2 does nothing, but 3 or 4 kills the engine.

pull rail, place injectors in bottles, connect the two ground wires back onto manifold.

crank the engine, get a little fuel in each bottle, and all 4 have equal amounts.

So, I'm thinking I have spark in 1 and 2, and fuel in 1 and 2, but removing spark plug leads or injector leads does not change rough idle
engine runs relatively smoother with opening the throttle and revving it up under no load, but IIRC loading it caused a valve like rattle and almost no power.
No obvious smoke from exhaust.

Diagnosis?

1 and 2 are not making power, despite fuel and spark, and the apparent "smoothening" with revving while parked could just be from 3+4 and enough speed being enough to not shake like at idle. that leaves valvetrain or compression?

tomorrow: compression test and borescopy?
Confused as to what would take out cyl 1 and 2.
Thanks
 
OH no! No way..You're doing it WRONG!!!!

THINK of the fawkin CHILDREN!!!!!!!!


leak down then compression.:oops:

I'm thinking perhaps either first would be wrong.
perhaps this test will not change outcome.
If the testing described above indicates a fix is not external to the engine, it is getting tossed in favor of a 2.5L beast waiting on a stand.

The problem engine is from an 1987, a temporary solution while I sorted all the fancy suspension stuff, now sorted.

despite not changing outcome, I am interested in a post mortem learning experience.

What do you think I'll find? two adjacent dead cyl sounds like a fuct headgasket betwixt them.

should I even bother with further testing, or let it run it's final drive to the adjacent garage stall and pull it and pop the head for a look before it gets dumped to the curb?
 
Well you know the two Johns are always giving an elbow to us in the ribs about how we should get the good rebuilt stuff in our cars. So I guess it is looking like an opportunity for what sounds like a fun engine in there.
 
Something more than just a gasket must have given up with two cylinders at zero. Maybe if it failed completely between them? Wish you well with the turbo shopping.
 
And if it was run for any length of time or at high power levels it has likely torched the head, block, or both.

If you rebuild make use of a Magnaflux before bothering to machine.
 
It?s a lot less labor to remove the head only with the engine in the car and see if the gasket is obviously blown between 2 holes :e-shrug:
Seen a couple like that where no coolant or oil were lost and/or mixed by now just finally let go on the most mundane boring B230F cars...

In my situation it's more work, the compression test was easy, and the engine is not worth putting a new gasket into.
 
Oscilloscope and inductive amp clamp over the battery cables=relative compression test=doing a compression test without even pulling the plugs.
 
8ozMo6H.jpg
 
That's incredible. By comparison, every failed head gasket I've ever seen was practically new!
 
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