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Old 03-19-2014, 09:55 PM   #1
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Default Need help with my 2001 Miata

I have a 2001 Miata that has roughly 75k miles on it. There are a couple of issues that have me baffled and I would appreciate any input.

Setup: Stage 3 Garret Turbo, olderguy o2 clamp, BEGi FPR with inline fuel pump, K&N cone filter, intercooler, and an aluminum radiator. The rest of the car appears to be stock for the most part, although most of this work was done by the previous owner, so I might be missing something.

The car has been running rich, even at idle. I continuously get error code p0172. I've changed both the o2 sensor and MAF within the last 5k miles, so they should both be good. I checked fuel pressure, and it's always between 55-60 psi while the car is at idle. After letting the car sit for 5 mins, the fuel pressure is still 55-60 psi, so I doubt that the fuel injectors are leaking.

I believe the following issue ties in to the prior. The car doesn't seem peppy at all. Under WOT acceleration, the car slowly gains boost, but it seems off and sluggish. When I disconnect the battery for a few minutes, the car seems completely different, being extremely responsive and acting like a turbocharged car. Now of course this changes over a couple of drive cycles, and long term fuel trim slowly settles to about -20.3%. I'm assuming that the high negative fuel trim is modifying open loop operation.

Now some other issues that may or may not be related to the prior issues. The car has been consuming oil, although I recently changed the valve cover and that seems to have helped. The car has issues starting after sitting. It will start up for a second, and then stall out. If I try starting it again, it starts up just fine. The car also has issues with idling. I basically have to stay in gear until I stop; otherwise I run the risk of stalling out. According to my boost guage, the car idles at roughly 16-17 psi of vaccum, which seems a little high, but is rock steady. I also recently got error code p0133 under pending codes.

I've done a lot of the basics, including changing the oil with synthetic, new plugs, new wires, and Iíve cleaned the air filter. Any input would be greatly appreciated, as I'm at a loss.
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Old 03-20-2014, 09:41 AM   #2
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Sounds like you need to adjust something so that your idle fuel pressure is down to around 36ish psi (aka ~44psi with the vac line unplugged from the fpr). Then fiddle with the rest of the afpr crap so that it still has a safe arf in boost.

Or just scrap the AIDS and put in a standalone.
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Old 03-20-2014, 07:49 PM   #3
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If I'm not mistaken, this is a returnless system, so I shouldn't be able to adjust the fuel pressure.
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