Hi Guys,
I tried to smog my car the other day and it didn't pass. I've listed my info below. Any ideas where to look on this?

87 Iroc 305 TPI
3 years ago new cat and egr valve

at 15 HC max-83, meas-82
at 25 HC max-61 , meas-63

at 15 NO max-541, meas-330
at 25 NO max-498, meas-870

 

What are all the gasses?

 

CO2 - 15mph meas-13.5 , 25mph meas 13.4
O2 - 15mph meas -1.4 , 25mph meas 1.9

 

What about CO?

 

My thoughts would be that during the three yrs since EGR replacement it has built up more carbon... Which can cause higher comb. temps which result in the higher nox. I would seafoam it if you havent. It lowered my nox n co when I failed. Plus added a new muffler since I had a stock one. It made a change.

 

Sorry,

CO - 15mph max .5 , meas .18
25mph max .41 meas 0.0

 

Did I lose you guys?

 

Any ideas?

 

Do the spark plugs,wires,distributor new or worn?Do oil change and retard the timing some

 

Do you think the oil would make a difference?
Thanks again

 

Yeah i would say so,engine has to work harder when oil is contaminated

 

Thanks. I've always used 20 / 50 oil on my high mile car. Recently my mechanic told me to use 10/30. What do you guys think? Over 200k mi.
Thanks

 

Is it burning oil?

 

It does go through some oil. Not super fast but I do have to add. Would the 20/50 make the engine work harder than the 10/30? That's what I was told. Which would be better for my situation with the high nox ?

 

Oil viscosity isn't going to make much difference to anything.

Burning oil could cause high HC, and high NOx could be a timing or EGR problem.

 

Check your o2 sensor too,might be time to replace and warm your car up good befote test