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Stuttering: runs lean and plugs are white.

 
Old 03-28-2009, 12:51 AM
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Default Stuttering: runs lean and plugs are white.

Ok cross posting this problem again with m.net because i am not getting much traffic there.

Here is the problem:
The car first started to stutter once in a while when idling or when cruising. Today it would barely idle. It sounds like its running on few that 4 cylinders. I have i wideband and as soon as its starts stuttering the wb goes to 20afr.

When i press on the gas the car barely accelerates and sounds like a motorcycle. I got home and shut the car down. I could here the exhaust crackling, so knew it was hot as well.

I pulled the plugs and the cyclinder number one plug was almost white at the tip same for the number 3 but the rest were ok. I started the car back up and when i moved the plug that connects to the coil the car stuttered just like when i was driving and made the same noise. i moved the plug around and more i moved it more it did it.

Does it look like my coil is shot? is there a way to check?

I logged the car with megatune and everything except afr looks fine?

If the coil is bad why afr would go so lean like that?

I really need some input.

I am including a log that i took when the car was stuttering.

So i was wondering if it was a coil wouldn't the car run rich because the fuel would not get ignited? So its more likely its the fuel pump or injectors?
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Old 03-28-2009, 12:56 AM
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looking at the log it looks like when the car starts to stutter the fuel pressure goes all the way to 64 so something is got to be going on with the fuel.
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Old 03-28-2009, 01:03 AM
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I don't believe your MS reads fuel pressure....
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Old 03-28-2009, 01:06 AM
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Originally Posted by turbobluemiata View Post
I don't believe your MS reads fuel pressure....
well i am not sure how accurate it is but its got a tab that says fuel pressure.
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Old 03-28-2009, 01:08 AM
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there is no sensor for that so disregard those values
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Old 03-28-2009, 01:09 AM
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also afrs look like they go rich, not lean
edit: which could indicate a bad coil if you've got 2 wet plugs and 2 white plugs and 9:1's afrs
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Old 03-28-2009, 01:12 AM
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20 is lean not rich if i am not completely wrong here.
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Old 03-28-2009, 01:16 AM
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so what could be going on here?
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Old 03-28-2009, 01:16 AM
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Originally Posted by Rushin View Post
20 is lean not rich if i am not completely wrong here.
where are you seeing 20:1. at the end of his log he has a long period of very rich idle <10:1
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Old 03-28-2009, 01:22 AM
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when i look at it through excel i cant even find afr! But when i look at it it through megalog viewer i can see that i am in boost at like 3k rpm with afrs at 19 and 20. Thats when the car sounded really bad and i was going up a little hill.
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Old 03-28-2009, 01:24 AM
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i think the end of the log is when i unplugged the sensor to see if it was not running right. Thats why its like that.

And whats weird is that when afr says 21 the fuel pressure is maxed at 64 and then when afr goes back to normal and the car stops to stutter and goes back to 14.5 or so the pressure is down to 34-40 or so.

Can we safely say that this is most likely a fuel issue not spark? I just want to eliminate the spark and go right to the fuel?
Maybe first step would be to change fuel filter( even though i changed it like 5k ago) and run seafoam and if that does not help replace injectors and the pump?
I bought a set of 550cc injectors that will need to be cleaned anyway.
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Old 03-28-2009, 01:36 AM
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Originally Posted by Rushin View Post
when i look at it through excel i cant even find afr! But when i look at it it through megalog viewer i can see that i am in boost at like 3k rpm with afrs at 19 and 20. Thats when the car sounded really bad and i was going up a little hill.
in mlv, where exactly (seconds) do you see this. i don't see it, though i am drunk
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Old 03-28-2009, 01:37 AM
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i have a fuel gauge that i can stick in between the fuel lines, that should help me see if there is a problem right? I am not sure what i would be looking for. What is the normal idle fuel pressure? what should it be under acceleration?
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Old 03-28-2009, 01:39 AM
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Originally Posted by Mach929 View Post
in mlv, where exactly (seconds) do you see this. i don't see it, though i am drunk
Stay with me man, i need help here :-)

The best example is at 1222.036 and goes to 1224.618. the rpm is growing and the afr stays at 21

same is at 1240.815 to 1241
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Old 03-28-2009, 01:42 AM
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dude ms can't log fuel pressure if you don't have a fuel pressure sensor supplying your computer with information. so those fp values are meaningless.
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Old 03-28-2009, 01:46 AM
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Originally Posted by Rushin View Post
Stay with me man, i need help here :-)

The best example is at 1222.036 and goes to 1224.618. the rpm is growing and the afr stays at 21

same is at 1240.815 to 1241
you are lean in those areas but you're not even in boost. try working on your acceleration wizard
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Old 03-28-2009, 01:51 AM
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ok disregarding the fuel pressure and all, what could be cause this stuttering and afr going all the way to lean? I mean i was in the car and right when the car started to stutter i looked at my wideband gauge and in the ms and it was at 21. right when the car stopped stuttering the afr was back to normal. And i should say that the rpm gauge bounces like crazy from what ever rpm i am in to zero when this is happening.
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Old 03-28-2009, 02:03 AM
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bad coil or igniter IMO
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Old 03-28-2009, 02:07 AM
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Originally Posted by turbobluemiata View Post
bad coil or igniter IMO
that was what i was thing. how would i check for that? where is the ignitor btw? i will take a video of the car tomorrow and post it here.
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Old 03-28-2009, 02:39 AM
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passenger side by fuse box
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