We have a 99 Honda Passport, its misfiring, theres a popping noise in the air intake, no power, and the exhaust sounds muffled. We put brand new spark plugs in it and it did no good. Any ideas?

 

welcome to the forum. If there is a popping noise in the air intake, take a compression check of that cylinder and with the airfilter off, you may hear air coming through the intake valve. possible burnt valve or damaged.