Erratic RPM readings on 4l80e - Team Camaro Tech
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post #1 of 2 (permalink) Old Apr 13th, 10, 06:54 AM Thread Starter
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Location: Nashville, TN
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Erratic RPM readings on 4l80e

I'm using an Acell Coil part number 8140c.

My regular tach reads fine but when I connect my PC to monitor my electronic transmission thru its' computer jack the trans RPMs readings are erratic. shows 0 to 20k rpm. It's been suggested the problem is the Acell coil.

Has anyone run into a similar RPM metering problem?
Could switching a different coil such as the MSD Blaster 2 Coil 8202 (the secondary resistance is different then the 8140) be a solution to this problem?

Steve - (fixdaserver)
'69 Restomod.
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post #2 of 2 (permalink) Old Apr 14th, 10, 06:43 PM
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Join Date: Mar 2002
Location: Austin, TX, USA
Posts: 5,277
Re: Erratic RPM readings on 4l80e

It's possible the ECM gives your diag tool priority and the instruments have to sleep between data packets. Modern day instruments are often driven by the ECM. If the ECM's busy, it may presume you can live without knowing RPMs accuratly.

Did it not do it with the old coil?

68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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