Hey guys my Q failed the Emissions portion of the CA Smog. I have no clue what made it fail. I just replaced the fuel pump and filter. The only thing I think it may be, is the the IAC Valve. There is a hose on the IAC Valve that doesn't look like it is completely connected and it doesn't have a clamp on it. Could that make it fail. Also the car starts to stumble only at low RPMs at around 15-25Mph. Can that be from the IAC also. HELP!!! I need some guidance.

What RPM range does the engine stumble at?

The testing station tells you what part of the test failed so post up the results.

Put that hose where it belongs with a clamp and see if you pass the (Useless) test.

IT failed the NO(PPM)
15 MPH Max:475 (677)
25 MPH Max:478 (773)

NO is always EGR related, as it is on every gasoline car on Earth!
Usually clogged [or partially clogged] passage system from lack of mainteance.

So Replace the EGR Valve? or clean it.

The carbon usually clogs the port in the plenum that's fed by the EGR valve. It's not unusual to find it nearly 100% plugged up with hard crusty carbon. The preferred method for cleaning it is to remove the plenum and clean the port with various brushes, drill bits, dental picks, brake parts cleaner, etc. You can probably clean it with the plenum in place if you remove the throttle body and figure out a way to get paper towels in there to catch all of the debris before it falls into the runners, but it would be tedious.

Heath

He could use a electric vacuum to prevent the crap from falling into the runners. But like Heath said if its really plugged up its far easier with the plenum off.

Hard dental tools often necessary, many times drill bits, or homemade roto rooter from a old piece of throttle cable splayed at end and battery drill. Depending on oil and air dirt the carbon can get harder than concrete.

Pictures should be taken for public display by name to prove the lack of cleanliness of many owners

Thanks guys, but will that solve the problem with it cutting out at low speeds? 15-25mph thats prob between like 1500-2500 Rpms, thats just a guess.

An EGR flow rate that is below spec would increase Nox.

Real quick lets cover some theory...

Oxides of Nitrogen are caused when combustion chamber temperatures increase beyond a specified level. The egr returns a small amount of exhaust gas into the intake stream in an effort to cool the combustion chamber temperatures. Egr flow only occurs under light to moderate load so under the conditions you are asking about would fit the criteria for an EGR flow function issue. If flow were restricted enough to cause you to fail an IM240 it really should have set a check engine light with a Egr function dtc.

While carbon deposits are very common (it is a cool running V8 after all) and some serious elbow grease will be needed to undo years grime this job is going to require a bunch of tools and about a weekends worth of work for a first timer.

You have to test the egr function. Following the directions in the EC-FE section of the FSM to verify operation of the egr system.

Well it just occurred to me that is the car stumbles at 25 mph, How the heck can the smog the car accurately?!?!?

evil_panda wrote:Well it just occurred to me that is the car stumbles at 25 mph, How the heck can the smog the car accurately?!?!?

yea the guy at the test station said, "your car was stumbling at around 25mph, but I got it to make it through the test"..I was so pissed that I ignored the main factor in the problem.