I haven't found a thread on this EXACT problem....

I'm not a fan of driving cars that aren't warmed up, however....

When I start the car and let it sit till the needle is up to normal temp (180F I believe), I have no trouble, but if I try to drive the car at all before it is up to normal operating temp, the idle surges from 1000 to almost 2000 rpm until the car is all the way warmed up.

It started this after I tried to adjust the idle down with the set screw on the tb, (It was when I first got the car, I didn't know that wasn't the proper proceedure at the time)

Now that I have ecuflash, I can manipulate the idle to idle fine when warm or before driven, but the same problem still exists, only before its warmed 100% of the way up

I'm wondering how I go about getting this to stop, any ideas?

 

i have the same thing happen on my car. i think the car wants to do that to circulate the oil. My oil pressure gauge shows 100psi at idle when i first turn the car on, but it goes down to about 15-20psi once warmed.

I think its normal...

 

It kind of does correspond to when the water thermostat opens....

I was under the assumption it was something I did, I don't remember the car doing this until I messed with the idle screw.... I did that because the car was bone stock and idling at like 950 warm!!

 

Look at the tables under Idle..

There are several Desired ISCV Initial step tables and desired idle speed..

If you altered the BISS (the set screw on the throttle body) the stepper settings are thrown off a bit, you should set the BISS back to 700rpm and work from these tables, but you can see they are coolant temp dependent and will alter idle as the coolant temp changes. The ISCV initial step is where things are a little funky, I see this sometimes as my coolant temp is lower than closed loop control allows, so it sort of sticks on the stepper settings instead of trying to target the speed. I also think this happens if the range is outside of the steppers correction range. But think of it more as a "Choke" where when its really cold, the engine tends to run a little richer and higher RPM until coolant temp rises..

These are all adjustable parameters.. Their just not as well understood as they really should be.

 

Oh, Another thought..

If you have a mini battery that isn't taking a charge well, the car will idle higher to try to charge the battery.. Not sure where to make that adjustment, but I just noticed this a few weeks ago when my old Mini battery took a dump (Became sulfated and stopped taking a proper charge) so Id get very weird idle issues that I never had before, not to mention cold start the car would idle around 2500rpm.. When I replaced the battery the problem went away.

 

If I wanted to reset the idle screw to where it was, how should I start, I have my idles all set for 977 , (Comp 280's) for any value that was less than that on the stock map.... what do I have to do, set all those back to stock and then try to turn the idle to 700 with that screw then use the target idle rpm to raise it back up?

I think I have to address that before I can change any ISCV values, no?

 

I don't remember after all this time, but I would look in the service manual to see, though I think you might need to run a test mode to reset the stepper so you can set the base idle.. In my case, I closed it all the way, and I think I opened mine 3 full turns and it was okay again..

In reality, see if you can remember how much you adjusted it previously and try to undo it.. The only reason I sugges that is because it'll mean you won't have to play with the ISCV settings much, but you can just start by adjusting the ISCV settings until you get something that works for your car.

 

Ok, I will try to turn it all the way in and then back out 3 turns and see where the idle sits, am I trying to match my biss with the ecu target warm idle, or is the "base idle" suppose to be the lowest and then the ISCV raises it from there as it sees fit for the cold air (like a choke)

so that would be why messing with the biss throws the ISCV off because they are matched to work from the base idle setting and up, maybe mine is screwed up b/c the set screw is backed out further than it needs to be?

 

I think the best thing is load in a Stock Evo 8 flash and then adjust the biss till its 650rpm
then reload ur exsisting flash and then tune the iscv and idle

 

my idle starting from cold, is arpund 1600rpm but very solis without flactuations...

Gradually while warming up it falls to around 800-850rpm...

Note that i have Cossie cams on the car...

Dynoflash did a great job...!!!

 

I tried ALOT of stuff lol, now I have two problems lol,

I have the "surging" now whenever the car is moving and I'm off the gas. As in, if I'm driving and then let off the gas/push in clutch, or put in neutral and let off clutch.

It idles ok when stopped for the most part, occasional rise up to 11 or 1200.

I tried the flash to stock idea to reset the biss, and now I've gone back to my map and tried adjusting the ISCV up 5 on each map accross the board.

I'm wondering how do I know if the ISCV are to high or low? what do the values actually represent? how much the valve is opened?

I'm contemplating going to mitsu and having them reset the biss, want to see the look on their faces when they hear the 280's rofl

Anyone have an idea on getting that BISS close enough to where it needs to be without going there?

one other thing, on the tables, what does "drive" and "neutral" really mean, is it looking the see if the car is moving or not?

 

I was reviewing some logs from my car at idle, the way it's set the ISCV value is at 62, it looks like when I started raising the idle the values went down to 55, when the idle was lowered, it went up to 64... so It's trying to open the intake enough to hit my target idle, compensating for the biss setting, right?

What ISCV does anyone else read at their target warm idle? (Is there a way i can shoot for a target number on there using the biss and the iscv steps in ecuflash?


EDIT: also, if it matters, my low fuel trim is at 100, mid is 98, and high is 130 at idle, the o2 feedback trim stayed above 100 (closed loop I think?) MOST of the time, it occasionally went under (and then the second o2 would disappear)

EDIT2: looks like my fuel trims are great then, so I'm still looking for someone else's ISCV step values (Logged from evoscan) hopefully I can compare to mine and get the idle back under control.... anyone on what those should be sitting at during warm idle?

 

I have some logs of cold start and drive, warming up to full temp, and some driving with the idle surging after the clutch is pushed in from about 45mph, and then 65mph...

the iscv steps are in the 80's cold and 60's warm when the gas is off.... when the idle starts to surge, the o2 feedback goes nuts, from 100 to like 140+ very quickly in time with the surging.

I don't know where to host the logs, I'm waiting on flyin miata to give me my license so I can use it to look at the data, this is difficult using just evoscan

 

on DSMs these symptoms indicate either a bad ISC(Idle Step Controller), or a worn out o-ring on the BISS(Base Idle Set Screw).

 

I did this again today, I flashed to stock and turned the biss all the way down, my car just doesn't idle at 650, even when it was stock it didn't, all the way down it was still about 800, I flashed to the current map and the idle picked up to target, but there was surging and the idle was sensative, when I shut my hood it almost stalled lol

I've settled on one half turn up, it doesn't surge that I can tell from the tach or by ear under warm operation, it did surge one time when I turned on the defost.... but it was much more acceptable than before... and there was no hint of stalling after an attack on the gas tank....

My idle is target at 977 now, with ac on or off, drive and neutral... I may be able to lower it some, but seeing as my car idled so high stock, I think this may be a "well-enough" solution for now.

But If Malibu or someone wants to chime in and explain some of those ISCV values it would be educational, although I think I've learned a little bit already!