NA misfiring at high RPM, under load
 

I have an 87 NA motor that runs well in general, with some oil smoke at startup.

I'm trying to diagnose what I think is misfiring when I wind it out past 6k RPM or so...

When this happens, I lose some power, it feels rougher, and I can see some white/grey smoke being emitted. It happens intermittently, in quick succession, several times per second.

At first, I hoped it wasn't pinging, and I don't think it is because it doesn't appear to be damaging the motor, and I am N/A.

However, I noticed that it goes away if I pump a tank of 89 octane or higher gas. This is pretty strange, imo.

I also changed my plugs, with no effect.

I could have to do with the spark, shomehow, but I don't know why higher octane cures it.

Ideas?

Possibly dirty injectors?

Mine did that before I cleaned the injectors, so that could be it. But I also had a ton of other problems before...

Find an unused vacuum port on the engine. I found one on the passenger's side on the intake manifold. Get a long piece of hose, a gallon of water, and stick the hose in the water. Start the car, raise the idle to ~2500 to 3k. When the water is all gone, shut the car off, replace the hose, then start it again. Now, it will smoke white alot, but that's ok. It's steaming the carbon off the rotors, which is what I'm guessing is wrong with your car.

If you want the cheap way, that's it. I've used it, and it works just fine. Otherwise, take it to a shop for a full fuel system service, which gets you : 1)injectors cleaned 2)intake cleaned 3)Throttle body cleaned. It costs around $150 depending on what shop you take it to. I'd recommend a shop that uses BG or MOC products.