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Old 05-04-2009, 05:20 PM   #1
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Default Idle droop, engine stalls

It seems as I am having a heat related idle droop problem.

'92 N/A, MSPNP, LC-1, GM IAT, MAF removed.

MSPNP installation is fairly new, I have sorted the basic issues and am famliar with MLV and tuning my VE tables. Idle during warm up is rough, the car stutters and hesitate when I go from off to on the accelerator. When warm idle is fairly stable with AFR around 14. At some point the idle will droop and the engine stall from time to time. It's not directly related to the MAT but seems to be heat related as it often happens after some low speed driving.

I have tried to tune the deadband range plus the upper and lower rpm limits to no avail.

Idle dc is between 18 and 28.

The idle droop is clearly visible in attached log (including a full stall). MSQ is also attached.

Any suggestions will be highly appreciated.
Attached Files
File Type: xls datalog200905042101.xls (704.6 KB, 75 views)
File Type: msq 0405tune2.msq (34.9 KB, 72 views)
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Old 05-04-2009, 06:49 PM   #2
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I hate to be this guy, but you have a lot of reading to do, mainly the stickies at the top of this forum. The stickies plus a bit of searching will learn you good.

You need to retrofit a variable TPS to your 1.6 throttle body. 2 resistors will need to be removed from the MSPNP. This way when you snap the throttle closed, the megasquirt will know immediately and quickly adjust the idle DC to compensate.

In the interim, you can richen up the cells below idle so that if it droops, its less likely to stall. Also, increase your idle a bit via the idle screw. It'll be annoying for awhile having a 1k-1.1k idle, but i guarantee you'll never stall again.

Edit: Spoon feeding FTW. 90-93 Idle Droop and Stall Issues
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Old 05-04-2009, 07:13 PM   #3
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Well, sacred are the enlightened.

Sorry for being a dumbass, but it was not logical nor clear to me that the TPS mod was a non-option. Which it apparently is. NO 1.6 without a linear TPS or you asked for it.

OK, I will hurry to fix my TPS mod while trying to cope with the embarresment of having asked a silly question.

And BTW, thanks for the reply
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Old 05-04-2009, 07:16 PM   #4
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Quote:
Originally Posted by Viggoman View Post
Well, sacred are the enlightened.

Sorry for being a dumbass, but it was not logical nor clear to me that the TPS mod was a non-option. Which it apparently is. NO 1.6 without a linear TPS or you asked for it.

OK, I will hurry to fix my TPS mod while trying to cope with the embarresment of having asked a silly question.

And BTW, thanks for the reply
Dude, i'm sorry. Like I said, I hate to be "that guy". Mostly just trying to teach you to fish.
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Old 05-04-2009, 07:29 PM   #5
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Originally Posted by wayne_curr View Post
Dude, i'm sorry. Like I said, I hate to be "that guy". Mostly just trying to teach you to fish.
Hey man, dont be sorry,. You responded and pointed me in the right direction, I really appreciate that. I did try to fish the forum for usefull informations, but my impression was the the idle droop issue was a monster with many heads. And it's not logical to me that the MS is unable to emulate what the stock ECU does pretty well, without using a linear TPS.
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Old 05-04-2009, 07:46 PM   #6
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Quote:
Originally Posted by Viggoman View Post
Hey man, dont be sorry,. You responded and pointed me in the right direction, I really appreciate that. I did try to fish the forum for usefull informations, but my impression was the the idle droop issue was a monster with many heads. And it's not logical to me that the MS is unable to emulate what the stock ECU does pretty well, without using a linear TPS.
Logically, without some kind of feedback from the throttle, the megasquirt doesn't know to kick up the idle DC until the RPMs drop past the point of no return. I'm pretty sure your MSPNP isn't even wired into your stock TPS. Your stock TPS is just an on/off switch.

With the VTPS you'll have better than stock idle characteristics. I still had droop with the stock ECU when going from high rpm to closed throttle. I put a VTPS from a BMW 2002 in my car (dirt cheap on ebay). Now days I have a crappy 1200 rpm idle cause my idle valve stopped working completely but I dont have any kind of droop or stall issues still.

Oh, I meant to mention something to do with your hesitation on throttle input. This is acceleration enrichment needing to be tuned. Also, if/when you get your VTPS, this will also be a thing of the past. Not to say that you cant fix that now with just map based enrichment.
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Old 05-04-2009, 08:26 PM   #7
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you have to clean the IAC valve and play with the settings. They're different on every car when they break 20-years of age.
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Old 05-04-2009, 09:02 PM   #8
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Originally Posted by hustler View Post
you have to clean the IAC valve and play with the settings. They're different on every car when they break 20-years of age.
Directed at me or the OP? I'm going to clean mine tomorrow but i'm not holding out any hope. I've read plenty of people mention that they cleaned it but still it doesn't work.
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Old 05-07-2009, 07:33 PM   #9
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Just a quick update. I've fixed the idle for now (TPS still underway) by adjusting the idle screw + tuning the VE table to an idle AFR around 13. Idle is very stable around 1.000 rpm and the droops has been reduced so it never drops below 800 rpm.
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