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Re: Smog, NOX too high
Posted by JohnB (more from JohnB) on Wed, 17 Dec 2003 04:54:25
In Reply to: Smog, NOX too high, Macy, Wed, 17 Dec 2003 01:02:06
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Sounds like lean. Vacuum leak somewhere or ecu isn't going into closed circuit at idle. You didn't say whether reading is idle or result of dyno test....I'm assuming idle ppm.
Recheck the throttle adjustment...it really isn't an adjustment per se...the throttle should be CLOSED at idle and adjusted thereto with the stop screw/locknut...closed as far as it goes and opened just enough that the throttle plate doesn't bind...it's supposed to completely block air through the throttle body when closed. Next, the idle switch should click immediately upon opening the throttle...you can hear it with engine off. If you can't hear it it's not adjusted correctly. And even if you can hear it, the idle switch may have failed...you need to check the continuity at idle, open off idle (or vice versa, it's supposed to change from closed to open).
Paradoxically, if you don't have enough fuel going to the cat it will read high nox...you have essentially zero CO which indicates not enough fuel.
And the 02 sensor is SUPPOSED to give the ecu the info to richen up the mixture at idle to stoichiometric...and it's not.
If the timing is excessively advanced you may have high nox. Dunno if 88 had crankshaft sensor/ecu controlled timing, so check the timing.
Lastly, check the emissions going into the cat. There is/should be a plug or you may have to drill a hole in the downpipe ahead of the cat to measure oxygen capture across the cat. It's possible the cat isn't doing it's nox job (takes a three way cat...did someone put in a two-way cat, HC/CO only?? Chances are your tech didn't put in a new saab cat...they're about $900 and a cats/R/us or somesuch is about $180!).
posted by 198.26.74...
Posts in this Thread:
- Smog, NOX too high, Macy, Wed, 17 Dec 2003 01:02:06
- Re: Smog, NOX too high, Macy, Thu, 18 Dec 2003 05:48:06
- retard timing a bit, JohnK, Wed, 17 Dec 2003 07:02:44
- Re: Smog, NOX too high, JohnB, Wed, 17 Dec 2003 04:54:25 <-- Viewing This Message
- Re: Smog, NOX too high, Baab
, Wed, 17 Dec 2003 04:52:51
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