Idle issue..Crank..starts..stalls

[roh92cp]

Ok like the title says The car starts revs up kinda high, ISC duty goes to 65% then the idle drops and car stalls everytime when cold and most of the time when warm. I can only get it to run with peddle effort and even then its tricky. Very rich condition as my data log shows. I have set my idle with the proper idle procedure and I just got finished tunning my MAF curve yesterday and everything looked great. I spent alot of time at the idle volt points to get that A/F correct and yes I was in OL. I noticed today that after the warmed 185 ECT my idle A/F was again rich stays around 13.3 . I tried again to adjust those volt points in the MAF curve and they would not move the A/F no matter how much I swung the values and yes I was in OL again. Am I missing something here....LOL of course I am. By the way am new to BE/QH tuning.

[cgrey8]

It sounds like exactly what's happening to this guy in this thread:
what table / function is in control after start

However usually when an engine cranks fine, but then takes a dive to either sputters or conking out, it's usually diving lean, not rich. See if this thread sounds like what's happening to you.

[roh92cp]

It sounds like exactly what's happening to this guy in this thread:
what table / function is in control after start

However usually when an engine cranks fine, but then takes a dive to either sputters or conking out, it's usually diving lean, not rich. See if this thread sounds like what's happening to you.

Thanks for the link, my issue is by different in that I can't get it to idle with a blip of the throttle. I have to really work and hold the throttle for at least 2 to 3 minutes before it will lean out and stay lit on its own. I data log from the onset of this issue and its very rich the hole time 10 and 11 A/F and then after a couple minutes it leans out to 12's. The only time it comes out of it sooner is when its warm then sometime I can just blip the throttle a couple of times and it stays lit A/F in th 12's. I tried -40 % in all cell for Fuel start OL and it really didn't work. However I didn't disconect bat to reset KAM. So I'll try again.

[cgrey8]

You may have a problem of over-enriching after crank, but I would recommend a lot of the same procedures to get you going which is to simplify the Base OL table by making all the values in it more consistent and lucid across the ECT range and do the same in the Startup OL table. I swear if you look at those two tables, it seems like Ford had two different groups working on those tables where one group was counteracting the affects of another group. Why else would extremely cold conditions be commanding lean AFRs? Because the Startup OL Table is over-enriching.

Then you can do a better job of pulling the excess fuel from the Startup table and getting cranking AFRs under control enough that you don't have bad hunting during OL startup before you go Closed Loop and get the AFRs under control that way.

[roh92cp]

I've since noticed that my ISC duty cycle goes up to 78% when the car starts then it dies. ALso once I get it to idle and its warmed the ISC is only 18% at idle 780 rpm and any time I give it gas the ISC duty cycle goes up to 60% and allways to 78% during med loads part throttle. I don't know if this cold be related but it seems amiss.

[Cougar5.0]

The only ISC issue is the fact that 18% is the minimum which means your throttle blade is open too much at idle.

The startup issue could be a MAF or injector slope/offset issue. If you're too rich open loop, it can only be a few things.

[roh92cp]

The only ISC issue is the fact that 18% is the minimum which means your throttle blade is open too much at idle.

The startup issue could be a MAF or injector slope/offset issue. If you're too rich open loop, it can only be a few things.

Thanks Cougar for responding to my tuning needs. I have a 90mm T/B and the set screw is all the way in so blade is closed all the way and that was with ISC disconnected it idled at 750 ish like that.

[cgrey8]

Is there a hole in the thorttle plate that would be letting additional air into the engine even with the plate closed?

[roh92cp]

Is there a hole in the thorttle plate that would be letting additional air into the engine even with the plate closed?

No hole in the plate and I did a pressure test of my system with soapy water and 25 psi of pressure from the t/B to the lower intake. The only small leaks was at the throttle blade shaft and the TPS housing, but that was very minor and under 25 psi its to be expected I imagine. I have a Accufab T/B and those are about the best.

