Misfiring / Loosing Cylinder

[MerlinTheHapyPig]

I've just picked up a bare motor (rb20det), and apparently it was taken out of the car because it had developed a misfire / loosing a cylinder and the owner was going rb25det anyway.

my first thoughts would be that it would be a coil pack / ignitor / spark plug / injector or something that would cause this, my question is

Can something internal cause this sort of thing? I'm trying to ascertain if the motor itself is going to be ok, the guy i bought it off didn't bother taking the motor apart or doing a comp / leak down test or anything so im wondering if the engine might be ok, and it was actually an electrical problem, they tried changing coil packs and spark plugs but that was about as far as they got diagnosing.

I'm wondering

a) what can cause this sort of problem head/block wise?

b) if i pull apart the engine, what should i check for?

I've popped off the rocker covers and had a squiz, everything looks ok as far as i can see, if i can find a starter motor and flywheel i might try doing a compression test.

Any ideas would be great!

[nissan_280zx]

i would suggest you do a compression and leak down test, if that goes ok, I would check the valve train. If all seems to be good, i would be happy with that.

[Duncan]

As far as the motor iteslf goes the only missfire problem is compression related. Spark and Fuel are both from external systems.

So like nissan_280zx said all you can do is check compression. but its unlikely to be the cuase of the problem

[MerlinTheHapyPig]

awesome, thanks for the replies, that's exactly what i wanted to know.

posted same question on ns.com and everyone is going "check the coil packs", "check the ignitor".... no1 seemed to figure out that i was talking about the bare motor

Now i have to figure out how to crank the motor with no gearbox/flywheel, i might have to borrow some stuff from the local wrecker, or just wait till i blow a motor and have it all out of the car.

Has anyone done a comp test with engine out before? should i put oil in it to do the test?

[ODessA]

i had that problem with my rb20 was one coil pack died, its common problem apparently, get one that works and swap them around see if the miss goes away

[ODessA]

oh engine out of the car.

good luck to ya