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Very high negative fuel trim at idle

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Very high negative fuel trim at idle

 
Old 03-13-2019, 05:24 PM
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https://www.s2ki.com/forums/s2000-un...lenoid-539908/
Someone else with the same issue on this forum. I didn't get around to checking my solenoid valve. I'l definitely do it tomorrow. This seems to be the winning number.
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Old 03-13-2019, 05:25 PM
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Thanks Billman. I just learned all that in the last couple hours of reading lol. People are blocking off the holes in the head and what not when going FI.
Apparently at idle the evap purge solenoid should not be open. If it were it would explain the extra fuel my car is getting from the evap canister and also why it runs fine while cruising. I loosened the gas cap today to see if I released the pressure from the tank if it would have an effect. I heard a bit of vapor rush out of the cap. I started my car and it appeared at 1st to have worked. Fuel trims at idle were lower than ever. I drove around another 15 minutes and when I stopped the fuel trims went back negative. It wasn't as bad as before though. Hovering between -8 and -12 and peaking at -14 coming to a stop.
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Old 03-13-2019, 05:50 PM
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Originally Posted by flanders View Post
Just another suggestion, probably not likely but there is also another fuel source that might affect things.
The fuel purge valve should only open above 149F coolant temp, it purges fuel vapor from the EVAP canister to the intake manifold.
This would explain why when I started my car cold in the morning there wasn't excess fuel being dumped into the exhaust assuming all the pressure in the tank has bled off. That would be the 2nd video I posted. In the 1st video I posted I had driven the car maybe 2 hours prior and more than likely had pressure in the gas tank thereby dumping excess fuel in the intake causing gurgling, popping, and back firing. Assuming this valve were stuck open 24/7., According to the post I link above, it's very possible to not throw a code if certain criteria aren't met and still have this problem and also why it's intermittent and moreover happens more often in the summer when it's hot.
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Old 03-14-2019, 08:28 AM
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Quick question. I pulled the middle vacuum hose off the intake that routes to this purge solenoid valve. I could blow and suck it. Tasted like fuel. I'm assuming the valve should only be open under power. Can blowing on it from this end diagnose my issue?
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Old 03-14-2019, 08:32 AM
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Just realized it was T'ed to another port. I blocked it off and air wouldn't pass through.
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Old 03-14-2019, 08:37 AM
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Originally Posted by kikkomon View Post
I could blow and suck it. Tasted like fuel.
Don't do that
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Old 03-14-2019, 08:37 AM
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http://www.atraonline.com/gears/2007...2007_08_08.pdf
If voltage from the O2 heater circuit bleeds into the signal wire, it will register a high voltage at the PCM. The PCM will falsely recognize this as a rich condition.

How do I test this circuit?

Seriously FML
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Old 03-14-2019, 02:43 PM
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Not sure what happened but today I had zero hesitation. Fuel trims at idle pushing more towards normal. Hovering between -7 and -10 at idle dipping to -5 at idle occasionally. It was warm today too and other than the typical minor loss in power down low due to intake temps the thing ran perfect all day. I decided to finally open her up. Hit 8500 rpm for the 1st time since the rebuild. She pulls pretty hard. Makes me wanna bust too fast. Ran an STI on the highway today. He appeared stock. We appeared to be evenly matched. Hit 96 MPH and I let off while he kept going. I circled my highways and stopped at a bunch of lights watching my trims and everything seems to be ok. To anyone eyeballing the Nvidia Q300. I highly recommend it. It sounds amaZAHzing. It does have drone between 3-3500k rpm but its not bad at all compared to the N1. With the top down there's hardly any drone at all anywhere. But I guess this is for another post.
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Old 03-14-2019, 10:38 PM
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Originally Posted by kikkomon View Post
Not sure what happened but today I had zero hesitation. Fuel trims at idle pushing more towards normal. Hovering between -7 and -10 at idle dipping to -5 at idle occasionally. It was warm today too and other than the typical minor loss in power down low due to intake temps the thing ran perfect all day. I decided to finally open her up. Hit 8500 rpm for the 1st time since the rebuild. She pulls pretty hard. Makes me wanna bust too fast. Ran an STI on the highway today. He appeared stock. We appeared to be evenly matched. Hit 96 MPH and I let off while he kept going. I circled my highways and stopped at a bunch of lights watching my trims and everything seems to be ok. To anyone eyeballing the Nvidia Q300. I highly recommend it. It sounds amaZAHzing. It does have drone between 3-3500k rpm but its not bad at all compared to the N1. With the top down there's hardly any drone at all anywhere. But I guess this is for another post.
This is quite weird to say the least man... I have never had these issues so I'm sorry that I can't help you from a direct experience POV. That being said, you mentioned the vacuum hose on your EVAP purge valve having a hole or something? Or was it another hose...?

About the exhaust - its Invidia and not Nvidia like the graphics cards
It's a good exhaust and one of the most popular. Love/hate thing in our community though. I think it sounds really good. I have a J's Racing FX70RS titanium single exit on my '00 AP1 and that absolutely slays!! Amazing tone/character. Love it all the way from 1000rpm to 9200rpm It saves a significant amount of weight too Makes me wanna bust too fast too
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Old 03-16-2019, 02:39 PM
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Yeah this "IN"vidia exhaust sounds nice and mellow when you're cruising which is what I wanted. At 3500 rpm with top up, if you dip in to the throttle a bit it drones but is easily remedied by just letting off a bit. At 4k rpm ~70 MPH there's almost no drone at all no matter what you do on the pedal. Didn't mention my car has a Berk HFC. But Jesus, right around 5k and up it sounds absolutely fantastic. Loud as all get out too. Then you see a cop and it's a stock exhaust again. ;-)
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