[roh92cp]

Yesss ...how sweet it is. My first real victory hunting down a tuning issue. This crank start stall issue has been pissing me off for some time now. I tried many things. fuel start OL tables, fuel base OL adjusting ISC dashpot, ISC decay rate, ISC crank nothing. Finally today I saw in the ISC startup airfuel multiplier and started messing with this. It took a swing of + 40% fuel before it even started to make a noticable difference. Adding 10% at a time I was almost ready to give up when on the 4th try the idle hung on just barley, ahh a warm feeling came over me. I added another 10% and now she cranks fires revs and hangs for a couple seconds and then settles nicely on a smooth idle. The blue is the area I made changes and you can see in yellow below it from what. Well I can rest for a while now. The next issue in my sights is that pesky random stalling when rolling to a stop light. Thanks for those who chimed in with there help.

[Cougar5.0]

I just kicked up FN826A and ISC RPM adder and time for startup issues I was having, but adding air via the ISC due to an excessively rich startup condition just doesn't seem right to me.

[roh92cp]

I just kicked up FN826A and ISC RPM adder and time for startup issues I was having, but adding air via the ISC due to an excessively rich startup condition just doesn't seem right to me.

Yeah Cougar that not the hole story, sorry. I did reduce start up fuel and base fuel tables which did lean out the start up, but that was only one piece of the puzzle. The car still would not stay running after startup so thats when I discovered ISC table for startup which has cured the problem.

[roh92cp]

Seems the issue has crept back in and the start stall has returned. The only thing I can think is that adaptive learned a way around the changes I made to the ISC startup airflow multiplier tables. I'm gonna try and reset the KAM and see what happens.

[roh92cp]

Allways the basic things get overlooked. Well I hope it lasts, but for now the idle is great no more stalling after cranking or when rolling to a stop light. Even under hard decel the idle is holding up now. And all I did was raise the idle 100 rpm to 850 with the T/B stop screw. I'm still keeping my finger crossed for now as idle problems sometimes return like a curse.

[86GT]

I think the issue is the long tunbe header that you mentioned to me. At an idle the HEGOs do not get to operating temps and then they will report a false signal to the EEC. The EEC then tries to compensate for the wrong reading and all goes to hell.

I have seen nothing but problems from long tubes. You either have to force OL at an idle or you have to reloacte the HEGO further up the exhaust. Ford places the HEGO on the fox body at around 18 inches away from the closest exhaust port. This allows the HEGOs to get to the correct temperature and so on. The further away the cooler they get. Some will argue that the HEGOs are heated. This is true but the heating is only for startup and then the exhaust is supposed to maitain the temps.

The other option is to use WB in place of the NBs. This will keep the sensors at the required temperature. The problem doing this is it will shorten the life of the WB keeping the heaters on.

At this point i would increase the HEGO delay function by 3 in all cells and then I would change the adaptive update table in the cells at an idle to say -82. Also change the cells at row 1 column 2 and 4 to -57. All of this will prevent the EEC from learning in the idle range. You will need to clear the KAMRF after doing this.

[roh92cp]

I think the issue is the long tunbe header that you mentioned to me. At an idle the HEGOs do not get to operating temps and then they will report a false signal to the EEC. The EEC then tries to compensate for the wrong reading and all goes to hell.

I have seen nothing but problems from long tubes. You either have to force OL at an idle or you have to reloacte the HEGO further up the exhaust. Ford places the HEGO on the fox body at around 18 inches away from the closest exhaust port. This allows the HEGOs to get to the correct temperature and so on. The further away the cooler they get. Some will argue that the HEGOs are heated. This is true but the heating is only for startup and then the exhaust is supposed to maitain the temps.

The other option is to use WB in place of the NBs. This will keep the sensors at the required temperature. The problem doing this is it will shorten the life of the WB keeping the heaters on.

At this point i would increase the HEGO delay function by 3 in all cells and then I would change the adaptive update table in the cells at an idle to say -82. Also change the cells at row 1 column 2 and 4 to -57. All of this will prevent the EEC from learning in the idle range. You will need to clear the KAMRF after doing this.

Clint I have shorty headers. So far the idle screw adjustment change is holding no stalling issues anywhere. Could it be this simple.

