Air/Fuel mix experts needed. Options

[malcolm2]

Hey hey... I need some suggestions. I went for a nice drive last nite. I have a AFR gauge that has not been working. But the PLX Devices system has a blue tooth transmitter so i can review the live data on my phone.

I was getting 10.5 A/F reading. It did jump to 12.5 as i went to neutral and coasted to a stop.

To start with, I was thinking i would pull the sensor and take a look, maybe clean it up and re-drive.

Any ideas about the 1st steps? The car seemed to run fine.

I will need to look them up here, but years ago I had a reply from, I believe, Mark Henry that gave me the following:

13.5-12.9 while accelerating of climbing
12-8-12.5 at WOT
16-17 going downhill or decelerating.

1911 cc L-Jet. I did tweek the AFM back in the day. 62,000 miles ago.

the link to the 5 page post from 2017

[malcolm2]

intenerant air cooled community SPRING ADJUSTMENT

I used that link some 10 or 15 years ago. Guess I will read thru it again. That spring could POP at any second during my operation.... IIRC I had to adjust, then adjust once more. So i did it twice. It was very scary. (IMG:style_emoticons/default/piratenanner.gif)

So that being said, this car has run with that spring setting for more than 10 years.

What would all of a sudden make it so rich?

After i check the AFR set-up, I might go to the 5th injector. Maybe it is stuck.

Any other thoughts, let me know. I have a few days of home time before the kids fall break.

Clark
615-504-1086

[emerygt350]

intenerant air cooled community SPRING ADJUSTMENT

I used that link some 10 or 15 years ago. Guess I will read thru it again. That spring could POP at any second during my operation.... IIRC I had to adjust, then adjust once more. So i did it twice. It was very scary. (IMG:style_emoticons/default/piratenanner.gif)

So that being said, this car has run with that spring setting for more than 10 years.

What would all of a sudden make it so rich?

After i check the AFR set-up, I might go to the 5th injector. Maybe it is stuck.

Any other thoughts, let me know. I have a few days of home time before the kids fall break.

Clark
615-504-1086

I am not an ljet guy but there must be a temp sensor or two in the system, not just the flapper. If one of those goes, or the ground/wiring is funky, it might send it rich. That is the first place I look on fuel injection cars.

[JamesM]

So that being said, this car has run with that spring setting for more than 10 years.

What would all of a sudden make it so rich?

I am not an ljet guy but there must be a temp sensor or two in the system, not just the flapper. If one of those goes, or the ground/wiring is funky, it might send it rich. That is the first place I look on fuel injection cars.

The the "joy" of analog injection systems, especially 50 year old ones, is that anything that impacts the resistance of several key circuits impacts your mixture, and you may not even be looking at a single source.

So:
Oxidized connectors
loose connectors
broken wiring
corroded wiring
shorted wiring
bad ground paths
worn AFM traces
Weakening AFM flap springs
Partial failure of anything in the ECU itself
EMI from bad ignition components

Because you have no centralized visibility of the system the only way to diagnose is to individually test every component and circuit through the harness itself.

It is not a small task.

I used to be a purist when it came to retaining stock injection systems however as someone that owns 914s specifically to drive them the cost(in dollars, time, and reliability) vs benefit has shifted to favoring replacing with modern electronics.