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LS1 tach and almost stall problem

Old 02-14-2019, 07:02 PM
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Default LS1 tach and almost stall problem

Evening all,

I have a LS1T56 combo in my 68 C10.
I had the engine/trans in a 1999 E36 BMW and had it chassis dyno tuned. Ran well 380 rwhp. It runs well. No bucking or surging.
Engine specs:
2002 LS1. AFR heads. 216I/220E with .532 lift. 114 C/L 10.5 compression. LS6 intake. Stock LS6 injectors so 28.8 lb?
First problem. The tach reads about 800 rpm high at idle. I have a scanner and at idle the scanner reads about 800 rpm. I'm running a Autometer speedo and have the dip switches set to the 4 cylinder positions. Can settings be changed in the ECM so the tach reads correctly? I've used Autometer tachs before and they were spot on rpm wise. Tach read high in the stock BMW also.
Second problem. Almost stalling if I let up quickly on the gas as I come to a stop. Doesn't do it all the time. I opened the throttle blade slightly which helped. Replaced the IAC solenoid. No difference. I do not have a VSS signal to the ECM. Harness does not have the wiring. I've read it's best to have a VSS signal to the ecm but with such a mild combo can it tuned to prevent the stalling?
I'm wondering if a mail order tune could correct these problems? I'm about 150 miles from the nearest chassis dyno and I'd just like to just pull the ecm and send it out for tuning before the weather gets nice here in MN rather than drive to the MPLS area.
What does everyone think?
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Old 02-14-2019, 07:17 PM
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The tach output signal in the pcm needs to be changed. I would not recommend a mail order tune to correct the issues your having especially since you dont a VSS signal.

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Old 02-14-2019, 08:10 PM
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Thanks for the input.
Yeah I was thinking the tach signal is an easy fix. Not so much on the stalling. The irritating part is it does maybe 10% of the time. Other wise it runs great.
Thanks again.
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