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Old 05-20-2008, 03:50 AM   #21
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are you running a cat? My cat became clogged on screwed up all kinds of stuff. My AFR readings were super lean for some reason and car lost all power around 3500rpms.
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Old 05-20-2008, 06:58 AM   #22
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ok so apprently the white wire coming from olderguy's clamp had become disconnection from the NO terminal on the boost switch.

but since the clamp keeps the car from going lean, doesn't that mean, since it was unplugged, I was going lean? which means I wasn't rich? wtf?

anyways I love my freaking car now. except boost keeps dropping off from a peak of 8-9 to about 5. wtf.

If the wire was disconnected, your ECU was seeing a VERY lean signal (zero voltage)and trying to compensate by adding as much fuel as it could. But it shouldn't have had much effect at WOT
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Old 05-20-2008, 07:02 AM   #23
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ok so I'll revive this thread, and say that I've now installed my aem wideband, and in my fairly dead rpm range (3000-4500) I'm getting 17:1+. After that I'm getting around 13-14 till redline. any ideas? I took apart my vortech and the smaller rubber disc on the bottom was balloned out just a little bit, like it was stretched slightly from the piston?
The bottom disc in a Vortec is thin metal on every one I've seen. The large one on top is rubber and should have the adjustment disc pushing on the piston.
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Old 05-20-2008, 07:45 PM   #24
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the cat is only a couple months old, I'm fairly certain its not clogged.

there's a small rubber disc sandwiched in with the smaller diameter metal disc olderguy's refering to. I'm going to go for a test drive now that I took it apart and put it back together. I also replaced the vacuum line to it, might've had a leak there. the test drive will be very short if I'm still seeing such lean numbers. if the stock fuel pressure regulator isn't working, would it cause this problem?

olderguy, what's a good test I can do with your oxygen sensor to make sure it's working? I'm good with electronics and have a nice voltmeter if its any help
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Old 05-20-2008, 08:27 PM   #25
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Check voltage to ground at the white wire. Should be above .32 and below .47 volts.

Then check to see that the switch is OK with a resistance meter and activate it by blowing into the vacuum line.

What is the boost level when you are getting the 17.1 to 1 AFR?
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Old 05-20-2008, 08:52 PM   #26
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about 5psi. I've boosted around 8 or 9 with the same exact setup, just with a MBC, but that was before the WB, so I don't know what it was doing then.
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Old 05-20-2008, 09:22 PM   #27
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checked voltage, it was .2 volts. is that supposed to be with the engine on or off, warmed up or cold? I started the engine and checked it again, but it was even lower, .15 volts.
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Old 05-21-2008, 01:00 AM   #28
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Engine running. Adjust the voltage up to about .42 volts
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Old 05-21-2008, 10:03 PM   #29
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Ok so I took apart my vortec to see if the diaphragm was torn or anything else was wrong. Nothing. The o-ring had expanded a bunch from the gas and wouldn't go in easily. Thought I had it in correctly, but it leaked real bad, so today once the o-ring had dried and shrunk, I put it all back together, along with a new length of vacuum line, and I'm getting between 10:1 and 11:1 AFR's during boost, and the car is running much better.

Few more questions still through.

I adjusted my AFM clock spring for a 14.7:1 AFR at idle, but the engine was cold. When its warmed up its more like 17:1. I'm really paranoid that when I adjust it when the engine's warm, it'll throw everything else outta wack. Is this a legit concern, or will it not really be effected at WOT?

I still have to adjust the o2 clamp. Does it matter if I do this with the engine cold or warm? It idles a little low and hence rough when its cold, so I'll go ahead and do it when its warmed up, but I wanted to double check.

At first I drove around today with the MBC disconnected, and got a fairly solid 5psi (thanks to a new actuator). Hooked the MBC back up and got a spike of 6-7psi, but it kept falling back to 5psi within a second or two (note this is time dependent, not rpm or throttle position). I wasn't too disappointed in a 1-2psi drop, but when I turned up the MBC to get 8 or 9psi, it was still falling to 5psi, instead of the desired 7-8psi. Seems like once the MBC opens up, no matter what its set at, I'm going to whatever the waste gate actuator is set at. at this rate I'm going to space back the actuator for higher boost and just use the MBC for better spool. Anyone else experience this with their MBC? Its FM style, including the little hole to bleed off some of the pressure.
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