TB Bump Stop Fine Tune
TB Bump Stop Fine Tune After grinding the bump stop to get the WOT TPS DC voltage up to 4.6 VDC I also tried to LOWER my closed throttle DC voltage to try and get it closer to ZERO VDC. BAD IDEA! It wouldn't idle properly after I got the sense wire (BLUE) close to 0.2 VDC. I decided to get the GM shop manual out which I should have done in the first place. The TPS DTC P0123 (HIGH VOLTAGE) goes SET at 4.75 VDC so any value of 4.74 VDC or less is OK for the throttle bump stop mod. The TPS DTC P0122 (LOW VOLTAGE) goes SET at any value < 0.2 VDC so you would think that something in the range of 0.2 VDC to 0.5 VDC would be OK. Wrong! That's the range where you get the erratic idle speeds. The manual says it "should be near 0.6 VDC at idle". You can't use an analog meter to get the kind of accuracy you need to adjust your TPS. You need a good quality DIGITAL VOM like my FLUKE Model 12B to do this adjustment. It measures voltages down to the 1/1,000th of a volt. You only need that kind of accuracy when your working on heart pacemakers, but it doesn't hurt when your adjusting the output of the TPS on your LS1. The manual says NEAR 0.6 VDC so I set mine at 0.595 VDC. I guess you could go slightly over 0.6 VDC because the manual doesn't say which side of NEAR you need to be on.
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Joined: Nov 2001
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From: TEXAS
Re: TB Bump Stop Fine Tune Well, mine varies from .500 to .600 closed. It seems like its slightly different whenever the throttle blade closes again, but its always within that range. It could just be my contacts on the wire.
