Occasional rough idle? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-23-2007, 08:07 AM   #21
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Quote:
Originally Posted by Reverant View Post
Anyone "new" to the Megasquirt scene having this problem as well?
I've not noticed this problem as much latey, It's still happening, but I'm no longer running stock injectors, they're now (cleaned and flow-tested) 600cc injectors. I don't know if because of the loss in resolution because they're high imp injectors it's masking the problem slightly?
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Old 03-23-2007, 06:45 PM   #22
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As for your spikes and dips on the ignition output, that was taken VERY seriously and fixed quick. 029v or later fixes that right up. As for the random minor misfire at idle I'm not sure if I've experienced the same thing you guys have or not-- I do sometimes hear what sounds like a very minor miss at idle that I've never been too concerned about, I don't see evidence of a miss in the AFR datalogs (which would look like a lean spike in the AFR logs due to the unconsumed air in the pipe). At any rate it looks like James is looking into it based on the thread linked at the beginning of this thread. My experience thus far has been A) it doesn't effect my AFR so I'm not sure it's a miss, and B) it really doesn't seem to effect anything. But the bottom like is James is a wiz at this stuff and I'm sure he'll nail it. Definitely go ahead and run 029v or later though to get rid of those spikes and dips...
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Old 03-24-2007, 06:23 AM   #23
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Jerry,

I already run 029v, I also had the spikes and I participated in the "Ignition spikes under boost - scary" thread. As for the AFR, whenever the problem appears I do get leaner, from 14.7 to about 16-16.5ish. I'll scope the injector outputs today.

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Old 03-25-2007, 10:34 AM   #24
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Cool-- if you get anything useful scoping the ignition I/O I'd suggest posting the traces in that thread on msextra.com- James appears to be watching it pretty closely. At one point I had this going on with my MR2 but I haven't noticed it lately-- I'll see if it is and if so I'll bust out the PicoScope and get some traces for James myself...
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Old 04-24-2007, 03:19 PM   #25
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I have to bring this thread back up because I had the same problem for the longest time.

I have an MSI Extra High Res running on an Escort with a GTX motor (essentially a BP with lower compression) and GTR turbo pushing 16psi of boost.

Here's the issue with the rough idle. Our motors like to run rich at idle. And I mean 13-12.5:1 rich unless you oscillate from lean to rich. The MS O2 feedback controller is not setup like the factory one and will not oscillate properly causing idle roughness. Don't worry, your gas costs won't go up dramatically if you have a rich idle.

Do not run closed loop with the O2 sensor at idle. Turn on closed loop at 1200-1500rpm

Tune your VE table slightly on the rich side.

Watch your intake air temp/density compensation. MS starts to pull fuel above intake temps of 70F. This can be seen in the gammaE if I remember correctly. As you warm up the car, the sensor heat soaks not being representative of the actual intake temp. MS pulls fuel and you start to have a rough and unpredictable idle. Correct this by doing coolant temperature correction and ADDING fuel when the coolant is hot up to 1500rpm. Do this until the car runs smoothly.

At this point you should never have a rough idle anymore ... I certainly don't anymore. Hoeve, if you need to pass emissions, you have to change things a little or you will fail on idle.

When tuning the MS in general be aware of all its compensations ... little problems drove me nuts until I learned to watch all compensations and then everything became really simple. Hope this helps out.
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Old 04-24-2007, 07:43 PM   #26
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I agree completely that the BP likes a rich idle. I have had much better results w/ 13.5:1. The thing that kills me, though, is that the stock ECU manages 14.7 and holds the idle rock steady. Last night I started setting up a blended Alpha-N just for idle (<1250rpm). It is rock steady but my tune is still very rough. Alpha-N seems really touchy and a lot less error tolerant.

I've also found I had to enrichen the mixture at intakes temps above 100 F. I see than a lot when I idle for long periods in my garage.
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Old 04-24-2007, 08:00 PM   #27
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My stock ECU oscillated from 14.5-15.3 and kept the idle smooth. Does the miata ECU keep a steady 14.7?
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Old 04-24-2007, 08:31 PM   #28
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My stocker oscillated from 14.5-15.3 or somewhere close to that.
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Old 04-24-2007, 09:09 PM   #29
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Quote:
Originally Posted by cjernigan View Post
My stocker oscillated from 14.5-15.3 or somewhere close to that.
So the control is similar to the GTX engine ECU .... try what I suggested and your idle should be a lot smoother.
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Old 04-24-2007, 09:38 PM   #30
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i like to have mine at 17:1 and pretend that it is purring at me.
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Old 04-24-2007, 09:55 PM   #31
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Quote:
Originally Posted by Lex View Post
So the control is similar to the GTX engine ECU .... try what I suggested and your idle should be a lot smoother.
I might just do that.
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Old 04-25-2007, 12:49 AM   #32
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Poor wording on my part. The AF ratio oscillates but the rpm stays rock steady.
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Old 04-25-2007, 01:14 AM   #33
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the idle is maintained by the IAC valve ... but even without one the idle is pretty steady.
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Old 04-25-2007, 03:09 AM   #34
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Quote:
Originally Posted by Lex View Post
Here's the issue with the rough idle. Our motors like to run rich at idle. ~ Do this until the car runs smoothly.
~
At this point you should never have a rough idle anymore ...
Sorry, but you are plain wrong. The rough idle issue is tracked to a firmware bug. Specifically, one of the our injectors is randomly not opened/squirting, same goes for the coils/ignition. It has nothing to do with AFRs. I DO have a perfect 14.6-14.9 AFR at idle and the car runs BEAUTIFULLY. Just like stock, maybe even better at times. Perform a reset and it gets fucked up. Reset again and it propably is ok. Repeat N times within S seconds (with the IAT and CLT not changing more than 3* F) and the results vary tremendously. Its a software bug, not a tuning issue.

Jim
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Old 04-25-2007, 07:59 AM   #35
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Jim, maybe it's MS2/Extra time?
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Old 04-25-2007, 09:14 AM   #36
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Yes. I'm building a new block right now so I'm cash-strapped, but it's already planned.

Jim
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Old 04-25-2007, 11:26 AM   #37
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Quote:
Originally Posted by Reverant View Post
Sorry, but you are plain wrong. The rough idle issue is tracked to a firmware bug. Specifically, one of the our injectors is randomly not opened/squirting, same goes for the coils/ignition. It has nothing to do with AFRs. I DO have a perfect 14.6-14.9 AFR at idle and the car runs BEAUTIFULLY. Just like stock, maybe even better at times. Perform a reset and it gets fucked up. Reset again and it propably is ok. Repeat N times within S seconds (with the IAT and CLT not changing more than 3* F) and the results vary tremendously. Its a software bug, not a tuning issue.

Jim
Having it run richer I never have the occasional rough idle issue anymore. So what is your suggestion for a fix and how did you get your car to run consistently well at 14.7 afr?
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Old 04-25-2007, 11:26 AM   #38
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I bet MSII might be part of his answer.
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Old 04-25-2007, 12:02 PM   #39
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I'd love to know a different solution to a consistent idle. I have read on MS forums that even people with MSII suffer from a rough idle and no one mentions a bug.

Reverant, if you have some insight it would be great!
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Old 04-25-2007, 01:48 PM   #40
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Quote:
Originally Posted by Lex View Post
I'd love to know a different solution to a consistent idle. I have read on MS forums that even people with MSII suffer from a rough idle and no one mentions a bug.

Reverant, if you have some insight it would be great!
follow his link I have the same issue.
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