No codes on this one, but it just came back from smog with High NO numbers. I'm guessing it is a bad O2 sensor, or is the cat dead? Oh, this is on a '91

EGR still working?

You probably knew this already, but NOx increases primarily as CC temps rise. It will also increase if the engine can't breathe. So, I think that Log1call's question is a good one. Plus, any chance you need to change the air filter?

I should mention, just checking for EGR trouble codes isn't really enough.

 

The exhaust passages can get blocked with carbon and the valves can get stuck closed with the same build-up over time. To make sure it's actualy working you need to dismantle the valve and blow air through the passages to check they are clear and inspect/decarbonise the EGR valve.

No EGR on 91 I believe. I own one and had problems with High NO a couple years ago. Basicly , if the engine is running lean and CC temps rise, the HC and CO go way down but NO goes way up....so IF the air filter is a little dirty or you can some how get your test run when engine is not super hot. I thought I was doing good to change plugs, air filter etc. to make sure engine was running well, it was doing well. I ran some RXP thru it and some seafoam and it got below the limit on retest. Subsequent years tests have been done on 2 speed idle that doesnt measure NO as they assume it is a AWD car(its not) and wont run on dyno.

Thanks. this is not my personal car and she will be retesting on Monday. I swapped out the O2 sensor and ran Seafoam through it.

Hey Subaru enthusiasts - a couple of questions regarding rear differentials. Are any later Outback rear differentials, 2000 and beyond, interchangeable with my 96? Also, what is locking verses non-locking. Will have to replace mine soon.

Hey Subaru enthusiasts - a couple of questions regarding rear differentials. Are any later Outback rear differentials, 2000 and beyond, interchangeable with my 96? Also, what is locking verses non-locking. Will have to replace mine soon.

 

since you are new i figure you didn't know it is considered rude to hijack some one's thread. you can start a hew one. the new thred button is visible near the top of the page with the listing of the posts. not visible when reading a post.

 

but i have already started on for you.

 

welcome aboard.