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

Tturaider · Jun 10, 2023

Hi Guys.

94 GT Vert here. Car ran great with 100% stock set up.

Build

HCI Trick Flow Top End with Stage 1 Cam, 170 TW Heads, Street Burner Intake,
BBK shorties
Flow Tech 94/95 OR H pipe
Magnaflow cat back.
Precision Stall 2800-3000 installed on the AODE.
Ted Jenkins @ Tuning Innovations tune with SCT Chip.

The issue I am having is the car with start, find idle in park and all gears, drive great up until the point I turn it off. Once I go to restart it, it will start and idle will bounce to 2k and maybe hunt for a few seconds before stalling. Sometimes I have gotten luckly to feather the gas for 20-30 secs around 2k rpm and it finds itself to idle.

It ONLY happens when warm. Once I let it sit for 30 mins it then fires back up and finds idle just fine.

Here is what is different on this build besides above.

Emissions (EGR) delete
Trans Go Shift Kit
3.73 gears
MSD distributor (replaced Remanuf)
ProM MAF 75mm 24#
24# injectors
255 Fuel pump
New alternator
New Battery

Here is what I have done:

Updated Chip to accommodate High stall converter increasing idle
Base Idle Reset (in gear parked idles 850-950 consistently, In park right at hair under 1k.
Replaced ECT Sensor
Replaced IAC Sensor
TPS checked in range of 1.0
Ran codes with only ones popping relating the EGR

What could it be

I have read it could be IAT or other sensors but if car ran well before?
Maybe MAF is shitty but runs great all other times.
PIP sensor or Distrib? However runs well when cold started
TFI module? Read that it can get hot and malfunction during heatsoak

What do you guys think?

Wmac · Jun 10, 2023

Maybe try a smoke test before throwing anymore parts at it?

What does the tuner think the issue is?

Nice build btw, what rear gear are you running?

RAU03MACH · Jun 10, 2023

Unplug the computer try plugging back in
And to reset relearn unhook both battery terminal pos neg
Touch together for a few minutes to drain any power on computer
Hook star up

Also do a wiggle test on all harness to see if changes accure

Tturaider · Jun 11, 2023

Wmac said:
Maybe try a smoke test before throwing anymore parts at it?

What does the tuner think the issue is?

Nice build btw, what rear gear are you running?

3.73 gears. Shift Kit in the AODE along with the precision stall. Makes for a fun car around town.

Regarding smoke, if I had a vacuum issue wouldnt it be present all the time vs only when warm?

Ted the tuner not much help at all to be honest.

Tturaider · Jun 11, 2023

RAU03MACH said:
Unplug the computer try plugging back in
And to reset relearn unhook both battery terminal pos neg
Touch together for a few minutes to drain any power on computer
Hook star up

Also do a wiggle test on all harness to see if changes accure

you think its electrical?

RAU03MACH · Jun 11, 2023

Could be with vibration

Tturaider · Jun 11, 2023

RAU03MACH said:
Could be with vibration

But only after its warmed to temp?

RAU03MACH · Jun 11, 2023

Not sure
Gotta start somewhere
That's part of troubleshooting

RAU03MACH · Jun 11, 2023

I would also check timing and run a compression test check fuel psi as well
Just to make sure you are in spec

302hobronco · Jun 13, 2023

Does the cam pull enough vacuum for the computer to be happy? When cold it will be in closed loop and not care about the vacuum reading. Once warm it will go into open loop and start adjusting engine parameters for optimum running. The 94/95 computers are very sensitive when it comes to mods. Just my 2 cents from my experience.

RAU03MACH · Jun 13, 2023

He may be running a stalk cam
With that there should not be a problem
Definitely got to check some things over

Wmac · Jun 13, 2023

Nothing "stalk" on the OP's build; well maybe the short block.

Agree with post #8.

Tturaider · Jun 13, 2023

RAU03MACH said:
He may be running a stalk cam
With that there should not be a problem
Definitely got to check some things over

TF Stage One cam...

RAU03MACH · Jun 13, 2023

Tturaider said:
TF Stage One cam...

any thing done to the heads

Tturaider · Jun 14, 2023

RAU03MACH said:
any thing done to the heads

Brand New TW 170s, 1.6 RR

RAU03MACH · Jun 14, 2023

I would run a few test on it
To to see if any thing changes
That type of stuff hard to trouble make sure everything is bolted down and sealed properly
Like i say gotta start somwhere

71cobra · Jun 14, 2023

Tturaider said:
Hi Guys.

94 GT Vert here. Car ran great with 100% stock set up.

Build

HCI Trick Flow Top End with Stage 1 Cam, 170 TW Heads, Street Burner Intake,

BBK shorties

Flow Tech 94/95 OR H pipe

Magnaflow cat back.

Precision Stall 2800-3000 installed on the AODE.

Ted Jenkins @ Tuning Innovations tune with SCT Chip.

The issue I am having is the car with start, find idle in park and all gears, drive great up until the point I turn it off. Once I go to restart it, it will start and idle will bounce to 2k and maybe hunt for a few seconds before stalling. Sometimes I have gotten luckly to feather the gas for 20-30 secs around 2k rpm and it finds itself to idle.

It ONLY happens when warm. Once I let it sit for 30 mins it then fires back up and finds idle just fine.

Here is what is different on this build besides above.

Emissions (EGR) delete

Trans Go Shift Kit

3.73 gears

MSD distributor (replaced Remanuf)

ProM MAF 75mm 24#

24# injectors

255 Fuel pump

New alternator

New Battery

Here is what I have done:

Updated Chip to accommodate High stall converter increasing idle

Base Idle Reset (in gear parked idles 850-950 consistently, In park right at hair under 1k.

Replaced ECT Sensor

Replaced IAC Sensor

TPS checked in range of 1.0

Ran codes with only ones popping relating the EGR

What could it be

I have read it could be IAT or other sensors but if car ran well before?

Maybe MAF is shitty but runs great all other times.

PIP sensor or Distrib? However runs well when cold started

TFI module? Read that it can get hot and malfunction during heatsoak

What do you guys think?

I had a similar problem with a similar build. Tried everything. It would run ok except when cold the idle would go down too far and it would turn off. When it warmed up it would not have that issue except when i turned it off for a few minutes it would start but would not idle until until it ran for a few minutes. It seems that the engine heat soaked when I turned it off after running a while and some electronics were acting up until the underhood temp went down.
My solution was to to replace the TPS with a new one. Suddenly, the problem disappeared and its been fine ever since about 3 years go.
Thats my story. I'm not saying 'that this is your solution but I had checked the voltage and it was fine when it was cold and it was in range. Neer checked it when hot because t would cool off quickly.

Tturaider · Jun 14, 2023

I did notice today when fired up the injector nearest front on passenger side had white smoke escaping and building up moisture on that injector body. I had noticed a raw fuel smell and assume this has to be it. Upon looking closer there is fuel leaking down from the fuel rail where the injector connects.

(The injectors i installed where passed to be in the purchase of my manifold by the seller, so definitely used)

This might be my issue that I need to fix.