DENVER -- Many homeowners have discovered an offensive odor plaguing their front loading washing machine.

Appliance experts tell the Call7 Investigators they hear the complaints all the time, but try to spare customers the ugly truth about what exactly is causing the odor.

Many people try to get rid of it, but complain nothing works.

"I smell it now, uh huh," said Holly Burkett, as she makes a face opening her washer door.

The Burketts bought their high efficiency machine for all the right reasons.

"We wanted to do more laundry less often and so far we've been pretty pleased with that," she said, “It saves on water, that was a big selling point for us."

Burkett said the sour smell first set in a couple of years ago.

Now, it is starting to linger more and more often.

"Yes, I would call it a smelly washing machine," she said.

Burkett is not alone.

The problem has even been dubbed “smelly washer syndrome” by bloggers trying to solve the problem.

"All the sudden everyone's talking about it," Burkett said.

Call7 brought in the experts from Mr. Appliance to sniff out the problem.

"I understand you have an odor problem with your washing machine," said repair technician Robert Rappuchi.

"Yes, stinky odor coming out of there," Burkett said.

Rappuchi said he hears that complaint a lot.

He said there is a reason front loaders are vulnerable.

"The reason is because the tub is tipped over and the water seldom gets above one-quarter full and the outer tub is dry except for residue that's spun off the clothes," Rappuchi explained.

The residue builds up where people can not see it and water can not reach it.

"There's gonna be a slime, detergent build up, yes, and mold," he said, “I sometimes try not to let people see what's inside the machine."

But Burkett needs to know.

"So, Robert can you tell me exactly what's making my washer smell?” Burkett asked.

“It's actually mold that grows. Moisture can hang around," Rappuchi said.

"Ah, yuck!" said Burkett.

It is yucky, but fixable.

The first thing to do is make sure you are using an HE or high efficiency detergent.

Then, make sure you are not using too much.

"I recommend you start with 1 ounce of liquid or 1 tablespoon of powder and work up from there," said Rappuchi. "One thing you don't want to see is suds in your machine when it's washing." Leaving the washing machine door open to dry out will also help reduce the odor.

Appliance technicians recommend when all else fails, try a citric acid product.

Appliance stores carry bulk items for hot tubs that also work in washers and technicians often carry products on their trucks.

"If you do have an odor problem you use all three packets, then after that you can use one a month or two months," Rappuchi said.

Use hot water and run one tablet at a time through a full wash cycle to dissolve the build up.

To test if too much detergent could be to blame, run the washer empty on a rinse cycle. If there are suds, there is probably too much detergent being used.

Rappuchi said using chlorine bleach can also help cut down on germs.

Water temperature is also important. Rappuchi said detergent is not activated until water reaches 50 degrees, so he recommends a warm temperature setting.

He also recommends diluting fabric softener or stop using it altogether.