FAST, dies going in gear

[Jackson]

With help of an experienced tuner, got idle and cranking sorted out. However, when car is idling and shifted into gear (reverse or drive) it dies.

In this case the IAC opens up to 180 from a defined value of 51, RPM drops from idle of 900 to just above 500 and it starts hunting in that range. For the most part AF is on target ...

We looked over all of the tables and found no significant mis-configurations. We also tried adding and removing values in desired AFR to affect enrichment.

Couple of ideas ...

1) At this point is desired AF ratio doing much? Thinking about it now I'm wondering if its getting below the closed loop enable (500rpm).

2) The IAC motor does follow Throttle Follower values when revving at idle, except for when going into gear and the above scenario happens. The IAC is recently new and I'm not totally suspecting a bad part yet. Giving the motor some RPM will allow it to every so often fin its way back to the defined thorttle follower value.

3) Classic case of VE adjustment? Put it in gear, let the RPM drop, IAC skyrocket, and see which VE cell it hits. Adjsut that cell either way + or - ?

4) Tried adjusting the throttle blades (open close) via the screw but there was no noticable change.

Thoughts?

 

[kidrick]

Take a look at my "Lean Stall In Gear" post. Maybe this will help you. You say that the A/F is close to target, so I would guess the VE target is OK too. You can also try raising the Idle Parameters to 30 and 20 and see if this works. Car may start to surge at idle so just back down the numbers a little. Good Luck.

 

[Reggie West]

A couple of suggestions.

1. Get the closed loop out of the picture and force values in the VE table. Having the closed loop set at 500 rpms will not help the idle, the best way I have found is to use the WB for rpm ranges above 2000 and up. The computer is doing what it can to keep the car running but it is a matter of tuning.

2. Keep the throttle blades closed all the way. Once you crack the throttle blades, the IAC will try to compensate by taking out air that all of a sudden has increased. Let the IAC do its job, if the graph is jumping around at idle then its working. The more erratic the IAC is, the more you need to get the VE table right at the corresponding cells. Get the VE tables right first and then you can add air if necessary in the IAC tables if necessary.

3. If you are trying to get the car to idle with an A/F ratio of 14.7 to 1 and its not working, give it some more fuel. The GN required an A/F ratio of 12.5 to 1 to idle correctly but its nice and smooth now. I did not think the motor needed that much fuel at idle, especially with 83 lb/hr injectors.

4. When tuning on the Ve table, get the car to idle use whatever values you have to do it. Once that is done you can slowly figure out what is best for idle. Smooth transitions between cells will make the car accelerate nicely. For instance, a jump between cells that have values of 22 and 40 can be too much fuel for the motor. So if you change the values to 22 and 32 for instance, the motor will be much smoother.

Hope this helps

 

[Syclone Dude]

I had a similar problem on my syclone with the FAST, with Harry's (PTE) help (and a call on the red phone to Craig Smith at FAST) we decided that it just wasn't gonna idle in closed loop (just as reggie west said) actually my truck likes to idle at high 12's low13's, another thing to try is open the trottle plates so the IAC motors is used as little as possible so when it starts to die on ya it has plenty of throttle to open.

HTH
BigAl...

 

[Ricky Trussell]

Originally posted by Reggie West

2. Keep the throttle blades closed all the way. Once you crack the throttle blades, the IAC will try to compensate by taking out air that all of a sudden has increased. Let the IAC do its job, if the graph is jumping around at idle then its working. The more erratic the IAC is, the more you need to get the VE table right at the corresponding cells. Get the VE tables right first and then you can add air if necessary in the IAC tables if necessary.


Hope this helps

Not trying to jack the thread but..... would you explain why you want the throttle blades closed all the way at idle? This is against all I have been told when tuning the FAST system. Not saying you are wrong but I would like your point of view.

 

[Jackson]

Another item to know about this specific problem ... opening and closing of TB blades aside ...

The problem is when idling and moving it into gear it wants to stall/die.

However ...

When unplugging the IAC and shifting it into gear, it hold RPM fine. It does hunt a little because there is no IAC to adjust.

Otherwise with it plugged in, the IAC simply shoort to max opening and the ECU doesn't want to recover, no matter which way I swing fueling though VE or target AFR ....

Something with D gain and P gain?

 

[Syclone Dude]

What is your d and p gain set at?

BigAl...

 

[Jackson]

Originally posted by Syclone Dude
What is your d and p gain set at?

BigAl...

P Gain = 38

D Gain = 5

Max TPS for Idle [%] =18

I just double checked, when I unplug the IAC completely and shift into gear, the RPM drops from 1000 to 900 and holds steady. Overall with it unplugged, RPM hunts and pecks a little for position, though does not die (far from it) going into gear. I'd make the assumption that VE is reasonable.

This tranny is a COAN TH400 full reverse manual with transbrake. No TV cable or anything rlectrically realted to it.

The harness I'm using is a PNP setup from whiteracing.

