Idle Surge is driving me nuts - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-29-2010, 11:46 AM   #1
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Default Idle Surge is driving me nuts

Ok, it's probably easier than I make it out to be, but I'm fairly new to tuning and now there are too many variables and I'm impatient. I got my FM Hydra/Turbo installed and running good, no problems with idle until the cold weather blew in <50deg (I'm in Texas and that's cold). Now morning start up will fluctuate between 1,700 and 2k rpm until it warms up and then it's fine. I'm thinking vacuum leak, but since it goes away when warm, maybe a expansion/contraction thing? I did use the stock isolators on my RC550 injectors, could they be loose when cold? Could it be temp trims or post start enrichment? I set the ISC Min/Max to 0 and no change. It's hard to diagnose when it only last for a few minutes. I've got a 99head/intake on a 96 block. Maybe someone here has been through this before.
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Old 12-29-2010, 02:21 PM   #2
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it's most likely fuel mixture in the normal fuel map is not dialed in.

you'd know just by looking at a few datalogs.

it could also be that the idle control is switching on and off, but it's more likely the fuel.
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Old 12-29-2010, 03:02 PM   #3
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From what I understand, setting the ISC PW Min/Max to 0 turns it off and it made no difference, so I don't think it's idle control. I have not tried to datalog, since it only lasts a few minutes at first start up after sitting more than a few hours, but I'll try that. You think it's more normal fuel map that temp trim or post enrichment? It idles fine once warmed up or if outside temps are over 60. Is it more than likely a lean condition causing it? By the time the 02 sensors are warmed up, it goes away soon after that, so it's hard to tell. I had no problems at all until it got cold outside.
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Old 12-29-2010, 03:19 PM   #4
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here's what you can do:

get in the car when it's cold and turn the key on (not start) and let the o2 sensor warm up for two minutes.

start a datalog at the highest rate.

start the car and let it warm up to the point where it stops oscillating.

stop the log

look at the log.
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Old 12-30-2010, 11:04 AM   #5
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A few questions:

what version of hydra?
what turbo (just curious bout the turbo)

As you guessed, Hydra uses more than just the ISC to control idle. There are also the coolant temp fuel trim and the coolant temp ignition trim maps. Adding/pulling fuel timing will affect your idle. There's also the post start enrichment and cranking enrichment.

First thing I would do is make sure your ISC valve/screw is adjusted aok. Let it warm up fully then disconnect the ISC plug. Twist the screw until the hydra-indicated RPM matches your idle speed target.

Also, before you do your log, let your wideband warm up- turn the key a few clicks or whatever (seatbelt warning should beep) and watch the wideband readout in the hydra. When it stabilizes at full lean, it's warm and you can log and start up. Make sure you log ISC, timing, afr, temps.

As y8s says most likely it is your fuel when warming up and you may need to mess with your fuel trim maps. Lean can really make warm up unstable.
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Old 12-30-2010, 11:58 AM   #6
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Hydra V2.5 and the turbo is the standard GT2560R.

I'll be able to spend some time on it this weekend and get some warmup datalogs.
I let it warm up in the driveway this morning and i noticed that it surged for a while, then stuck at 2k solid for a minute or 2 and then came down to normal idle with the brief pause at about 1200. Unplugging the ISC is not possible with it running, since the intake tubing is right in front of it, although when warm, Idle is spot on. My laptop battery was dead this morning or a I would have logged it.
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Old 12-30-2010, 08:05 PM   #7
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Also give Jeremy a call- you paid a premium for that kit so get your value with their support.
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Old 01-04-2011, 11:28 AM   #8
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Ok, after a long drunken weekend and needing to wait several hours to cool down between tinkering, I have noticed a few things. The surge goes lean to rich (11:1-16:1) according to the datalog and my extra AF guage in the car. I thought it could just be caused by being lean, but rich causes it also. Does it go lean and dump fuel causing a rich surge or does it go rich and fuel cut causing droop and lean?? I have managed to get a solid idle a little sooner during warm up, but it sticks at 2k. That also causes it to periodically stick at 2k when warmed up (14.5:1). If I lean the cell it should be in at idle (not the current 2k cell it is currently in) the idle may drop smoothly down to 900 when warm (13.9:1). It's like the isc is cutting off for the 1k droop to idle, so I'm wondering if I also have a problem with my ISC valve. It seems to be a fine balance between cold start and warm idle, so the post enrichment and ISC are my focus at the moment. It's just so many variables in a short cold warm up period, when i'm not sure all mechanical systems (ISC) are even good. It seems the ECU shouldn't be this picky and the action of making the ISC kick on/off is what i'm searching for. Just some more senseless rambling while I get used to the new system.
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Old 01-04-2011, 05:47 PM   #9
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At lunch I solved the warm 2k idle by raising the max vacuum in the isc setting from 573 to 600. I'm not sure what that does, but it seemed to help it calm down to idle nicely with no hangup at 2k.
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Old 01-04-2011, 05:51 PM   #10
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Dude your **** is going to get way out of whack. Just read the Hydra manual and it will tell you what all the various settings mean.