[86GT]

ok log IPSIBR. This is the KAMRF for the idle. You need to target 0.00000 on the IPSIBR. You can adjust the TB idle air flow (ITHBMA). Also log ISC and make sure it is not down to 17.5 while idling.

[roh92cp]

ok log IPSIBR. This is the KAMRF for the idle. You need to target 0.00000 on the IPSIBR. You can adjust the TB idle air flow (ITHBMA). Also log ISC and make sure it is not down to 17.5 while idling.

OK I logged the IPSBR at idle fully warmed and got -0.350 to -0.4 and the ISCDC was 36.44 so now what adjustments do I make in ITHBMA. Mine is 0.5500 now do I go up or down and by how much.

[roh92cp]

ok log IPSIBR. This is the KAMRF for the idle. You need to target 0.00000 on the IPSIBR. You can adjust the TB idle air flow (ITHBMA). Also log ISC and make sure it is not down to 17.5 while idling.

OK I logged the IPSIBR at idle fully warmed and got -0.350 to -0.4 and the ISCDC was 36.44 so now what adjustments do I make in ITHBMA. Mine is 0.5500 now do I go up or down and by how much.

I increasd ITHBMA from .5500 to .9900 and got the IPSIBR to -0.008 so I thought I was good, but then it just started sliding back down to -0.359 again. adaptive must be changing something. I even tried going further with ITHBMA and tried 1.599 and it held for a little bit then the IPSIBR slid back to
-0.350 again. The ISCDC increasd to about 50% at the highest ITHBMA. I just set the ITHBMA back to 0.5500 and now ISCDC is 38%. So what gives am I doing something wrong again. Why won't my changes stick.

[86GT]

Usually the adjustment is pretty small. What size throttle body do you have?

I think i have mine set to .6xxx for an 80mm tb. The other thing that usually needs to follow suite with the MAF is the ISC neutral drive functions FN875N.

When you had the IPSIBR down to .008 where was the ISC at that point.

[Cantedvalve]

Okay, EA suggests 1.63, but if I use 1.00, I get close to 0.00 on IPSIBR and 33% duty cycle on the ISC. My AFR ratio is pretty solid, but I have a really nasty fast hunt. Now, I know it isnt mechanical because I can fool with the settings and find a really nice idle. My spark is bouncing everywhere. Is spark the only place left for me to go at this point? Everything else seems "in spec."

BTW... I can set TB airflow to 1.63 and get a nice smooth idle... IPSIBR is .40 and ISC duty is 18, but I have a really nice idle... and no spark bounce. I KNOW this car can idle smooth and sweet... but I dont know what other issues I will cause if I let it idle smooth and sweet.

[86GT]

The default lower end of the ISC control is set to 17.5%, which is what you are seeing when you set the TB air flow that high. Basically what you are doing is taking the ISC out of the picture and locking it at 17.5.

To understand the idle tuning you have to know that the ISC is the first measure of idle control and then spark kicks in if the ISC can not maintain it. Think of the ISC as a coarse adjustment and the spark as a fine adjustment. In normal operations the spark should only bounce around 1 or 2 degrees to maintain a perfect idle. The ISC is slower in reaction time so it is used for dashpot control which is what brings your RPM down to idle setpoint slower. The act of slowly returning the RPM to idle does two things. It allows better emissions and it also does not allow the engine to stall.

With radical cams the fine adjustment of spark control sometimes it to much. I think the idle control of spark can swing from 0 -30 degrees to try and maintain idle. In a rough cam situation this is way to much. I dont have BE open right now to look up the function name but you can reduce this so that the EEC can not over compensate.

In the engineering terms, this is called over dampening or oscillation run away.

[Cantedvalve]

Ahhh... I have a modest cam (290/300 duration at full, 224/234 at .050, falt hydraulic), but I know what it can do at idle. Spark doesnt jump around at all if you take the ISC out of the equation... something that probably has other implications down the road.

