No spark on 2nd cylinder

[George]

I've been trying to figure out what is wrong with my engine.

Runs on 3 cylinders. When I pull the lead from second cylinder, nothing happens.

Spark plug is soaked in gas, so fuel is ok. Spark plug gives spark when pulled out and tested against ground while cranking.

Compression is ok on all 4 (145, 145, 159, 159 psi).

Tried changing sparkplugs, leads, nothing.

Tried switching the leads on the first coil (NB 1.6 engine, coil is basicaly the same as NA6 one) that operates cylinders no. 2 and 3 (should IMO move the problem to the 3rd cylinder and the engine should run since it's on wasted spark) but problem is still on second cylinder.

Any ideas?

1998 NB 1.6, MSII

[George]

tried a different coil pack, no change

[Satisaii]

Things that I would consider checking are too much fuel and weak spark. I know that anti-sieze on spark plugs can cause poor spark. The other thing that came to mind is a stuck injector. But I can't think of anything else that you have not already tried.

I don't know your testing method, tool you use, etc, but in our shop a 150 psi engine is ready to be replaced. It should still run good but won't make good power. Do a leak down test.

[—RotorNutFD3S—]

Without any other data, I'd agree with the likelihood of a stuck injector. Try moving the injector and seeing if the problem moves with it.

[George]

will do.

another new info is it runs on 3 cylinders only when idling, but runs on all 4 under load

[George]

moved the injector today, no change

[George]

continuity between injector connector and main relay/ecu connector checked and is fine

[MightyM]

My hunch is that it's your valves. Maybe broken?? But sounds like they're not letting the fuel burn if they're not opening properly. That's why your motor sounds like a stroked V8 ( on a miniature scale!) I had this same issue with my first miata, it was an NA6 with less than 100k miles on it. I dropped in a low milage JDM motor after I found out what as going on. Problem went away. If you run it while it's doing this for too long your exhaust will burn off/crack at the cat from all the extra fuel escaping into your exhaust manifold. This happened to me ON THE FREEWAY! My pipe was dangling, sparking all the way home... You will probably need to go through the head. Good time to do that head rebuild, port n polish.

[George]

hm... I have a spare, ported and polished head with exhintake ready somewhere... but it's no point doing this now I have 1.8 on the way

[MightyM]

Well, crack that head open after you have your new motor. I'm curious if indeed the valves are the issue.