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Old 08-26-2009, 01:54 PM   #1
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Default MS likes to lean idle and part throttle cruise out over time.

I'm stumped and hoping this is just the result of some setting I've neglected to enable or faulty sensor somewhere.

When I first flash a new .msq (like after VE analysis) the car will idle on the rich side when cold and lean to between 14:1-14.7:1 when warm. Over the course of the next few days cold start will see the AFR gauge (AEM) start around 16:1 (cold!) and then drift off-the-charts lean until warm, and then idle around 17.5:1. As you can imagine, this makes for a very un-smooth exit from the neighborhood in the morning especially. Boost is still solid in the 11:1-12:1 area.


Things about the car that could possibly be clues:

I have no idle valve, not running EGO correction currently, have the GM AIT just after intercooler where it won't get heatsoaked. My alternator and/or battery are likely on their last legs.
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Old 08-26-2009, 02:32 PM   #2
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Try data logging both a good start and a bad start. Is the pulse width any different? How about the temperature readings?
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Old 09-07-2009, 07:26 PM   #3
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Thanks for your attention to this Matt, I appreciate it and should have gotten a reply to you sooner.

I've taken two logs, the first I took and tried to showcase the way the car likes to try to bog with any stab of the throttle. On that log I hit the spacebar before each blip of the throttle.

The second log was me idling the car and re-parking it after a wash just now. I'd been idling it for a couple minutes an hour or so prior, to explain the relatively high coolant temps. Tried to find vacuum leaks again, using the carb cleaner method. Nothing. I double-checked the ground for the WBO2 also, it's good and still where Jerry recommended I place it when I was there (co-located with the ECU's on the valve cover). There's almost a full point's worth of discrepancy between the WBO2 display and the gauge in Megatune (leaner in Megatune)!

Edit - Guess due to Paypal's error and my subsequent subscription lapse, I can't post my logs thanks to my upload quota being exceeded. Grr...
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Old 09-29-2009, 09:06 AM   #4
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It's been wearing on my mind that this smacks of an injector issue. Was reading in GRM that symptoms like mine (WOT AFRs good, poor driveability and idle AFR consistency) was injectors most of the time. I have the budget ATM to get some new RCs to rule this out. Worthwhile?
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Old 10-04-2009, 05:51 PM   #5
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Hey Koto -
I have the exact same symptoms. I just went megasquirt, and did not have the idle AFR issues when cold prior to megasquirt. Does that say it's not the injectors?

I've cranked up my warm up enrichments, and boosted all the idle cells in the VE table. I still have a bad lean condition as I get above 160 degrees, but below being fully warmed up. I was going to force the warmup enrichment to act until 175-180 degrees as a cheat.


I'd be watching this thread with interest to see what you figure out.
Jim
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Old 10-04-2009, 07:39 PM   #6
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I've bought some used red-tops off of a member here, going to swap them in and report whether or not that fixed it.
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Old 10-04-2009, 07:50 PM   #7
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welcome to heat soak. Mine does this in traffic, but 30-seconds of 40mph and the problem goes away.
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Old 10-04-2009, 11:35 PM   #8
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Nah, can't be heat soak since it'll do this dead cold on occasion and it doesn't get better once I get moving. My AIT sensor isn't in a position to get soaked anymore either.

Injectors ought to arrive mid-week.
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Old 10-19-2009, 10:41 AM   #9
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Hey Koto,
Did you get the new injectors in?
Any change in behavior?
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