94 GT HCI Build won't hold/find idle after warm to temp

[302hobronco]

In my 94 gt, I'm running a simular cam 224int 234exh @.050, 112 lobe sep .533 lift in my H/C/I 331. I have a bama chip in it. I'm constatly fighting idle issues. Coming to a stop it will high idle (1300rpm) until I come to a complete stop, than will drop down to 850rpm... or stall. On start up it surges for a minute before settling.
I have one of those plates that go between the iac and the throttle body that has adjustments to help with the idle instability. I need to install it and try it out.

 

[ttocs]

I tried bama with my trickflow setup and the tune was all wrong.

 

[302hobronco]

When I 1st used bama they sent me a build sheet to fill out. They sent me a tune and it fixed the problems I was having with that set up. Low speed bucking. Idle surge and I gained top end hp.
After I did my 331 build I reached out to them again for another tune. But this time they only asked for my compression ratio. I asked why they didn't want to know what heads, intake or cam I was using. They told me anymore they can only make changes for compression. I'm using the tunes they sent and I made 368hp and 398tq at the rear wheels. But the low speed bucking and idle surge is back.
Overall I'm not complaining about bama. But I think a stand alone computer set up is in my future.
The stock computer can handle only so much engine mods before it needs an in depth custom tune or to be replaced.
Ever thought about back tuning it to run on an A9L computer??

 

[RAU03MACH]

I have the bama on my 95 gt right now
But do plan on the megasquirt swap

 

[Tturaider]

So I have fixed my leaking injector by resetting them and tightening the fuel rail. Idle issue at warm start still there.

I have narrowed it to heat that has to be messing with one of the sensors. The engine bay gets REALLY hot, like so hot you can't touch the TFI.

I replaced the TFI with new Motorcraft, and installed a different distributor in case it was Pip sensor. Still no change.

To recap when cold the car starts, finds idle quickly (1k parked, 900 in drive AODE).. Once to temperature, if I turn it off and go to restart it it surges to 2k, bounces to 1.5k then falls through the floor to stall. If I let it sit to cool off, no issue.

Only trick I have found is to feather the throttle right before it bottoms out for about 5 times before it usually catches itself and finds the idle.

I keep going to back to the tune from Ted Jenkins in the event its a open/closed loop issue. He tells me there is nothing he can do.

Really at a loss.

 

[RAU03MACH]

So I have fixed my leaking injector by resetting them and tightening the fuel rail. Idle issue at warm start still there.

I have narrowed it to heat that has to be messing with one of the sensors. The engine bay gets REALLY hot, like so hot you can't touch the TFI.

I replaced the TFI with new Motorcraft, and installed a different distributor in case it was Pip sensor. Still no change.

To recap when cold the car starts, finds idle quickly (1k parked, 900 in drive AODE).. Once to temperature, if I turn it off and go to restart it it surges to 2k, bounces to 1.5k then falls through the floor to stall. If I let it sit to cool off, no issue.

Only trick I have found is to feather the throttle right before it bottoms out for about 5 times before it usually catches itself and finds the idle.

I keep going to back to the tune from Ted Jenkins in the event its a open/closed loop issue. He tells me there is nothing he can do.

Really at a loss.

Just wondering have you tried adjusting the screw on top of the throttle body to ajust air
Mark that screw were its at
Turn screw clock wise in in small turns till it quits trying to die on you
If it dose not work always return to mark it was at

On mine it wants to be all the way out just about
Where the screw is flush with the body


It may need to be adjusted in or out

 

[ttocs]

I have to agree with ted that it probably is not in the tune and something on the motor. If you think it is temp related, by chance are any of the sensors harnesses missing clips that hold them together? If so replace them and the next time it is doing this go under the hood and try to grab/pull/tug on any wire harness/connection you can find to see if the motor makes any changes when you do it. Also have we smoke tested the intake for leaks or just doing a visual inspection?

 

[Tturaider]

Just wondering have you tried adjusting the screw on top of the throttle body to ajust air
Mark that screw were its at
Turn screw clock wise in in small turns till it quits trying to die on you
If it dose not work always return to mark it was at

On mine it wants to be all the way out just about
Where the screw is flush with the body


It may need to be adjusted in or out

The small threaded (bleeder) screw was reset with the feeler gauge per BBK instruction and then only backed about 1 full turn clockwise.

Then used the idle screw (larger one toward driver side) has been adjusted to achieve consistent idle.

Again no issue of idle in neutral or gear & driving when the motor is cold started. Only an issue when started at temp. Which makes me think it is a sensor or computer issue (closed loop vs open loop) contributed by heat.

 

[Wmac]

What's the AFR at hot start-up? Sure sounds like it's way lean.

After it stalls, does it start up and idle?

 

[Tturaider]

What's the AFR at hot start-up? Sure sounds like it's way lean.

After it stalls, does it start up and idle?

I dont have a gauge so cant measure the AFR.

At hot start up - it acts the same everytime. It will crank, fire (but not as sudden as cold start), RPMs bounce to 2k, down to 1.5k. Then instead of falling into idle at around 1k (park on AODE), it just falls out and stalls. Sometimes it will try to find itself at 500rpm but cant quite catch itself.

If i give it a little throttle before it chokes out at 500, it will repeat the same behavior pattern above. If I do it 5-6 times though, it will usually find itself and hold idle in park.

I have noticed though once I shift into drive or reverse it sometimes stalls instantly which I dont understand. I have the start the whole process over again or just let it sit for 10 mins.

However, if I do get it into D/R without stalling (after hot start), it drives great and idles consistent at stop signs/lights etc.

 

[RAU03MACH]

To me it sounds like it's vapor locking
If it is hard starting at hot Temps
Fuel will evaporate in hot fuel lines

What is the psi on fuel line when starting hot temp

 

[Wmac]

Don't know whether you have spent any time reading over at efidynotuning, but decipha describes a very similar condition on cold start as cold idle enrichment. BUT, your issue is a hot idle restart.
I would be tempting to through a # or 2 of fuel at it, if you have an adjustable fuel pressure regulator, just to see if that had an effect.
And do a smoke test.
If you have the stock t/b, maybe try it. I had a bbk 70mm (bot used) and it was a big pain in the ass. Lucked into a Ford 65mm and it has made a big difference in idle, but still have have similar issues as yours on cold start. Goes very lean for a minute or 2.

 

[Tturaider]

Long overdue follow up but last summer I just put the EGR back on and bam. No issue.

I have no idea why that was the solve but it was. Also no more CIL which is a bonus.