Bert Jones struck fear into the hearts of the Pittsburgh Steelers today with his impetuous running but sabotaged himself with his impulsive right arm and the Baltimore Colts were left to marvel at the poise of the Super Bowl champions.

For the second week in a row, Steeler strong safety Donnie Shell stopped an opponent's rally with an interception and the Steelers (2-0) escaped with a 20-17 squeaker.

The Steelers had regained the lead at 20-17 on a 24-yard touchdown pass from Terry Bradshaw to wide receiver Jim Smith before Jones took the Colts 64 yards to the Pittsburg three-yard line, the last 11 on a powerful, nifty run. But a groan greeted the official's flag, signaling holding by guard John Pratt on the first down and putting the ball back to the 13-yard line.

No problem. Jones was having one of his best days, a preinjury performance. He shot a quick pattern pass to wide receiver Ray Butler. But Shell read the quarterback's mind.

"He had only thrown the very same pass seven or eight time," Shell said.

"I think it has to do with maturity," said Shell, a seven-year veteran. "We have a lot of guys here who've been playing five or six years together. We know what's happening and we know what to do when we have to do it."

"They threw it right in my hands," Shell said of the interception. "I think Bert may have expected a man-to-man coverage. We are playing a zone." "I shouldn't have thrown the ball when I saw Shell hanging back," Jones said. "I blew it. I lost the game."

Coach Mike McCormick of the Colts put it another way. "We could have, we should have won the game, but 'could have, should have' are words for losers.The Steelers dropped off, Jack Lambert stuffed our tight end. World champions will do that.

"We put a little fear into the Steelers and that's all you can expect. I'm proud of our players, except for some mistakes and penalties. The defense did a good job."

Pittsburg Coach Chuck Noll said: "Baltimore played an exceptional football game, but our team showed a lot by coming up with the big play -- like Donnie Shell's interception."

The Colts for a bad break that amounted to the three-point difference between the teams when a 46-yard field goal attempt by Steve Mike-Mayer in the second quarter hit the right upright of the goal and bounced off to the right.

"You've got to expect that," McCormack said. "We had enough to win the game."

Shell's interception came with 3:30 remaining and Bradshaw killed the clock with the help of runs by Sidney Thornton and Greg Hawthorne for first downs.

Earlier, the Steelers settled for field goals for 25 and 29 yards by Matt Bahr before Bradshaw forced a throw that would have been the subject of a second guess had the Steelers lost.

A safety blitz by Nesby Glasgow of the Colts hurried the throw by Bradshaw, with Glasgow's upraised hand obstructing the quarterback's vision. Linebacker Sanders Shiver intercepted and ran the ball 34 yards for a touchdown and a 7-6 lead in the second quarter.

But the Colt defense could not handle the Steelers' big-back offense.

Franco Harris, 30, ran for 40 yards and caught six passes for 31 yards in the first half; Thornton ran for 40 yards and caught three passes for 21 yards.

The Steelers went ahead, 13-7, in the second quarter on an 87-yard push, during which Harris caught three throws, for five, 31 and, finally, 10 yards for a touchdown.

In the third quarter, Jones made the quick post pattern to wide receiver Butler work for a touchdown and a 14-13 advantage. Then the Steelers made two big mistakes that set up a 20-yard field goal by Mike-Mayer and a 17-13 lead for the Colts.

Linebacker Jack Ham took off rookie Curtis Dickey's helmet with a face-mask grab that cost 15 yards. Defensive tackle Joe Greene protested the call so demonstratively that 15 more yards were tacked on for unsportsmanlike conduct.

Jones passes 14 yards to wide receiver Roger Carr, went back to Carr and got the ball to the five-yard line when a personal foul was assessed against the Steelers on the play, moving the ball half the distance to the goal line.

But the Colts found out, as did the Houston Oilers last week, that it is difficult to run on the steelers and settled for Mike-Mayer's three-pointer.

Bradshaw switched from his running backs to his wide receivers as targets in the second half and a 24-yard touchdown thrown by Bradshaw to Jim Smith in the fourth quarter accounted for the 20-17 score created by Jones at the finish.