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High Idle/Strange A/F readings

 
Old 03-02-2007, 09:56 AM
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Default High Idle/Strange A/F readings

Hi Guys,
This is my first post so try not to beat me to bad . I've got a 93 with the basic Greddy install. I have also installed a Bipes controller, VTA BOV, Faze A/F gauge, and Faze Boost Gauge. My timing is set at 13 deg and I am running 'WhiteRoadsters' Basic Bipes settings. My problem is I can't get the RPM's at idle down past 1200. It used to run 1000 rpms before I was working on the Cruise control. The cruise control had a major problem due to the fact it stuck wide open and started racing me down the interstate 95+ . I resolved that issue by replacing the cruise cable. It had got too close to the turbo and melted the cover off. The new cable received heat tape so I won't have that issue again. I have checked for a vacuum leak by spraying everything with Carb cleaner and can't find one. I also do have all new silicone vacuum lines on it. I did check the A/F screw on the throttle and it is a quarter turn loose from completely tight. Second, The a/f gauge shows that I'm running a little rich at idle but as soon as I touch the gas driving it will either jump between just rich or bottom end lean, or just drop off the gauge lean and not show any condition. Any Ideas?
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Old 03-02-2007, 11:05 AM
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Vent-to-atmosphere bypass valve.
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Old 03-02-2007, 11:55 AM
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Originally Posted by Brian View Post
Vent-to-atmosphere bypass valve.
+1

Running VTA on an AFM-equipped vehicle is always suspect unless certain precautions are taken. Many valves are slightly open at idle, and thus leak. As a result, you've got unmetered air going into the engine, though this would generally cause the engine to run lean. (Before I removed my AFM, running my FM BOV with no checkvalve would actually stall the engine at idle.)

What kind of BOV do you have?

Also, I hate to be a downer but that A/F gauge you've got is not going to be very useful for tuning a turbo'ed engine. Gauges that use the stock narrowband sensor are only accurate within a narrow range centered around stoich- they can't tell the difference between 10:1 (bad) and 12.5:1 (good). To the narrowband gauge, they're both just "rich."
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Old 03-02-2007, 12:44 PM
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+1 I added a "check valve" to my VTA dsm "bov" and it stopped the idle weirdness and runs better...
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Old 03-03-2007, 06:31 AM
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I don't know who makes the bov. It came on the car and knowing the PO it probably isn't the best of quality. I'm going to the junkyard and pickup a recirculating valve off of a saab I found. I wish I had the cash and I would pickup its intercooler at the same time. Thanks. Oh one more question when I plumb the valve do I attach it back just beyond the AFM? Thanks
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Old 03-03-2007, 09:57 AM
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You want to attach it so the face of the valve and the spring on its backside are pointed directly at/perpindicular to the charge pipe, while the other side, the vent, would attaches somewhere post-AFM but pre-compressor inlet.
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Old 03-03-2007, 06:04 PM
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