A note of warning on the big rally

After sifting through the latest company results and a solid market rally, the question is now: Where does this leave us?

Could this market have some great legs to continue on the upward trend, or should we proceed cautiously?

Jim Cramer says that while Wednesday's rally is a great sign, as it shows that when the market gets oversold the buyers will bounce back, it could still be a one-day wonder. Investors should be prepared for a roller coaster ride.

Investors wiped the sweat from their brow when the Federal Reserve announced on Wednesday that they would not hike interest rates until the economy could handle it. But Cramer notes that this is a short-lived relief as the Fed cannot control the tanking price of oil or fear of Ebola that is worrying investors.

"The problems many companies are facing right now are beyond the purview of the Fed," Cramer added.

Read MoreCramer's wonder of the one day rally

Mad Money
Adam Jeffery | CNBC

Cramer also turned to Ed Ponsi, Managing Director of Barchetta Capital Management to take a strategic look at the charts. Ponsi looked at such examples as Monsanto,which provided a weak outlook and has recently shown such bearish patterns as the death cross and head and shoulders pattern.

Cramer added that "while I think it's a mistake to get too negative, we do need to get comfortable with the idea that the averages could still have further to fall here, and some of the market's former leaders may truly be stumbling and giving back their hard-fought gains."

One stock that Cramer believes could see amazing turnaround is GNC Holdings (GNC). Though Cramer does not expect strong results when the company reports in two weeks, he does think that the stock could skyrocket if they embrace his proposed structure realignment to refranchise its stores and repurchase its stock. If they don't do it, then someone else will. Which means it's worth buying into weakness in this case.

Read MoreCramer: Troubled charts mean stormy seas ahead?

In order get investor money back on track, Cramer said it will take some great earnings to be released. "I do not think anything other than earnings will determine whether this rally continues, and Alcoa suggests there are some legs to this rally," he added.

Alcoa (AA) earnings released on Wednesday after the bell provide valuable insight for investors, and this quarter is no exception. CEO Klaus Kleinfeld told the "Mad Money" host on Wednesday,"we are in quite a number of healthy and rebounding end markets; And I don't think Europe is quite as bad as so many people describe it." All in all, Cramer is bullish for the long term on Alcoa.

Read MoreAlcoa lifts Cramer from 'orb of gloom'

So with America the great kicking into gear, what ever happened to the promise of natural gas replacing oil-based gasoline and diesel? There are four reasons why.

First, regular engines have gotten cleaner. Second, the price of gasoline had to go higher to make the technology required viable. Third, natural gas has held up in price versus oil lately. And reason No. 4, the payback for these engines just isn't there.

Unfortunately, the competition is getting tougher for natural gas vehicles by the day, which is causing Cramer to suspect lower gasoline prices will put a stop to the development of this technology.

The "Mad Money" host continued to issue caution in the Lightning Round, but did mention a few winners. Windstream (WIN), Cramer said this stock is played out, Hertz Global (HTZ): The industry turned down, but he thinks there is still some great value, followed by Plug Power (PLUG): "I'm not a fan" said Cramer. "There's a lot of hype, here.If you have profits, I'd take them"