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Discussion Starter #1
Hey folks, looking for some help. Just got done with a PD2 class at Sonoma Raceway today and hit limp mode/SES light during the last 2 runs of the days.

Codes:
90 - Misfire Cyl 1-4
95 - Misfire Empty Tank
C4 - Misfire Cyl 1
C6 - Misfire Cyl 3
CC - Misfire Multiple Cyl

It drove great during the first part of the day, no codes no issues. Only happened on the back half of the day. I searched the older threads and it seems to be centered around Coils/MAFs/TPS but nothing concrete for a fix.

Another thing to note is that I filled up after the track day and my fuel centered at half tank and then slowly crept up to 2/3rd full but I know for sure the tank was full.

I’ve replaced the following items in the last 10K:
Fuel Filter
Spark Plugs

Car has 156K on it currently. Driving home approx 40 miles, ZERO issues. No codes, no limp mode, no stuttering.
 

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95 - Misfire Empty Tank
That is the code you have to figure out, the others are just icing on the cake and come because of the 95. It is not easy to figure out but it is not to hard to figure out once you know what it means. Misfire on empty tank is just a weak translation, really what is trying to be said is misfires with very lean condition at the O2 sensor. Often this points to bad MAFs or weak fuel pump, but it could also be old O2 sensors, half bent fuel line, you name it and if it has to do with fuel delivery it could be a fault. If you can look at your fuel trims that might tell you something.
Normal first test would be to unplug the MAFs but since you say it only happens at the track that might be risky. The air temp sensor is in the MAF and it might not be too wise to push the car hard with no IAT. Now it might not be too risky to wait until it happens then unplug the MAFs for one lap and see if the problem stays or goes.
In any event you have some thinking and reading there are tons of threads on diagnosing mixture issues so start there.
 

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Discussion Starter #3
Thanks for the reply Sailor. I was trying to recreate the scenario in my head and I’m pretty sure the codes popped up after I was at half a tank and going up 2 uphill turns. I’m gonna run the console test I found earlier to see if the tank is sending any errors. I feel like the fuel issues coupled with the gauge not reading correctly its a good place to start. I believe the fuel pump and sender are both originals from 2003.
 

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Check the secret menu for codes. You're looking for D7 (driver side sender) and / or C7 (pax)

Uphill T2 there if you're lower on fuel than you think is going to cause starvation. Since everything is on the pax side and you're leaning left away from the pump... I'd start there...

PFA

 

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My guess is fuel pump and/or siphon pump.

You would be amazed how hot the fuel pump and fuel can get in the tank. The fuel helps cool the pump. As you burn down the tank, there's less to help keep the pump cool. If it's on the way out already, it may have started to run slow and not put out the appropriate pressure. Another theory is with the siphon pump not working to keep the right tank full of enough fuel which will also cause starvation and the symptoms you encountered.
 

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Discussion Starter #6
Checked the codes when I got home and it’s a D7. So you were right @mgdmb The question now is I assume I should replace both the pump and sender while I’m in there? I’m pretty sure both parts are original from ‘03.
 

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Checked the codes when I got home and it’s a D7. So you were right @mgdmb The question now is I assume I should replace both the pump and sender while I’m in there? I’m pretty sure both parts are original from ‘03.
If I were you I'd replace both of them at the same time to save yourself from a future annoyance.
 

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Checked the codes when I got home and it’s a D7. So you were right @mgdmb The question now is I assume I should replace both the pump and sender while I’m in there? I’m pretty sure both parts are original from ‘03.
D7 is driver side

If you don't know the age of the fuel pump though, I'd at least consider a swap
 

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You might have two issues going on. Your codes are all on bank 1. Code 90 is not misfire bank 1, it's "fuel control" meaning a fuel trim problem. You need to check your fuel trims to see if it's lean or rich. I would suspect a vacuum or exhaust leak on bank 1.
 

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Discussion Starter #10
Sounds good. I ordered the fuel tank parts, is it safe to replace them and then test for the leak? Or is there an easy way to test while I wait for the parts?
 

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Easiest would be if your code reader can look at fuel trims. If not, using INPA or ISTA to read them.
 
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