Ford Explorers are still making drivers sick, and it might be due to a faulty exhaust.

We last reported on issues surrounding the Ford Explorer in July of last year where complaints made to the NHTSA were mounting that drivers were being poisoned by carbon monoxide gas from SUVs exhaust. Ford has still not issued a full recall, and those complaints have continued to grow.

According to a new report from Bloomberg, there are now 3,000 official complaints to the traffic safety body for the model year 2010 to 2018 Ford Explorer. At issue is cabin carbon monoxide levels that experts are calling unsafe levels. One even said they were consistent with being in a house fire.

Police departments across the country are also reporting issues with their Ford Interceptor Utilities, which are based on the Ford Explorer. One complaint, which resulted in a lawsuit against Ford, saw the officer pass out behind the wheel, veered across several lanes of traffic, and then crash into a tree.

The NHTSA has been investigating since 2016, an unusual length of time due to the unusual nature of the issue. Carbon monoxide poisoning can be difficult to detect as most health professionals aren’t trained to test for it. There’s also no specific toxic level of carbon monoxide as poisoning can vary based on a person’s health and age.

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Making things even worse is the fact that most often the issue is sporadic. Bloomberg spoke to several people who have since placed carbon monoxide detectors in their Explorers and the detector only goes off occasionally to report an issue.

2017 Ford Explorer
via Ford

So far there are several theories. In 2017, Ford reported to the NHTSA that they believe the issue only occurs during full acceleration and when the Explorer’s AC is set to recirculate air. This causes negative air pressure inside the cabin that could suck in exhaust gases from outside the vehicle.

However, NHTSA documents indicate that Ford dealers reported cracks in the exhaust systems of at least 50 vehicles from built between 2011 and 2016.

Ford has instituted a program for Explorer owners since 2017 that allows for free inspection and repairs if they believe there to be a problem with the Explorer’s exhaust. It stops short of a full recall that experts and advocates are calling for.

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