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

Tturaider

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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?
 
Last edited:

Wmac

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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

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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
 
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Tturaider

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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.
 
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Tturaider

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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

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

302hobronco

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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

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

RAU03MACH

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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

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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.
 
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Tturaider

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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.
 
Last edited:

ttocs

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I have the same heads/cam. I tried an email tune but it was never able to make it happy and I finally had to take it to a dyno to get it tuned.
 

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