Houbill

Background. 1993 5.0 LX CV. I have owned it two years. 60,000 miles now, I probably put 2000 miles on it the past two years, all town driving. Best I could research the mileage is true. Texas emission test. When I bought the car the Nox was 379, last year was 379. This year it was 1122 - failed. Limit is 796. I put in a can of Seafoam in the gas tank, probably 10 gallons in the tank. Took it out on the road, some 70 mph for 25 miles. Took it back for test - failed - Nox 990. I put in a new air filter prior to the second test. I really don't think there was anything wrong with the first filter (K&N)

Trying to research what to do. Spark plugs? I do not know if they are the original. Help to change? What is the accepted brand for the 5.0?. Should Seafoam be put directly into the air intake? How do you check for a vacuum leak?

I have a code reader. There are no trouble codes. Both the KOEO and the KOER tests pass.

I intend to pay the price and get a 'second opinion' of the test. Or else something bad has happened to go fron a reading of 379 for two years, then go 1122.

Ideas?

mjr46

I told you what to do here:
https://mustangforums.com/forum/5-0-...ions-test.html
and once you understang what produces NOX you'll see throwing an air filter at it was a waste as well as spark plugs......nox is a result of high combustion chamber temp,DUE to either a faulty egr system, carbon build up on pistons and or engine running hotter than normal due to an insufficient cooling system , seafoam it!!! brake booster works for this.