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Old 03-22-2011, 07:20 PM   #1
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Default LEAN bogging when cold

Help me solve this issue!

Last week I solved my idle problem. Ever since then I have been having a very strange issue with my tune. When the engine is cold (below about 130*F) it will still start and idle fine, but under ANY load it goes LEAN and bogs. AFRs go strait to 20:1 and the car does not want to move. After it finally gets to where I can move it still is extremely lean, but the issue seems to go away above 4k and the car rockets to life.


The car runs fine when it is up to temp. It also ran fine last week when I started it up in 60*F weather.

Attached are 2 logs

Log1 shows from start up , a 3 minute drive down the road with the issue never going away

Log 2 shows after it sat and idled for 2 minutes after the first drive. Everything is normal

My warmups look good, my fuel table is decent once its to temp, my spark looks good... WTF is causing this.

BTW I did turn on Idle Advanced and set it to 22* after the car is warmed up...but that doesnt seem to be related.
Attached Files
File Type: xls lean issue1.xls (443.9 KB, 74 views)
File Type: xls lean issue 2.xls (309.8 KB, 59 views)
File Type: msq 3-17-11.msq (34.6 KB, 75 views)
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Old 03-22-2011, 09:34 PM   #2
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Part of me wants to say bad coil but that would mean fuel isnt being burned and its too RICH.

INPUT?
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Old 03-22-2011, 10:09 PM   #3
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If fuel isn't being burned, then unused OXYGEN is making it to the O2 sensor, and you'll get a lean reading, even if you're too rich. (The O2 sensor doesn't read fuel-content, but rather oxygen content....get it "oxygen sensor"? )

Your plug wires need changed, your car isn't firing on at least one cylinder. It probably runs slightly rough.

Other possibility is stuck-open injector.
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Old 03-22-2011, 10:11 PM   #4
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i have COP's. I suspect a coil is just acting up when its cold. I have 2 spairs in my trunk. I will start the process of elimination and see if that works
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Old 03-22-2011, 10:16 PM   #5
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And there has been a past suggestion that a failing fuel pump can be the issue, though my experience is that fuel starvation happens at higher rpms, not lower.
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Old 03-22-2011, 10:19 PM   #6
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Yeah I doubt its the fuel pump because if you look at the log it idles fine but the second there is ANY load it bogs... even with very little load.

I hate warmup issues. you can only diagnose them 1 or 2 times a day and then you have to wait.
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Old 03-22-2011, 10:23 PM   #7
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Start the car and make it bog for several seconds, then turn it off while still cold

Then find out which spark plug(s) is(are) wet.

If you can make a spark plug wet for you (you're more of a man than I am, but also), you've just eliminated 75% of your waiting.
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Old 03-22-2011, 10:24 PM   #8
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I like your logic sir. lol

unfortunatly CT is getting hit with a bit of snow tomorrow so the chances of me touching the car is slim to none.
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Old 03-24-2011, 07:36 PM   #9
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This issue is really strange. So went outside today and it was about 40-45*

As suggested I started it, drove it in a circle for like 30 seconds just to get it to bog, then pulled all the plugs. None were WET. they were all evenly black (i run a bit rich). I put Brand New BKR7E's in and started it back up. . .

Same issue. one by one I disconnected the coils. All seemed to have similar effects (surprisingly very little effect actually)

Then I disconnected the injectors 1 at a time. Same thing, none seemed stand out as being different than the others. By the time I reached the last injector the car had warmed up enough where the problem was completely GONE.

I am gunna go back to an old tune tomorrow and see if it magically goes away. I dont get how this issue simply started after I changed some IACV settings and added idle advance (which isnt activated when its cold).

Ideas??
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Old 03-24-2011, 07:38 PM   #10
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Edit: I might hook up a manual fuel pressure gauge to it at some point and make sure the pressure goes up as I rev it. I did recently have the carpet out of the car...maybe I messed with a wire?
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Old 03-24-2011, 09:28 PM   #11
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is your mat correction pulling lots of fuel?

make sure warm up isnt below 100%. sorry if this has been mentioned. reading all posts on my phone is s pain
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Old 03-24-2011, 09:34 PM   #12
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Thanks for the input. When you get a chance check my logs tho.

GammaE and warm up enrich are well above 100... MAT correction shouldn't be pulling anything...but I might try turning it off for *****.
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Old 03-24-2011, 11:33 PM   #13
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I noticed in you exhaust settings you have it set to wideband, but in your tunerstudio properties you have it set to narrowband.

What does 4.96v convert to in AFR? that's what a lot of your afr table is set at.
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Old 03-24-2011, 11:55 PM   #14
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I dont use tunerstudio. I use Megatune.

I have PLX 0-5V (10:1-20:1) ..so 4.96 is ******* LEAN AS HELL
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Old 03-25-2011, 10:25 AM   #15
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Quote:
Originally Posted by 240_to_miata View Post
I dont use tunerstudio. I use Megatune.

I have PLX 0-5V (10:1-20:1) ..so 4.96 is ******* LEAN AS HELL
then that sounds like your problem. If you have your wideband authority set to allow a large change, then it is trying to meed the 4.96v you have in your afr table. Leaning out the car until it dies.
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Old 03-25-2011, 10:28 AM   #16
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I think your settings are wrong when u are looking at my file. My afr tables are normal. And my closed loop isn't active till above 130*f anyway

Most of my off boost afr table is 15:1
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Old 03-25-2011, 10:32 AM   #17
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You are probably right. I used tunerstudio, so I opened it up in that. I'm also not familiar with ms1.

Which sucks, because that was about the extent of my knowledge :( Sorry I couldn't be any help.

Did youcahnge the fuel filter? I had a old subie that would rn for a litte while, then choke out and die. Filter so so full of crap that when it settle it allowed fuel to pass, but then the fuel swirled aroudn th egarbage until it would clog. I cahnged fuel filter and all was well.
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Old 03-25-2011, 10:33 AM   #18
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Thanks for digging into it anyway
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Old 03-25-2011, 11:02 AM   #19
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Quote:
Originally Posted by 240_to_miata View Post
I think your settings are wrong when u are looking at my file. My afr tables are normal. And my closed loop isn't active till above 130*f anyway

Most of my off boost afr table is 15:1
About what temperature is your engine at when it starts acting normal?

Throwing unburnt fuel out of the exhaust?
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Old 03-25-2011, 12:08 PM   #20
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About that temp actually... 130ish

It just confuses me because these warmup and ego settings have always worked in the past
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