For anyone who can help, thank you in advance!!! I just bought an 88 LB9 T/A. I bought the car as is, it runs great! My problem is the previous owner failed the emissions test twice on hydrocarbons at 25 MPH. I figure an oil change, cap, rotor, and new wires will help, any suggestions? Or anyone had this problem before? I already changed the oil and added a fuel additive.

 

Might be the catalytic convertor or could be the smog pump air thermactor stuff isn't working properly. Get a haynes manual to diagnose some of those areas and if you can't take it to a shop and just get a diagnostic. But i think it's the catalytic convertor. How many miles?

 

Just take it in for a tune up and tell the mechanic that it has failed the smog test and they usually know what to check. It could also be the EGR valve.

 

I doubt it's the EGR valve. That typically affects NOx.

The cat may be the problem. A cheaper possibility is the O2 sensor. Replace it when you do the plugs.

Another possibility is a leaking injector (the fuel additive may help if that's what it is).

The fact that it only failed at 25 MPH is interesting, but the above 3 could do it.

 

Im goin in for smog this weekend..keeping my fingers crossed.....