QuestionMy 1998 4runner ltd (6cyl, 140k miles, calif), runs and idles fine but just failed a smog test. I had just replaced the spark plugs as a preventative measure, but the old ones looked pristine. I don't think I have ever seen the check engine light go on.
The readings @25mph were:
HC 7 (max 51), CO 0.0 (max .79), NO 2200 (max 765).
The mechanic thought it might be a bad (upstream) oxygen sensor, fooling the car into running lean. Does this seem reasonable? I saw your posts on the airflow sensor and planned to clean it as well.
I have a service manual and most tools needed to fix this, but before I dive in, I'd sure like to see those diagnostic codes so at least I can tell up front if I have really fixed something.
I tried using the E1-TE1 jumper, but I saw no activity on the check engine light so I guess this only works on ODB-I systems. Where the heck is the ODB-II connector on this car? My book says its just under the dash, but I suspect I need to remove part of the center console to see it.
If I can't borrow an ODB scan tool, I may have to check all the obvious sensors using the tests outlined in the manual.
Any advice is appreciated.
AnswerThere is an extremely high NOx reading as you know, this is always caused by the EGR system which was designed to reduce NOx emissions, with these readings the check engine light should be on telling you that the egr system has a malfunction, the OBDII connector is directly under the dash look to the right. If there is an autozone store nearby go there they will help you retreive any trouble codes in the system at no charge, if no autozone try Kragen or any other large auto parts chain store.
There is only one cause for high NOx readings and that is higher than normal combustion chamber temperatures or an EGR system malfunction, try to find out if there are any trouble codes in the computer and then get back to me.
