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Bouncing AFRs

Old Feb 10, 2008 | 10:14 PM
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Default Bouncing AFRs

You can see on the graph here the AFRs bouncing from 11 to 13.

Any idea what could be causing this?
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Old Feb 10, 2008 | 10:34 PM
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looks like you have your O2 turned on in boost too
Old Feb 11, 2008 | 07:29 AM
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O2 turned on in boost?
Old Feb 11, 2008 | 08:37 AM
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Originally Posted by richard_ha
O2 turned on in boost?
running closed loop when in boost.

generally not a great idea as the response time of a WB sensor isn't as quick as a NB.

can be compensated for in the software iirc, but it still won't be perfect.
Old Feb 11, 2008 | 09:07 AM
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change your open-loop switch point to whatever (60-90kpa) or you have o2 sensor noise.
Old Feb 11, 2008 | 09:20 AM
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It is set to 90kPa already, isnt it?
Old Feb 11, 2008 | 09:29 AM
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I'm wondering if I've got a sticky injector or something. Look how rich this went (right to 8.9) after I did a 1/4 mile, even though the PW was 0
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Old Feb 11, 2008 | 11:28 AM
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OK, think I've figured it. The noise on the MAP is causing the acceleration and deceleration flags to get lit so it must be dumping fuel in for the acceleration enrichment. Looks like I'll need a TPS.
Old Feb 11, 2008 | 11:30 AM
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Where is your MAP line connected?
If you have it on the nipple by the throttle body you should try Ting it off the FPR line instead.
Old Feb 11, 2008 | 11:36 AM
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Old Feb 11, 2008 | 11:40 AM
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yes
The port near the throttlebody is known to be noisy. It causes issues like you're seeing sometimes. Ting off the FPR port is supposed to cure that.
Old Feb 11, 2008 | 12:30 PM
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Cool, I also had a "no buzz" t piece so I've used that.
Old Feb 12, 2008 | 11:52 AM
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What a difference T'ing in there and using a no buzz T piece has made, look how smooth this MAP is now...
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Old Feb 12, 2008 | 12:07 PM
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Originally Posted by richard_ha
Cool, I also had a "no buzz" t piece so I've used that.
just wondering what is a no buzz?
Old Feb 12, 2008 | 12:13 PM
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Its like a normal t piece but the spout that comes off only has a small hole in it to prevent too much fluctuation.
Old Feb 12, 2008 | 12:58 PM
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You can buy a restrictor for the map line at any advanced autoparts store. AKA No buzz.

Glad that fixed it.
Old Feb 12, 2008 | 07:59 PM
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Originally Posted by bryantaylor
looks like you have your O2 turned on in boost too
Are you sure? Looks like its set to 90kPa to me, unless I'm missing something.
Old Mar 13, 2008 | 05:12 PM
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Originally Posted by cjernigan
You can buy a restrictor for the map line at any advanced autoparts store. AKA No buzz.

Glad that fixed it.
What does this restrictor look like?

Also.. is the vaccuum source next to the throttle body you guys talk about the one on the 1.8 manifold on the top by the fuel rail?
Old Mar 13, 2008 | 05:30 PM
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The restrictor looks like a little plastic tube with a tiny hole in it.
Do not use the one near the throttle body by the fuel rail.
Tee off of the line going to the fuel pressure regulator, it is a much better signal location.
Old Mar 13, 2008 | 05:45 PM
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yeah i was gunna make a thread about my jumpy MAP values. It always fluctuates about 5-10 kpa real fast no matter how steady i hold my foot. Ill try it out and hopefully get a better reading
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