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914World.com _ 914World Garage _ How do you check your ECU knob setting?
Posted by: ThinAir Jul 21 2020, 10:20 PM
Years ago at a Route 66 Classsic, Joe Sharp had a device that he connected to the tailpipe and could quickly tell if the mixture was correct and adjust the ECU knob as needed. My car ran fine for years until I messed up and failed to document the position before moving the knob while working on another issue.
I have a Gaston CO gauge (http://www.gunson.co.uk/product/G4125 ) that I thought would allow me to set this, but I've used it on both my D-Jet 914 and the L-Jet in my sons bus without good results. It seems no matter how I adjust things, the CO never settles down or gets down to an acceptable level so that I can be certain that I have things set right.
What do you all use so that you can be sure you have the ECU set right?
Posted by: nordfisch Jul 22 2020, 04:42 PM
Years ago at a Route 66 Classsic, Joe Sharp had a device that he connected to the tailpipe and could quickly tell if the mixture was correct and adjust the ECU knob as needed. My car ran fine for years until I messed up and failed to document the position before moving the knob while working on another issue.
I have a Gaston CO gauge (http://www.gunson.co.uk/product/G4125 ) that I thought would allow me to set this, but I've used it on both my D-Jet 914 and the L-Jet in my sons bus without good results. It seems no matter how I adjust things, the CO never settles down or gets down to an acceptable level so that I can be certain that I have things set right.
What do you all use so that you can be sure you have the ECU set right?
Hi,
the ECU-knob only effects the mixture at idle - when idle-switch of the TPS is closed. It doesn't effect the 'normal' engine mixture.
When your engine is running rich, the most common reasons are:
- MPS diaphragm broken, MPS doesn't hold the vacuum <D-Jetronic only>
- temperature sensor wire broken or sensor defective
- vacuum leaks.
This would effect the mixture at idle, too.
Regards
Norbert
Posted by: 76-914 Jul 22 2020, 07:50 PM
IIRC, there are 11 detents either side of the middle position. With the idle set at 900 and the knob centered turn 1 click at a time and give the engine 20 seconds or so between clicks so it has time to react and adjust to the newest setting. I think clockwise was rich and CC was lean but you'll discover which is which. May require small adjustments to the air jet on the throttle body as you tune it in. One effects the other to some extent. The lower the rpm the easier it is to detect changes in the idle. 
Posted by: ThinAir Jul 22 2020, 11:32 PM
Years ago at a Route 66 Classsic, Joe Sharp had a device that he connected to the tailpipe and could quickly tell if the mixture was correct and adjust the ECU knob as needed. My car ran fine for years until I messed up and failed to document the position before moving the knob while working on another issue.
I have a Gaston CO gauge (http://www.gunson.co.uk/product/G4125 ) that I thought would allow me to set this, but I've used it on both my D-Jet 914 and the L-Jet in my sons bus without good results. It seems no matter how I adjust things, the CO never settles down or gets down to an acceptable level so that I can be certain that I have things set right.
What do you all use so that you can be sure you have the ECU set right?
Hi,
the ECU-knob only effects the mixture at idle - when idle-switch of the TPS is closed. It doesn't effect the 'normal' engine mixture.
Yep, idle mixture is all I am trying to set.
Posted by: yellowporky Jul 23 2020, 08:58 AM
Yes clockwise is rich. There is a bump at 9 oclock on the ecu and i was told that that was the factory setting but it was too rich so i backed up on notch counter clockwise
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