Thoughts?

 

[norbs]

Set the D gain to about 14 and the p gain to 30, see if this help?

 

[Reggie West]

Not trying to jack the thread but..... would you explain why you want the throttle blades closed all the way at idle? This is against all I have been told when tuning the FAST system. Not saying you are wrong but I would like your point of view.

I tried to get the motor to idle by cracking the throttle blades, it did not help. I had vacuum leaks I was chasing too but that is what worked for me. Once I had the throttle blades closed, the IAC counts come back down to reality and it fluctuated a little bit but then and only then would the motor idle correctly.

With the blades closed I could go in to the IAC menu and increase or decrease the counts.

 

[bobc455]

>I tried to get the motor to idle by cracking the throttle blades, it did not help. I had vacuum leaks I was chasing too but that is what worked for me. Once I had the throttle blades closed, the IAC counts come back down to reality and it fluctuated a little bit but then and only then would the motor idle correctly.

Closing the throttle blades should increase the IAC position, not decrease it (unless you are wired backwards).

>With the blades closed I could go in to the IAC menu and increase or decrease the counts.

Nothing in the menus will let you change IAC position, unless you are talking about starting. For idle, the IAC action is automatic.

I still preach that throttle blades should be letting the car idle, the IAC should really only be active during warmup and maybe go up to 12-15 when you drop into gear. Just my opinion.

-Bob Cunningham

 

[Ricky Trussell]

I agree with you Bob. My throttle follower is at 10 at idle, my throttle blades control my idle and I taper up my follower so the engine does not die on decel.

I have seen allot of followers set at like 30 at idle though.... I don't understand why.

 

[Jackson]

In part I'd say this has been resolved. Its not dying going into gear after the following.

1) Adding a lot of fuel via the VE table.

2) Adding a IAC bypass/bleed hole.

The following is a pic (bad and fuzzy) of the throttle body I'm using. If you lookin the lower center there is no bleed hole compared to the stock. The adjustment screw would only open the blades so much.

So far the result has been improved cranking but target idle in park (1400) is higher than in gear (900). Once in gear the RPM drops. Adding fuel via VE also helped a bit so thats probably the next target.


My TB before drilling hole ...
http://jon.shoberg.net/CarStuff/Pics/throttlebody/IM000464.JPG/variant/medium

Some photo of stock TB showing bleed hole ...
http://www.hashmarks.com/techtips/throttle_body_mod/06-stock_throttle_body-500.jpg


Dumb video of car at idle ... while working on idle ...
http://tmp.shoberg.net/idle.mpg

 

[bobc455]

Is there a setscrew on that TB to hold the blades open further?

(I can't imagine a throttle body without adjustable idle setpoint)

If so, why did you opt to drill a hole instead of just open the throttle blades further?

-Bob Cunningham

 

[Jackson]

There is a set screw but the range of adjustment isn't significant. The hole was drilled in the exact stock location and to the same size.

Whereas yesterday the idle was a bit too high, its now too low. Time to seek some professional help

 

[Ricky Trussell]

Some questions that might seem stupid.
1)You are letting the engine warm up before adjusting right?
2)Are you sure you have the valves adjusted okay?
3)Is the IAC sticking for some reason?

Go back thru your setting to make sure something has not changed.

I have had my 800 rpm idle setting to change at the 184 degree mark and spike up to 2000rpm more than three time in the last few months. It has done this lately also. This makes the IAC open to try to get the idle speed.

 

[Jackson]

somewhat fixed ...

Ricky,
1) yes, car is holding between 170-180deg.
2) yes, valves are fine
3) no, this is a new IAC and it does open fine and get back on track ....


I used the adjustable screw to open the TB blades all the way as well as adding a stock sized IAC bleed hole to my aftermarket TB (Holley), as it did not have one.

When at temp the car wants to idle around 1000rpm which is ok for my setup. Beyond cranking and afterstart enrichment the IAC would open way up and revs would drop to around 500 rpm.

So far the solution has been to set the target idle to about 600 rpm which is lower than the 1000rpm idle in park and 800 rpm idle in drive. In setting it lower the IAC maintains the throttle follower settings at idle, a value of 10. I'm able to shift from park to reverse and drive without the car dying. Even getting the VE cells at idle setup was not much of a problem.

I fell this is more of a "hack" given that I doubt it will be able to maintain a higher idle (1400) when temps are colder (60-80 deg) versus normal run. We'll see....

 

[Ricky Trussell]

What about an update?

I listened to your video and was wondering if the engine was warm when your cranked it? I noticed you had to open the tb to get it to crank. Could it be you have too much fuel at cranking and at idle areas?

I had wondered about camshaft duration and converter but I noticed the air box so camshaft and converter should be no issue.

 

[Jackson]

Ricky,

All is well. I'm working though various cold start scenarios but for the most part things are going well. Thanks to everyone who reads and posts for the help.

-j