CHARLOTTE, N.C. -- Joe Gibbs Racing officials are scrambling to uncover the cause of an unusually high number of engine issues during the first five races of the Sprint Cup season.
JGR had two issues this past weekend at Auto Club Speedway in California. The engine in Joey Logano's Toyota had to be replaced on Saturday when valve leakage was discovered following the final practice.
Denny Hamlin's engine failed 105 laps into the race due to an unrelated value train issue, leaving last year's Chase runner-up with a 39th-place finish that dropped him to 21st in points.
In all, JGR has had three engine failures in races and three more engines replaced prior to a race because problems arose. Last season, the organization had only two DNFs due to engine failure between Hamlin, Logano and Kyle Busch.
"Is there concern? Of course," said Jimmy Makar, JGR's senior vice president of race operations. "We've had a lot more issues than we'd like to see, this early in the season especially.
"Probably the bigger issue is for the most part they are non-related. That makes things harder to figure out. If you had the same thing happening over and over again you could focus on it."
Makar said only Hamlin's failure on Sunday showed signs of a potential bad part. He said the batch that the part came from would be quarantined for this weekend's race at Martinsville Speedway to see if any issues arise.
"It seems like every weekend there is something going on," Makar said. "It's very, very odd. We've been through cycles before where we've had valve springs and things that you come to expect to fail. We really haven't had these kinds of issues, certainly not this time of the year."
More alarming, Makar said there were very few changes made to the engines during the offseason. He said the organization purposely left things the way they were, with minor adjustments to improve fuel mileage that may have cost Hamlin the championship last season, before experimenting with new ideas.
"The few small changes we made you wouldn't have thought would have caused any of these problems," Makar said.
Hamlin's California engine was pulled and taken to Toyota Racing Development in Costa Mesa, Calif., as part of an agreement with TRD even though JGR builds its own engines.
TRD and JGR officials huddled over Hamlin's car for a long time after it was taken to the garage. Makar said JGR is working closely with TRD on the issues.
Richard Childress, the owner of Richard Childress Racing, said his Chevrolet organization likely would share what it learned from several engine issues earlier this year. Makar said it is not unusual for different manufacturers to do that when common engine components are involved.
Hamlin said the problems concern him because they impact his position in the standings.
"I'm worried a little bit more," said Hamlin, who had to have an engine replaced before one of the qualifying races at Daytona. "It's frustrating because you want to do the best you can each week ... and the team did a great job setting up the car and we had a fast car.
"It doesn't matter in the end if you can't finish the way you're supposed to."
Busch was the only JGR driver who didn't experience engine problems at California. He led a race-high 151 laps and appeared headed for victory before a late caution allowed Kevin Harvick to take the win.
But Busch had an engine failure at Las Vegas that left him 38th.
"That's the weird thing about it," Makar said. "You come with three engines, one blows up, one has other issues in practice and one comes back with no problems whatsoever. How do you make rhyme or reason with that? I wish it was an easy thing finding out what it is."
Makar also wishes he could guarantee this isn't a long-term problem.
"That's the million-dollar question," he said. "At this point, we still don't know. Every week it seems to be a different problem."
David Newton covers NASCAR for ESPN.com. He can be reached at firstname.lastname@example.org.