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[vrgsvette]

my 86 won't pass emissions here in Az. electical shop says everything is fine,yet O2 sensor is reading high sensor. the sensor is new, new MAF, most of the sensors have been replaced
the first reading were HC 00.36 good CO 003.64 GOOD NOx 04.09
the bad reading. these reading where also with headers on the car.
i put the original exhaust back on the readings went down, but th
NOx is still reading 3.47 which here in Az will not pass
thought maybe the headers where the problem with the O2 sensor. but it is still setting a high sensor reading

so if anybdy has any ideas i beg you please HELP

 

[69MyWay]

Are you getting the car good and warmed up before the test?

If you are less than 220 degrees when you go through, you risk failing.

How about the AIR pump and injection tubes? That is also the key to passsing. It pumps fresh air into the exhaust at the manifold and in the main cat. This injection of air causes a hotter burn, and it helps melt off the unburned fuel.

Many auto parts stores sell emissions tune fuel additives. Put Chevron brand high test fuel in, get the temp up, and add some emissions cure chemicals to the tank.

Oh, any chance you have a bad fuel pressure regulator? It could be leaking fuel through the vacuum line and causing the engine to run too rich.

 

[vrgsvette]

i was thinking maybe the air pump might not be any good, but the 02 sensor is reading high and the car remains in open loop
i drove it for about 20 miles before i got it tested the last time
and was in line for about 10min. besides my fan kicks on at about
220 so the car never funs the hot.
i will check to air pump maybe thats the problem thnx virg

 

[BigRed]

Sounds like Cat Converter to me. If the exhaust is running to fast ( through a gutted cat ) The O2 sensors will pick that up as lean and richen the fuel. Id suggest have your converter looked at.

 

[vrgsvette]

thanx for the post BigRed

 

[sidepipe]

Can't remember where I read it but some headers have the O2 sensor too far from the engine, not getting it hot enough. You might want to check with the header manufacture.

 

[vrgsvette]

i put the original exhaust back on it lowered the NOx
but not enough

 

[evolution]

Make sure you have a nice hot spark as well. New air filter and Shell/Chevron gas. That ARCO crap will kill ya OMHO.

Most likley AIR pump or CAT tho

Stupid emission crap.

"Me"--> :booty :dance <--"CA Smog Refs"
_

 

[sidepipe]

Just sitting here watching the snow fly and reading "Corvette Fuel Injection" by Charles Probst. A chart on pg 80, titled Rich/Lean Diagnosis, has some points you might look at. It states: Vehicle oper. indicates a lean mixture by high NOx, stumbles, stalls,surges,or poor performance. The chart references for this: Oxygen Sensor reads Rich (high O2 volts). The reason is Oxygen sensor being "tricked" rich. Causes are: Not enough air in exhaust. Check for: too much EGR/Oxygen sensor ground loose or dirty/no star washer (I assume on the O2 ground wire)/Oxygen sensor"poisoned". Hope this might help. Maybe a stuck EGR valve is all it is. Good Luck...

 

[sidepipe]

When you changed sensors, were the Engine Coolant Temperature (ECT) sensors included? They directly affect EGR....Don't give up.!!!..