Three of those errors came on one play in the first inning, allowing Detroit's Ian Kinsler to score from first on a walk. Then in the sixth, Angels catcher Hank Conger threw wildly to first trying to pick off Austin Jackson. It was his second error of the game, and Jackson went to second.
Nick Castellanos followed with an RBI single to put Detroit ahead 2-1.
Porcello (2-1) allowed a run and five hits, striking out four and walking one. Three relievers finished, with Joe Nathan pitching the ninth for his third save in five chances.
Hector Santiago (0-3) allowed two unearned runs and two hits in 5 2-3 innings. He walked five and struck out seven.
The Angels took a 1-0 lead in the first on an RBI single by Howie Kendrick, then let the Tigers tie it in the bottom of the inning in slapstick fashion.
Kinsler was on first and began running on a 3-2 pitch to Miguel Cabrera. It was ball four, but catcher Hank Conger threw to second anyway, and the ball sailed into center field. Kinsler went to third, and when center fielder Mike Trout's throw back to the infield missed the cutoff man, the Detroit runner tried to score.
It looked as if the Angels would have a play on Kinsler, but Santiago picked up the ball near the mound and threw wildly to the plate. Kinsler scored and Cabrera went to second.
Conger, Trout and Santiago were all charged with errors on the play.
Santiago threw 119 pitches and was wild throughout, but the Tigers never really solved him. He was lifted after walking Jackson with two outs in the sixth. Reliever Kevin Jepsen came in and was victimized by Conger's error and Castellanos' single.
Porcello was pitching exactly one year after allowing nine runs in two-thirds of an inning against the Angels - and he also gave up seven runs to Los Angeles in a start last June.
On Sunday, he allowed three straight singles in the first inning but kept the Angels quiet after that. Albert Pujols hit a first-inning single but remains at 498 homers as Los Angeles heads to Washington to play a three-game series against the Nationals.
Trout, who struck out four times Saturday, went hitless Sunday and grounded out with the tying run on second in the eighth.
NOTES: Kendrick had three hits. ... Rajai Davis and Alex Avila struck out three times each for Detroit. ... The Tigers begin a four-game series against the Chicago White Sox on Monday night. Detroit RHP Anibal Sanchez (0-1) faces Chicago LHP John Danks (1-0). Los Angeles RHP Garrett Richards (2-0) starts against Nationals RHP Tanner Roark (1-0).