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Old 01-20-2008, 10:07 PM   #1
wittmer25
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Join Date: Dec 2005
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Location: Waco, TX
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2004 STi gt30r
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Default Engine won't idle after engine install

I just finished installing my new engine. I have a gruppe-s built shortblock, diy ported heads, cosworth cams, perrin gt30r kit w/ perrin el header, modded injectors, walbro fuel pump, tvg deletes, and alot of other crap. I tune w/ enginuity and have a datalog if anyone is interested in looking at it. I programmed all of the idle maps with 2000 rpm for cam break-in.

The symptoms are that it seems to be starving for fuel. With engine running, it trys to idle but lower than 2000 rpm. I have correct fuel pressure. I noticed that the front oxygen sensor does not change from 14.7 afr even when the engine is not running w/ the key on. The resistance and current do not change which is strange when the car is running. 0.00 amps & like 255 ohms. There is also zero change in the fuel trims which is also very strange.

Before the built block and heads, I had stock heads and block along with the walbro fuel pump, modded injectors, and perrin gt30r kit w/ header. It ran fine with my personal tune.

I did not change any timing maps or fuel maps (i didn't think it was needed to get the motor started and cams broken in), only the idle map values. I don't have any check engine lights either. I was thinking maybe a intake manifold vacuum leak, but my boost gauge shows plenty of vacuum and I still think it has something to do with the oxygen sensor.

Any insight would be much appreciated.

Jonathon
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Old 01-21-2008, 10:51 AM   #2
wittmer25
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Bump for help on no fuel correction. What controls fuel correction other than input from the oxygen sensor and engine load/speed? The afr should be around 21 when the engine is not running but the key is in the on position. Why would it stay at 14.7?
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Old 01-21-2008, 11:10 AM   #3
gabedude
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Your front O2 is broken, unplugged or something. It should never read only 14.7. This is why your car is behaving like it is. Log AFC #1 and AFL #1. If AFC #1 is 0, then it is the O2 (this thing should bounce all over the place rapidly all the time when in closed loop).

Gabe
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Old 01-21-2008, 12:40 PM   #4
wittmer25
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Thats what I thought. It says the same thing when its unplugged. Guess I will be getting a new 02 sensor.
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Old 01-21-2008, 02:14 PM   #5
wittmer25
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I had another thought. Doesn't the ecu disregard the front O2 sensor during cold start up? Maybe I need to adjust the warm up fuel enrichment map due to the cosworth cams (high lift & duration)?
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Old 01-21-2008, 11:57 PM   #6
wittmer25
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nevermind... I got it fixed. I had originally had my MAF housing located farther away from the turbo. During my engine install I relocated it closer to the turbo but did not change my mafV vs airflow map.... and I had a vacuum line loose. opps, I know... classic rough idle, engine starving for fuel symptoms due to loose vacuum leak. Anyway, its all good now... the cams sound bad a$$!
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