Unable to figure out issue - Negative STFT

[acemastr]

I need the collective expertise here!

Background:
55k miles, had a Roush blower and chiller on since 50k. Wengerd tuned on 93.

Since the chiller I've had hot start issues, the revs will drop to 300-400 and then come back a couple of seconds later, it then throws a P0430 every time (this only happens when hot starting, does not appear when driving). I was also experiencing issues at a light where the same thing would happen. When this happens the STFT will go to -25, fuel pressure remains the same on high and low.

I thought it may be purge valve so I swapped out the entire valve, no difference. I then disconnected the purge valve from the intake and plugged it, no difference.
I have now just changed the VCT solenoids which seems to have resolved the stop light idle issue but the hot start remains. I'm also now having an issue with partial positive throttle causing the STFT to drop to -10 and the car shudders, if I get out of it and back in it generally resolves it.

Where do I go next? What could be causing the STFT to pull so much fuel out that the engine almost stalls?

Appreciate any help!

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[SnowFox]

You checked for Vaccum leaks?

 

[Kryptickzz]

Could it be bad O2s?

 

[acemastr]

You checked for Vaccum leaks?

Negative on the vacuum leak, I sprayed brake clean all over and nothing happened. Removing the evap stopper-plug from the blower causes an increase in idle so it should be noticeable.

It idles better since the VCT solenoids but the part throttle negative STFT and hot start are still present. When it happens it happens on both banks, does the ECU treat each bank separately when it comes to O2 sensors? or does it average them and adjust accordingly?

 

[Kryptickzz]

One bad bank could cause issues

 

[Exploded_Muffin]

I need the collective expertise here!

Background:
55k miles, had a Roush blower and chiller on since 50k. Wengerd tuned on 93.

Since the chiller I've had hot start issues, the revs will drop to 300-400 and then come back a couple of seconds later, it then throws a P0430 every time (this only happens when hot starting, does not appear when driving). I was also experiencing issues at a light where the same thing would happen. When this happens the STFT will go to -25, fuel pressure remains the same on high and low.

I thought it may be purge valve so I swapped out the entire valve, no difference. I then disconnected the purge valve from the intake and plugged it, no difference.
I have now just changed the VCT solenoids which seems to have resolved the stop light idle issue but the hot start remains. I'm also now having an issue with partial positive throttle causing the STFT to drop to -10 and the car shudders, if I get out of it and back in it generally resolves it.

Where do I go next? What could be causing the STFT to pull so much fuel out that the engine almost stalls?

Appreciate any help!

You're likely having some condensation pooling up in your intake/blower especially as you're in a very humid location running a chiller setup.
Read through this:
https://www.ram-trx.com/threads/cons-of-interchiller-in-humid-environments.18038/

Run with your AC/Chiller off for a while and see if it improves.
If it does that confirms it's your chiller setup and then you have a few choices - work with your tuner to tweak your warm start fueling, improvise a condensate drain setup, remove the chiller setup, or relocate.

Sounds similar to the issue I and a few others had with methanol kits as well:
https://www.mustang6g.com/forums/threads/suddenly-stalling-on-warm-hot-starts.177583/

 

[acemastr]

You're likely having some condensation pooling up in your intake/blower especially as you're in a very humid location running a chiller setup.
Read through this:
https://www.ram-trx.com/threads/cons-of-interchiller-in-humid-environments.18038/

Run with your AC/Chiller off for a while and see if it improves.
If it does that confirms it's your chiller setup and then you have a few choices - work with your tuner to tweak your warm start fueling, improvise a condensate drain setup, remove the chiller setup, or relocate.

Sounds similar to the issue I and a few others had with methanol kits as well:
https://www.mustang6g.com/forums/threads/suddenly-stalling-on-warm-hot-starts.177583/

You know... you might be on to something, this hadn't crossed my mind at all but it did all start when the chiller went on.

It may not be the answer to the shudder and -10 STFT when slowly accelerating (sometimes, not every time)

 

[acemastr]

So, still juddering even after a trans fluid change.

It's perfect when WOT, shifts fairly fine (it's a 10R80, it'll never be perfect), but 20-40% throttle it'll judder as it accelerates.

Surely I can't have killed a transmission in 60k miles? (5k supercharged) I always heat it up before getting on it.

Anyone have any ideas? I'm running out of them!

 

[wingnutt]

The shuddering sounds like a torque converter, not necessarily the whole trans…

back in the good ol days, we would wire a switch to lock it out but I dunno if that’s been done to the A10s?

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