vinniePOOH

iTrader: (34)

Im really not to familiar with reading smog sheet test. but this is how mines look like. So everything in my car is stock except for my DC stainless steel headers. apparently i passed the 15mph test but i dont know why the 25mph one didnt. So yesterday i just did a sea-foam treatment and while changing out the spark-plugs. The rear driver side plug had oil in it. soo my friend to me to replace the valve cover gaskets and the rubber gaskets that seals around the plugs/coils. I was wondering if this was a issue that would have failed me instead of my headers being aftermarket would have failed me. Any opinion or advice would be greatly appreciated!

F2CMaDMaXX

iTrader: (2)

It's possible that if you were burning enough oil then it would throw the reading, however, it's also possible the cat is fried on that side from oil going through, or just fried generally.

However, if i'm remembering this correctly, as the rest are in check and it's just HC's that are out, getting the car to clean burn again without the oil, replace the plugs and run some seafoam through the intake, take it for a drive, i think you might be able to pass afterwards.

That being the case, you should get better gas mileage too.

GGGVenom

What's the milage on the car? A defective CAT will cause high HC readings ..

btw .. my Z measured 12 at 15 mph and 13 at 25 mph ..

Neimad

Its running slightly rich and there is insufficient oxygen for complete combustion, either in the combustion chamber or the catalysts. Was it warmed up properly? Any Exhaust leaks before catalysts? Any codes pop up and go away recently?

I would have it retested first though, that station has poor performance for some reason:
http://www.bar.ca.gov/pubwebquery/st...spx?stn=265349

vinniePOOH

iTrader: (34)

Thanks guys..did the sea-foam treatment and changed out the spark-plugs but rear driver-side had oil in the camber. But idk if it was the reason for it to fail. Umm my Z had 90xxx miles n I was running TP than whiched it before the test.

Neimad

The oil just sits on the plug, it doesn't get into the combustion chamber. It might cause a slight bit of resistance to firing the plug and eventually the coil might fry but you would throw misfire code. The computer is probably all confused from running the test pipes. Also the cats if they were sitting for a long time might need to be broken back in. They are a honeycomb of three expensive elements. But looking at your numbers it looks like the fuel trim is off, and ideally the system should be throwing a code to make this easier. I would drive it for a week and see if anything pops up. If no codes run a pretest, see if there is any improvement. The seafoam is only going to help if you have so much carbon in the cylinders its absorbing the fuel before combustion, causing lean burn and then the HC's suck out unburnt when exhaust valve opens. But you have no NOX formation at the 25mph portion of the test so I doubt carbon buildup. Check the PCV valve for restrictions, you might have too much leftover combustion gases in the crankcase recirculating. Crappy PCV and valve cover baffles are why we get failed spark plug tube seals.

Bret86944

iTrader: (4)

How warm was the car? I know you can get crappy readings if the car isn't plenty warm. I'm talking like 10 to 15 minutes of driving around after the needle says the coolant is warm.

vinniePOOH

iTrader: (34)

Wow soo much stuff Im learning! Thanks guys..greatly appreciated! No codes popped up, my car was properly warmed up, and all spark plugs changed. I'm assuming that I did not let the car get adjusted with the change of going back to stock cats and stock air-intake. But no one has mentioned if running after-market would play a factor.

Neimad

If the battery was unplugged or ECM reset, ideally the fuel trim would adapt to the cats being there pretty quickly. It's possible a sensor is close to failing and the self-testing is unable to generate a code. Do you have access to an OBD scanner?

mr. sparco

iTrader: (13)

I had an issue with another car that was pretty heavily modded with high flow aftermarket cats. The smog guy was cool and said to make a few hard passes to really heat up the cat. After doing so it passed marginally.