Car Rumbles 20miles After Radiator Flush, Needle up & down ~50 RPM Options

[tomazws]

As titled.

So what I did this morning:

Opened radiator cap, unscrewed bottom radiator plastic nob. Drained my Red Toyota 50/50 from radiator. Screwed plastic nob back into radiator and applied Prestone Radiator Flush, then fill radiator up with water (as shown by Prestone manual). Radiator cap on, started engine, heater up, ran for 10 minutes. Engine off. Radiator cap off, bottom plastic nob off, drained radiator. Scrwed plastic nob back on. Mixed 50% Prestone green poop with 50% water. Poured into radiator. Started engine. Air bubbles shown at radiator opening, poured in 50/50 till no bubbles shown. Put on radiator cap. Parked my car in street. Everything fine.

7 hours later, drove my car from San Gabriel to Rowland Heights (about 15~20 Miles), when car exited freeway and slowed down and eventually stopped at a light, I could feel my car rumbling, needles bouncing up and down 850 ~ 900 RPM, very not stable. After a short distance on local street, check engine light on. Stopped car, ran in house, turned on computer, Safari and 6gc.net, and here I am right now. Please help.