EA82 MPFI engine knocking noise.

[NorthWet]

1988 XT w/EA82 MPFI, led a tough life. In addition to the TOD from one of its HLAs that comes and goes, I have a knocking/rapping sound that seems to occur during light throttle cruise (maybe 10-20% power) and seems louder around 3krpm (maybe higher). Reducing throttle to engine overrun causes the sound to go away (or at least become inaudible) as does increasing power above 30% or so.

 

My first thought was piston pin knock, but I hadn't heard any talk about that before on the EA82s. Another thought was a vibrating engine whacking itself in to things on partial throttle (eg - loose engine mounts slamming home), but I haven't found any sign of stuff like that. Another wild thought was a loose flywheel, knocking on its mount bolts.

 

I am having auditory issues, so it is currently impractical for me to try to track down the location of the sound with stick/tube/stethoscope.

 

Oh, Intelligent Ones! (and you know who you are), is my engine about to ventilate its engine case due to "boredom of the con-rod"?

[NorthWet]

Well, Monday morning the noise got worse very rapidly, and I shut the engine down with perhaps 30 seconds left before something hand-grenaded. When I have the time, I will pull the engine out and do a tech-cropsy on it.

 

I don't know if I will just slap together another straight MPFI engine or start my high-compression turbo build. Money and time points to the former :-(

 

Until then, I'll have to drive my SVX instead...

[idosubaru]

i would have guess something less ominous like a bearing going out in a timing pulley or loose flexplate, but this sounds bad.

[NorthWet]

Thanks for the response, Gary. Funniest thing is that this noise has been occurring for 4-5 months, and right after I post about it things go really sour really quickly.

 

Ancient memories from autoshop say that tapping/knocking noises under no/low load means piston-pin issues, but never heard of those issues on the Subarus.

 

The other thought of the Flywheel coming loose scared the excrement out of me when the sound suddenly started getting louder and more easily right before I shut it down... even with with flywheel a foot or two if front of my feet, it would not have been pretty. Won't be able to dig in to the engine until after they MRI my head, and no clue when they will bother to get around to that.

[NorthWet]

Finally disassembled the engine enough to have a good look, and it tums out I spun rear-most rod bearing. Munched the crank journal, so I guess no quick-and-dirty fix with this short-block.

 

Well, I have its pistons, and I have a good turbo short block, so I guess it is piston swap time. BTW, This is the first time that I have messed with the internals of the short-block, and although I did not see any direction on how to remove pistons (or rods) without spitting the case, it is possible and not all that hard.

[idosubaru]

good luck pat.

 

i've spun a bearing before too on an EA - car was run low on oil and later in life locked up. EA82's don't typically do that without a reason.

 

i know it doesn't seem like it, but with unabused internals the EA82 can be a cheap and reliable engine, i promise. not much more than that, but it can do that!