Private-equity firms that plunged headlong into subprime auto lending are discovering just how hard it might be to get out.

A Perella Weinberg Partners fund has been sitting on an IPO of Flagship Credit Acceptance for two years as bad loan write-offs push it into the red. Blackstone Group LP has struggled to make Exeter Finance profitable, despite sinking almost a half-billion dollars into the lender since 2011 and shaking up the C-suite multiple times. And Wall Street bankers in private say others would love to cash out too, but there’s currently no market for such exits.

In the years after the financial crisis, buyout firms poured billions into auto finance, angling for the big profits that come with offering high-interest loans to buyers with the weakest credit. At rates of 11% or more, there was plenty to be made as sales boomed. But now, with new car demand waning, they’ve found the intense competition -- and the lax underwriting standards it fostered -- are taking a toll on profits.