AFM problem ?
11-09-2014, 12:01 PM
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Racer
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AFM problem ?
1984 N/A, stock engine, catless with Flowmaster muffler: DE car
I'm running into a weird and hard to duplicate problem. Earlier this year I upgraded to the '86 DME & AFM and added a 4^ advance cam key. Engine feels great and I like the smoother idle and improved lower end torque.
I tested the AFM prior to installing using the Clarks garage and The944.com procedures. Bench performance was spotless.
In August on the way to a DE I noticed that during long highway driving at steady throttle the engine would occasionally bog and the AFR would go into the 17 to 18:1 range. WOT throttle would clear this up instantly and it would last for anywhere from 20 minutes to several hours. I cleaned the AFM connector and had no more trouble during the DE, nor the ride home.
This Friday I had another DE. I had the bog & AFR problem one time during the 3 hour trip there. I cleaned the AFM connector again but it was spotless anyway. During my first two sessions the car seemed okay but lap times were 2-3 seconds off. Then I started to pay attention the AFR. At idle the AFR would slowly work its way from 14.6 to 17.1. Snap the throttle and the process would repeat. On track WOT AFR readings varied from 13.1 to 10.8. This was worst on the last session if the day. The power was flat and the car slow.
During the 3 hour trip home the bog came a couple of times but the car is very drivable and reliable otherwise.
Before I spend hours chasing gremlins, have any of you experienced these symptoms?
I'm running into a weird and hard to duplicate problem. Earlier this year I upgraded to the '86 DME & AFM and added a 4^ advance cam key. Engine feels great and I like the smoother idle and improved lower end torque.
I tested the AFM prior to installing using the Clarks garage and The944.com procedures. Bench performance was spotless.
In August on the way to a DE I noticed that during long highway driving at steady throttle the engine would occasionally bog and the AFR would go into the 17 to 18:1 range. WOT throttle would clear this up instantly and it would last for anywhere from 20 minutes to several hours. I cleaned the AFM connector and had no more trouble during the DE, nor the ride home.
This Friday I had another DE. I had the bog & AFR problem one time during the 3 hour trip there. I cleaned the AFM connector again but it was spotless anyway. During my first two sessions the car seemed okay but lap times were 2-3 seconds off. Then I started to pay attention the AFR. At idle the AFR would slowly work its way from 14.6 to 17.1. Snap the throttle and the process would repeat. On track WOT AFR readings varied from 13.1 to 10.8. This was worst on the last session if the day. The power was flat and the car slow.
During the 3 hour trip home the bog came a couple of times but the car is very drivable and reliable otherwise.
Before I spend hours chasing gremlins, have any of you experienced these symptoms?
11-09-2014, 02:16 PM
#2
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Join Date: Aug 2011
Location: Urbana ,MD
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I have experienced similar symptoms. When the car was warming up I would get the same bog that would last 10-20 minutes and flooring it would fix it a bit. I moved the AFM arm and it barely helped, then I replaced the o2 sensor and for some reason that fixed it.