I will look for that function to limit spark jumping. That is probably what I am needing. I have tried to just lower idle spark, and instead of jumping 16-30, now it jumps 10-20 or 8-16 I think the only reason the idle gets better is because I have limited how much the spark can move. I just got done datalogging my ISC flow at 10% increments, so I will incorporate that as well. After I posted, I got to thinking that it is the only "unknown" part of the equation. Cant hurt... although the engine got a little toasty :)

[86GT]

What matter is the cam overlap. The larger it is the more it mess with idle.

Take the idle setpoint and raise it 100rpm and then set the TB air flow back to something like .6 and see if the idle smooths out. Even in the old carberator days the best way to set idle was with a vacuum guage. The RPM and AFR that gave the highest vacuum was the sweat spot for the idle.

[roh92cp]

Usually the adjustment is pretty small. What size throttle body do you have?

I think i have mine set to .6xxx for an 80mm tb. The other thing that usually needs to follow suite with the MAF is the ISC neutral drive functions FN875N.

When you had the IPSIBR down to .008 where was the ISC at that point.

I have a 90mm T/B and I have raised the nuetral idle air look below. My ISCDC at .008 IPSIBR was 36%.

My FN875N settings
4080 1.99
1952 1.95
672 1.35
0 0.00
0 0.00
0 0.00

[roh92cp]

Anymore idea's on my idle stalling issue. I have not made any progress on it. At present I have to tap the peddle lightly once as the rpms fall below 1000 rpm to keep it from stalling. Its touchy if I tap it to hard it will spike up again and stall if I do it just right is settles into a good idle. I still have -0.400 IPSIBR on my logs can't seems to find what causing this.

[Cougar5.0]

Here's what I'm going to do. I'm going to post all of my tune related to idle highlighting where it's different from stock A9L and why I changed them.

Besides the below, I of course adjusted the throttle stop screw so that the ISC duty cycle would be 35 - 40% at idle.

Idle Scalars:
- idle upped to 768 RPM - IDLRPM & ISCLPD upped to match higher idle
- TKDTM & BZZRPM upped to allow longer higher RPM warm-up
- throttle body airflow (ITBMA) upped based on EA calculation
- DASMIN upped to prevent declutch stalling after WOT run
- DASPTO - from GUFx document "Insures at least some dashpot airflow on rapid tip-in/tip-outs. ..Typical value - 0.10 lbs/min"


ISC Idle Adder vs ACT:
- changed due to car idling up when blower was hot


ISC Idle Adder vs ECT:
- changed due to 160F thermostat - lower ECT did not let idle down all the way until adjusting this function



ISC Idle Adder vs RPM:
- changed due to idle set ~100 RPM higher than stock


ISC Gain Multiplier vs RPM:
- changed to center ISC gain around idle set ~100 RPM higher than stock


ISC Neutral Idle Air
- adjusted using EA as a guide (to match 85mm TB)
- ISC Drive Idle Air also changed to match this function as idle would be different when in gear (using neutral switch in manual tranny)


Idle - Spark Mult vs Drive RPM Error
- changed to match Spark Mult vs Neutral RPM Error since I'm using neutral switch with manual tranny


ISC Startup RPM vs ECT
- this is what I changed to combat stalling at warm start-up

[qikgts]

Great post Cougar.

Stuff like that makes this site friggin' awesome!!!

[roh92cp]

Wow that is an excellent explanation, and thanks for the screen shots. This gives me something to sink my teeth into.

[roh92cp]

latest update, I have made some progress on my idle issues. Thanks to Clint he had me unplug the isc and spout and tune the lowest points of the maf curve at a very low idle. That helped a bit, but I also added 30% up to 5 seconds in the ISC startup airflow mult table again, this time it worked. The car now starts revs and holds idle at 950 rpm for a couple seconds then settles. I still have an issue mostly when cold or warming up of stalling whith clutch in or nuetral coasting to a stop. Its happens under very light decel. Cougar Ive tried your adjustments and thanks you for all that tuning information. I'm not sure if it has helped though.

Is there something else I can do with this coasting and stalling issue in nuetral ot clutch engadge.