Have a 89 Dodge van with 318 High HC emissions at low speed test. any ideas from those in the know.


Thanks in Advance

Sounds like fuel running rich! You have tune-up lately? plugs,wires, etc.

When you took the vehicle in did you drive it at least 20 miles to make sure it was hot enough,are did you go down the street and not warm it up.Temperature is a big factor in getting the catalytic convertors to do there job and burn off the excess emissions.if you did drive it far enough then i would suggest looking at the egr valve to make sure it is operating as designed.

change the oil, get it good and HOT(drive), and pull off a vacuum hose LOL!!! (just kidding)... in the old days, that would lean it out enough to pass it LOL!!!

stans advice is the best.

replace the catalytic converter

Why? If there's nothing wrong with it than he'll be wasting money.

no kidding... could just be a misfire on one cylinder. suprised someone would just start throwing $300 parts at it....

Your only 100 points off of the standard and if it was not hot enough when you took it in it will pass with no problems,after driving it awhile and making sure it has had time to get the cat to operating temp,i wish i was closer to you, because there are a few other little things that would take just a few minutes to check...but hard to explain how over the internet.Once again good luck...

exhaust converter controlls nox emmissions mainly. S.B. is correct your close. that is a primetive throttle body system. extra vacuum leak could help..

I do all of the emissions repairs at my shop. Catalytic converters are the most common failure I see. A good way to check it is to get the engine fully warmed up, drive it a few miles, and use an infrared thermometer to check the temp of the pipe coming into the converter and the temp coming out of the converter. The temp of the pipe coming out of the converter should be at least 100 degrees hotter than the inlet side. If the temp is close to the same, or colder, replace the converter.

Noxious emissions or "nox" as some people call them are reduced bu the EGR system.


On a different note---is the original poster stating that his HC's are at 318 or the motor is a 318?

well it would have to be 318 hc is the way i read it,i did not think they offered a v8 until later.

Check your air filter

In the full size van there was a v6 & a v8 option.

you are correct. it has been a long time. still no excuse for incorrect info.