18.1:1 AFR, help
18.1:1 AFR, help I did an exhaust gas analyzer on my 98 T/A about a week ago and the afr came back at a freakishly lean number of 18.1:1. how much power loss will that give me?? it feels like it is just not pulling like it should, and what could that be it is virtually stock, magnaflow exhaust, no cats, or rear o2 sensors, and a K&N fliter with free ram air mod. could the elimiation of the cats and rear o2 sensors be doing this, or is it something else, and like i asked before, what kind of power loss will being that lean create?? need help, thanks.
the readings were taken with a 4/5 gas analyzer, at the tailpipe @ idle, 1500rpm and 2500rpm. i am thinking it might be an exhaust leak. the previous owner had the exhaust welded on and there are like 6 or so welds from the manifolds all the way back. im thinking it is sucking in o2 somewhere in the system
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I've accually had REALLY bad results with taking a wideband further upstream and so did my buddy with his 02 Z06 and 92 stang S/C. We have both found out where the dyno dude puts it is the best place. We have had 2 different widebands and they did the same thing...reads all whacked out when O2 bung is further up in the exhaust. We made a clamp that holds the sensor one foot into the exhaust tip...perfect readings everytime. We run the wire into the trunk/hatch and up to the driver. Works perfect and there are NO worries of the clamp coming off at high speeds.
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Joined: Jan 2004
Posts: 33
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From: Colleyville, Tx
Originally Posted by 98RedBird
could the elimiation of the cats and rear o2 sensors be doing this, or is it something else
The rear O2's are ONLY there to make sure that the CAT is doing it's job. You dont need them, especially if you took the CAT out. Def NOT the problem.
I would agree with whoever said it, exhaust leak. But the leak would have to be after your O2 sensors. If it were before the sensors they would pick up that extra HC (hydracarbons) and CO2 (Carbon Dioxide) and adjust your A/F ratio accordingly and mask the problem.
The leak must be behind the O2's. You mentioned some welds that you weren't sure about, well that could defintly cause your supposed problem. Just so you know, your car isn't really running 18.1:1 thats just what is coming out your tailpipe. It's a great test if everything is in good working order.
How and if you repair is up to you! Good Luck. Keep us updated!
