Flunked Calif. Smog test

rlumbard1 · Post by **rlumbard1** » 25 Mar 2004, 22:42

Have 1986 240 DL 2.3LSOHC. I cannot get the nitrous oxide PPM down. I am at 1641 PPM. Max allowed is 1230. Odometer reading is 160,000. The car is stock with no mod

Volvord · Post by **Volvord** » 26 Mar 2004, 15:52

NOx emissions are directly related to high combustion temperatures. The reason your engine passed is that by increasing the timing the combustion temperatures are lowered.

Reasons for high combustion temperatures are: lean fuel mixture, late ignition timing, high combustion pressures (high compression). Some things to check and try would include: cleaning the injectors, dirty injectors will not atomize the fuel efficiently, this can cause incomplete fuel mixing and incomplete combustion which creates hot spots during combustion which increase NOx. Spark plugs too hot, try installing a colder range of spark plugs, this will reduce combustion temperatures and can reduce NOx, but can also increase HC. Carbon deposits in the combustion chambers can increase compression and reduce heat transfer into the cooling system, run some safe combustion chamber cleaner through the engine can reduce carbon deposits. Finally cam and ignition timing can be effected by an old or worn timing belt, although unlikely there could be enough ignition/cam retard from a stretched timing belt to have some effect on NOx.

Good luck

EL COYOTE · Post by **EL COYOTE** » 28 Mar 2005, 11:27

TRY REPLACING THE CATALYTIC CONVERTOR

Guest · Post by **Guest** » 28 Mar 2005, 13:12

The Catalytic converter reduces Hydrocarbon emmisions, it will not have any effect of NOx.

This post is also a year old, I am sure the cause of the problem was corrected

Carolynn · Post by **Carolynn** » 01 May 2005, 15:12

i have a really good friend where i used to live. He is known as the volvo doctor. when i got tired of failing every time i talked to him and he said put a tank of premium in it and run the crap out of it. Make sure when you take it in it is as hot as you can get it with out overheating it of course. I tried just idling it really high to get it hot but that didn't work. you have to actually drive it for a while then while you are waiting to get smoged keep it at high idle till they make you get out.