Every time I start the car it will idle @14.7 A/F but then after about 10 seconds the cars sound will get deeper and the wideband will drop to 10.0. It will come back to maybe 11.0 but never above that at idle. When I rev it up the A/F acts normal and stays in a normal range but once it comes back down to idle the A/F drops like a rock back down in the 10.0 range. I can shut off the car and restart it and it will do the same thing.
Vacuum is a constant -18 which is normal for this car. RPMs stay solid and it doesnt speed up or slow down like a bad TPS wire.
Its in the begining tuning stage right now so it could easily be in the tune but since it starts out correct and then goes south it has me wondering.
Any ideas?
Last edited by porksword : 10-19-2009 at 12:36 AM.
Do you have any fuel mods? 1:1 reg or return line?
Yes, returnline with 1:1 regulator set at 43.5psi hooked to boost only source, pump rewire, bottleneck fix with 6an feedline all the way to the regulator, and Walbro 255 pump.
Yes, I have a gauge on the regulator and for right now I have one coming off the rail and taped to the windshield so I can see what going on when I rev it. Both read 43.5. Also I have 750s and a 50 trim but they have been scaled by TDSAaron.
Pretty much everything is new. Entire engine, tune, fuel system, ect its all new. I just noticed the idle issue today but I have done the RL, tune, bottleneck fix, and 4306 spark plugs since last time I started it.
Whats your fuel pressure when driving? Is AFR good in closed loop operation? What are your fuel trims? Is your fuel pressure rising when in boost?
Throw you stock injectors in, flash back to your stock tune, adjust the fuel pressure and see if it idles properly.
Have you talked to TDSAaron about it? It could easilly be the tune.
I have reset the PCM. Fuel pressure holds at 43.5 while reving but I have not driven it yet since the recent mods. I noticed I had this problem so I wanted to find and fix it before I get out on the road and possibly have a problem. Havent had stock injectors for a while but I will try my old tune with a steady 58psi and see what it does.
I have not bothered Aaron with it yet because its a new problem and I know he is pretty busy. If I cant narrow it down pretty quick I will ask him about it.
Every time I start the car it will idle @14.7 A/F but then after about 10 seconds the cars sound will get deeper and the wideband will drop to 10.0. It will come back to maybe 11.0 but never above that at idle. When I rev it up the A/F acts normal and stays in a normal range but once it comes back down to idle the A/F drops like a rock back down in the 10.0 range. I can shut off the car and restart it and it will do the same thing.
Vacuum is a constant -18 which is normal for this car. RPMs stay solid and it doesnt speed up or slow down like a bad TPS wire.
Its in the begining tuning stage right now so it could easily be in the tune but since it starts out correct and then goes south it has me wondering.
Any ideas?
Get the tuner to look at the tune again and make sure that you don't have a corupt file. We have had this happen a few times now and its a major pain in the ass to detect. I would have your tuner build you another tune off your base file and then send that over to you to make sure the file is good. If that runs like crap, then I would return the car to stock, send him another base file, then start over.
You could also have a bad O2 sensor so if you could data log the o2 volts so we can look at them, that would be great.
Every time I start the car it will idle @14.7 A/F but then after about 10 seconds the cars sound will get deeper and the wideband will drop to 10.0. It will come back to maybe 11.0 but never above that at idle. When I rev it up the A/F acts normal and stays in a normal range but once it comes back down to idle the A/F drops like a rock back down in the 10.0 range. I can shut off the car and restart it and it will do the same thing.
Vacuum is a constant -18 which is normal for this car. RPMs stay solid and it doesnt speed up or slow down like a bad TPS wire.
Its in the begining tuning stage right now so it could easily be in the tune but since it starts out correct and then goes south it has me wondering.
Any ideas?
Something is up with the LTFT/Closed loop/Upstream O2 sensor. When the car starts there's a delay before the PCM starts to use the O2 to adjust A/F. This delay, when the PCM ignores the O2 sensor, is when your A/F is fine. When the A/F goes rich the O2 is telling the PCM that the A/F is too lean and to add fuel. The reasons why its doing this are unknown. Bad sensor, bad wiring or exhaust leak are a few possibilities.
I need to see a datalog to confirm--be sure to use the reccomended PIDs and include 1/1 O2 voltage as PTP has suggested. If the O2 voltage stays low(ie lean) after proper warm up somethings up.
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Send me a datalog to look at for you. I looked over your last tune and it should be close. If your startup AFR's are good then your having a closed loop issue for sure. Like some other have already said, could be O2 sensor, wiring or exhaust leak upstream of the O2 sensor.
The datalog should start before you start the car and allow it to run for about 30 seconds after you notice the idle afr's change to rich.
Here is a log of me starting the car and this time it went straight to rich (10.00). After a a little bit it went up to 11.0 but then I gave it some throttle and it drop straight back to 10.0 and stayed there. Even when I reved it up it was real rich and stumbling some. Deposit Files
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14.7 idle then goes rich?
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