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Old 08-12-2004, 02:25 PM   #1
cdvma
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Join Date: Jul 2002
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2002 PSM WRX (Sold)
2009 BMW X5

Default Running real rich at startup

Quick thought: my UTEC is tuned without injector scaling and my car runs really rich for the first 15 to 20 seconds or so after I start it up. Would scaling the injectors and fixing the fuel map cure my rich condition? When the stock front O2 sensor warms up and the fuel trims are applied its ok.

I have no problem doing this, but I just dont want to if all the trouble isn't going to fix it.

Relevent setup:
Chopped stockers
UTEC fw. 4.2
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Old 08-12-2004, 02:41 PM   #2
big_adventure
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This is a very common problem with chopped stockers. As far as I've seen, people have tried all sorts of fixes. Something that might help a little: turn the ignition on but don't start the car. Wait for 30+ seconds. Then start it. This gives the O2 sensor heater circuit time to heat up before you start it. The ECU doesn't listen to a cold O2 sensor. Kind of like my girlfriend when I tell her I'll only be working on the car for "an hour".

You can turn on OLF and scaling, but it's not going to solve the pre-O2 sensor rich condition.

-Sean
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Old 08-12-2004, 02:46 PM   #3
cdvma
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Yea thats what I was affraid of. I dont mind letting it warm up for 20 seconds or so, but it does get annoying very quickly. My normal routine is to wait for oil pressure to build, then I back out of the driveway. When moving the AFRs are good because by the time I get out into the street its pretty much warmed up. Oddly enough as well, giving it a little rev will "clear" it right up.
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Old 08-12-2004, 03:22 PM   #4
TurbojonLS
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Quote:
Originally Posted by big_adventure
The ECU doesn't listen to a cold O2 sensor. Kind of like my girlfriend when I tell her I'll only be working on the car for "an hour".


I've just started telling my wife I'll be working all day. No matter how long I think I'm going to take, it always ends up being at least twice as long.
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Old 08-13-2004, 05:14 AM   #5
skywalker
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Just a thought but when you start the car up in the morning, the car needs to run richer for startup conditions. You will notice the RPM starts around 1500 and drops to idle once the car has fully warmed up. The car needs to rise to a certain water temp level needs, I believe 70 degrees Celcius, before leaning the car out to Stoich levels. This is the reason why you should run you car first for a few minutes before getting your car smogged, so the ECU can adjust the car to the correct A/F ratio by letting the car expand.

I usually let my car warm up for a few minutes before driving anywhere. Forged internals take a litle longer to warm up.

Cheers,
Bill Knose
Lead Tuner
I-Speed USA
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Old 08-13-2004, 07:32 AM   #6
cdvma
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Bill,

You are correct, in that it will run rich for a bit but its sometimes at the point where its stumbling on itself. Not much to the point where it sounds like its loping but its noticeably different from just a abnormally high RPM warmup. The injectors are twice the size of stock so its just dumping a little too much. By the time I'm done putting on the seatbelt, releasing handbrake, putting it into reverse, and on the clutch the sensor is almost warmed up so its not that much of an issue.
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