Where in TX are you?
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Old 01-04-2011, 06:37 PM   #11
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Nah, I have safety files saved that I can revert to. every time i think I've made too many changes, I load one of the older files and start over. There are so many variables that I try to only adjust one at a time until I get a result. Occasionally I'll change a couple of variables and try it out. The hydra manual does give basics of what things mean, but not so much what triggers some of them and how they react together. Also, unless I print it, you can't have the hydra software and hydra manual open at the same time. I guess it's not a common problem since i don't see many answers, so i'm learning as i go. i'm in the fort worth area.
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Old 01-04-2011, 06:39 PM   #12
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Quote:
Originally Posted by customstreetmachines View Post
At lunch I solved the warm 2k idle by raising the max vacuum in the isc setting from 573 to 600. I'm not sure what that does, but it seemed to help it calm down to idle nicely with no hangup at 2k.
max vacuum should be set so that in all normal driving conditions, when you take your foot off the gas while coasting (in or out of gear), the idle valve doesn't open and make your car do crazy cruise control acceleration when you expect it to slow down.

about all it does is set a point where the ECU knows that it should start doing idle control.
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Old 01-04-2011, 06:56 PM   #13
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I remember the manual mentioning that too low of a setting could cause high idle, so raising it a little couldn't hurt in my mind. Although i'll tinker with that so i don't get a droop from going too high. i'm just working my way around the system to see what each parameter does when I jack with it. I built a fairly custom engine, so I knew it would take time to dial in. I'm just impatient when I can't diagnose it right away.
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Old 01-15-2011, 07:52 PM   #14
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I know you guys can't sleep from the anticipation, so the idle issue is solved. It was the idle valve. It ohmed out good and functioned, but i couldn't tune out the issue with fuel. I popped for a replacement throttle body and now it idles smooth as a kitten.
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Old 01-16-2011, 03:04 AM   #15
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wow not what i expected. **** yah nig, go you!
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Old 05-04-2011, 07:02 PM   #16
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Quote:
Originally Posted by customstreetmachines View Post
I know you guys can't sleep from the anticipation, so the idle issue is solved. It was the idle valve. It ohmed out good and functioned, but i couldn't tune out the issue with fuel. I popped for a replacement throttle body and now it idles smooth as a kitten.
The hydra holds the valve hard open just dumping current when the car is key on engine off which can lead to premature failure. I haven't gotten the idle circuit to work well in all conditions yet, it is very messy at best and the PID control seems to be pretty poor. However, it hasn't been high on my priority list as it starts and works now. So... since most of us have setups that probably have similar idle conditions:

Anti-lag ISC Postion: 10.1
Moving vehicle ISC min (%): 10.1
ISC max duty: 85.0
ISC min duty: 5.1
ISC max vacuum (mmHg): 621
ISC stepper steps: 25
ISC P-term: 160
ISC I-term: 100
ISC D-term: 10
ISC AC anticipate (%): 50.2

I idle around 800 rpm instead of the FM programmed value of 952rpm once warmed up. Also the upper learn limit was maxed at 60 when warmed up and lower learn limit was 24 when warmed up which I changed to 100 and 0 respectively.

For those that are happy, what settings are you using?
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Old 05-06-2011, 10:49 AM   #17
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I'm not happy with my idle per say, but it's close enough for now. One of those low priority issues that will get me by while I get everything else up to par. I'd be interested to know if anyone is actually happy with their settings.
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Old 05-06-2011, 11:21 AM   #18
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Quote:
Originally Posted by customstreetmachines View Post
I'm not happy with my idle per say, but it's close enough for now. One of those low priority issues that will get me by while I get everything else up to par. I'd be interested to know if anyone is actually happy with their settings.
Given the same motor with such overwhelming similarities during idle condition, the settings should work well from engine to engine. Having a different turbo, intercooler, etc should generally not effect these parameters.
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Old 05-06-2011, 11:55 AM   #19
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Well for me, I have a 96 block w 9:1 pistons, 99 ported head, 96 Throttle body, no egr and several other differences besides the standard barometric pressure and temp differences everyone has. I would think most people on here have enough mods to make a difference, so I'm different, just like everyone else.
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