Ok my car failed smog Its a 92 rs. I have replaced the egr valve with a new one from the chevy dealer. I have a new o2 sensor,rotor and cap, spark plugs, wires, fuel pump, fuel filter. mat sensor, oil switch sensor ,did an oil change 1000 miles ago. rebuilt tbi unit. new 3" car sound cat.New air filter. 180 brand new therostat.the timing is set at "0". the cars mods are. K&N air filter in stock unit edlebrock tes smog legal headers full 3" exhaust.stock chip. the car idles rough and serges in neutral. two shops have looked at it and they told me the computer isnt going into close loop. so i swaped it out and it didnt change a thing. i even tryed a new chip. Same problem. The exhaust smells really funky like to rich but the test said their was too much o2 in the exhaust. Their is only 145000 miles on my baby only 45000 on this motor .The tech also said the test points to a miss in the cylinder like its not getting a full combustion but the compresion test came back all the cylinders the exact same Im realllly tired of this anything would help. The shops tested everything,all sensors and fuel flow spark and it all checks out please anyone thanks for your help

 

I'd start with checking your plug wires with a ohmmeter. Also, run the engine with the hood up and look at the idling engine in the dark for arcing and sparking. Edelbrock tes headers are great for burning plug wires. If someone set out to design a set of headers guarranteed to burn plug wires with in one week of install, they would have made them tes's.

 

Nothing Changed? It Still surges in neutral.. I hope it can be figured out for you..

 

[too much o2 in the exhaust.]

Can you post what the rest of the smog test results are?

 

put the right thermostat in it (195).

is the timing supposed to be set at 0*? my 91 L98 calls for 6*. Are you setting the timing right? My 91 L98 requires the EST wire be unplugged to set the timing.

what mods have you done. (TB mods, cam, heads, anything else???)