Quote:
Originally Posted by porschyard
Kinda hard to diagnose over the phone as there can be a multitude of things that can cause this but here are some checks and info. With KOEO disconnect fuel pump safety connector on the back of the air flow meter and make sure the frequency valve is running (audible test). Passing that start car and do a duty cycle % test at the test plug on the relay plate, looks like a round relay plug connector. I don't have the pin diagram or the spec off the top of my head but should be easy enough to find. I want to say at idle the duty cycle should be in the 55% range.
Have you tried disconnecting the O2 sensor, if so what happens. Have you looked at the timing, does not sound like thats the issue but you need to start with basics of timing and fuel mixture.
On the 86-89 USA 911 turbos the lambda system runs closed loop up to 3000 rpm or a 65 degree throttle angle, once you pass either of those threshholds it goes in to open loop so if the engine runs ok past 3000 rpm it sounds like something is leaning it out during closed loop (O2 sensor ?)
Again kinda hard to diagnose without being there or lots more info. Hope this little bit helps.
Richard
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Quote:
Originally Posted by Rawknees'Turbo
^^^
One thing that can cause the fuel pumps to run with the key on is a bad contact with the pins of the yellow relay (people call it the overboost relay, but it really isn't - I think the parts manual refers to it as the air metering relay). Mine was doing that and I could get the pumps to shut off by wiggling that relay in its socket. I first tried cleaning the pins and socket, but that didn't work, so took the cover off the relay and saw that two of the pins had cracked solder around them, so I reflowed the solder with a small-tipped iron and all good.
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Quote:
Originally Posted by RarlyL8
Unplug Lambda and manually set idle mixture to ~13.0:1 AFR then see what happens. Most likely culprit. Next would be the air meter assembly. This change happened abruptly which is indicative of these two issues.
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Thank you for the detailed info, I will do some more digging tomorrow and report back. I failed to mention the O2 sensor is, and has been unplugged.