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Old 07-02-2011, 05:03 PM   #1
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Default What can cause me to be leaning out?

The car is tuned on an AEM F/IC piggyback with 305cc Supra green top injectors. Running about 10psi on my GT2554R. A few weeks ago the car ran like crap and would misfire. Today I finished putting on the test pipe, getting a recirculating blow off valve on, and fixing the leaving idle air control valve. I thought this might solve my problems (high hopes), but nope. The car run smoother now, but still lean.

I bought the car boosted and it would always have a steady 10.5-11 AFR in boost at WOT, but now it fluctuates around 12-15... obviously a bad thing. So what could cause this?

-Fuel pump?
-BEGI FMU?
-Poorly gapped plugs?
-Bad coilpack?
-Bad O2 sensor?
-Bad crank angle sensor?
-Bad crank position sensor?
-Bad injectors?
-Tune gone bad?

The car sometimes doesn't even turn over, I noticed this seems to happen after I fill up (maybe a coincidence). But if I let it sit for a minute or two, it'll start right up. It still randomly will run on what seems like 3 cylinders, but will correct itself. It's still good enough to daily drive, but I'm not sure what to do. I need to rule things out and check things that could be the culprit. I want to throw in some 550cc and MS, but not unless I can find someone to tune it or be sure it'll fix my problem.
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Old 07-02-2011, 06:53 PM   #2
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Quote:
Originally Posted by _spyder View Post
So what could cause this?

-Fuel pump? Yes
-BEGI FMU? Yes
-Poorly gapped plugs? Yes
-Bad coilpack? Yes
-Bad O2 sensor? Symptom
-Bad crank angle sensor? No
-Bad crank position sensor? Unlikely
-Bad injectors? Yes
-Tune gone bad? Maybe
Plug Wires.
Loose nut behind the steering wheel.
Band-Aids.
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Old 07-02-2011, 07:52 PM   #3
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Do you have an AFPR or FMU? Might want to get one
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Old 07-03-2011, 03:42 AM   #4
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Quote:
Originally Posted by fooger03 View Post
Plug Wires.
Loose nut behind the steering wheel.
Band-Aids.
Tried new wires, nothing.

Quote:
Originally Posted by spitefulcheerio View Post
Do you have an AFPR or FMU? Might want to get one
Yes, BEGI AFPR... or FMU, not exactly sure what the difference is.
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Old 07-03-2011, 01:13 PM   #5
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What you need to do is start tuning your F/ic. It sounds like you have a wideband, so I would start by enriching the areas that are running lean when in boost. It's very simple with the f/ic to do.
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Old 07-03-2011, 03:58 PM   #6
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I honestly have no idea what I'm doing, never tuned or watch someone tune a car. I know the injectors are pretty maxed out for their size and my boost. If I could find someone local just to look at the tune or help me figure it out I bet that'd save a lot of time. But a tune shouldn't just go bad over time should it?
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Old 07-03-2011, 04:20 PM   #7
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Originally Posted by _spyder View Post
I honestly have no idea what I'm doing, never tuned or watch someone tune a car. I know the injectors are pretty maxed out for their size and my boost. If I could find someone local just to look at the tune or help me figure it out I bet that'd save a lot of time. But a tune shouldn't just go bad over time should it?
It's just like an excel spreadsheet. The f/ic shows you what cell you are in. If you go lean at that cell, then you increase the amount of fuel. It really can't get any simpler.
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Old 07-05-2011, 05:22 PM   #8
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I'll have to download the program (if I can find the correct one?), and fire her up and see what I can do.
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Old 07-05-2011, 06:15 PM   #9
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Well if you used to not run lean and you have not changed the tune then i would continue to search for what caused the problem. Start with a compression check, a/f ratios in the 15s will burn things up faster then you could imagine. If all comes back well with compression then you move on to the fuel filter, if it hasn't been changed in a while then i couldn't hurt and im pretty sure they are cheap. Next do a fuel pressure test, everything to do this can be had from Napa for around 50 bucks and it will really come in handy. If the pressure checks out good then i would turn to the parts which i would guess to be the culprit, fuel injectors, have them tested. If none of those things are a problem then you are probably not running lean do to a fuel delivery problem, but due to more air comming in.
Like i said, its prolly the injectors.
I was under the impression that the stock 1.8 ecu could handle supra 305s maybe you could rule out the fic by running it on stock ecu.(not sure about this so if you try it keep a close eye on that wideband)

Last edited by 1slowna; 07-05-2011 at 07:37 PM.
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Old 07-12-2011, 04:09 AM   #10
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Issue has been solved. Turns out the vacuum line running to the F/IC was pinched, therefore the F/IC wasn't getting a vacuum signal to do it's thing. Fixed it and the car is back to running great. It's even better with the recirculated BOV too, I'm pumped!
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