96 Cat Monitor- Prevents smog
 

Just bought this 96 2.2 le, and i love it. Runs great but it wont pass pre-emissions smog test.

Its not throwing a check engine light, but the cat wont check complete on the pre-emissions test where it tests the evap, egr, 02 sensors, etc. Everything checks off complete but the cat.

I was told by the smog tech that there's a few options...

One, drive it more with BerryMans additive to get it hot (I drove it 1,200 miles after that; didn't work).

Two, replace the cat... YEAH RIGHT.

Three, take a chance on replacing the after cat o2 sensor. (Trying not to nickel and dime myself to death like i have in the past)

Four, plug the after cat o2 sensor and then drill and weld-in a new exhaust bung 8 inches lower than its original placement and he said that might work to check complete.

The smog emissions test equipment taps into the cars computer via the ODBII system.

It checks for trouble codes, trouble codes pending (a system has failed a self test but not enough times to set a code and trigger the check light) and completion of all self tests by the computer.

Typically in order to pass the smog test there cannot be any trouble codes, pending trouble codes and the self test process in theory must be complete. In theory because on some car makes and models the self test process is never fully completed due to the computer design.

It is possible all systems are working OK but the computer has just not finished with all the self tests. The smog station requirements may require all self test to be complete, if not the car fails the test as they don't understand the situation. The smog tech is just doing what they are told.

A mechanic or you can check for trouble codes that are set, pending codes (a system has failed but not enough times to set a code and turn on the check light) and if having the right equipment determine if the computer has completed all self testing.

If no codes or pending codes are found and but the computer has not completed all self checks then talk to the smog station manager. The EPA is allowing cars to pass smog checks with 1 or 2 systems tests still uncompleted as they realize some makes and model of cars may never complete these tests based on computer design. States have their own number of tests they allow to be incomplete but typically allow 1 test to still be incomplete and the car still pass. You need to address this to management as the smog tech may not know this and just be following the procedures that work for the majority of cars.

If you do check for codes and find codes or codes pending these need to be fixed before going any further into if the computer has completed all self tests or not. The car will not pass a smog test with codes set or pending codes.

Thankyou, but I pretty much already knew that. I just need to know what I have to do to make it check off. There is no check engine light or pending codes. The smog tech is my friend and owner, so if theres a way around anything he would know im sure. He did say that had to check complete or else he couldn't run it. He first suggested dropping the o2 sensor down the pipe 8 inches.

What state is the car being tested in?

Is the engine stock or has it been modified?

If stock it was designed to meet either Federal or California state emissions requirements without the engine or exhaust needing to be modified.

Suggest you get another opinion from a county or state government agency in charge of emissions testing.

California. And far as I know its stock.

Originally when I had got it, it was throwing an "insufficient air flow to egr" code. P240 i think it was. Anyway... Cleaned manifolds and replaced lines only to get to the "EGR Control Solenoid".

Its an $80 part with two choices. One for federal, one for california. I replaced it with the federal one (fed 1 plug, CA two) that it came with. It was registered in California and obviously smogged before so i figured that was a fine substitution. Check engine light went away, all was well till we figured the cat wouldn't check off. I hope this choice did not mess up how the cat works. My smog guy said no, but what do i know?

Your mechanic is also the smog test station?

As is, the Catalyst Monitoring Status flag did not reset. The shop told to drive the car with the gas additive in an attempt to reset the code but it did not reset.

The shop thinks it may be the converter but does not know. They also offered the other suggestions which may or may not help.

You replaced the EGR solenoid with the same configuration as the one on the car so all hoses reconnected to the same locations and the check light went off.

Note: There is a sticker under the hood stating if the car was built to California or Federal standards.

The engine computer has no direct way of checking the converters health. It does not monitor exhaust gases like a tail pipe test machine does.

02 sensor signal output responsed to amount of 02 in the exhaust gas.

The cars converter monitoring system has one 02 sensor installed in the tail pipe before and one after the converter. The computer compares the after converter sensor output with the before sensor output. If the after sensor output starts to mimic the before sensor output the computer "thinks" the converter is not doing its job.

Thus it could be converter OR something else such as O2 sensors. The shop can check the output from the 02 sensors with an ODBII reading device plus run a emissions tail pipe test to determine if the converter is working.

When ODBII checking was developed the EPA realized it was possible for a car to be in smog compliance but not all flags reset. They thus allowed 1 flag to remain unset for cars 2001 and newer. If California follows EPA guidelines they should allow 1 flag to remain unset and the car still pass emissions testing.

That is why suggested talking to someone who fully understands the states emission testing rules and regs.

FYI, if the car is built to federal emissions the federal converter price should be much lower then a California converter.