C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

1990 L98 stalling problem

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Old Jul 26, 2017 | 09:10 PM
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Default 1990 L98 stalling problem

Hello everyone,
i just rebuilt the bottom end ( new pistons, crank, camshaft, bearings etc
-bored .030 oversize
-stock heads with new valve job
-camshaft from comp cams (set up at 0 degrees)
-gross lift .480
- duration@ .050 Intake 210degrees exhaust 220degrees
-all the sensors and gaskets are brand new
-brand new fuel pump and adjustable fuel regulator set to 45psi
-no vacuum leaks
-new spark plugs and wires with new coil
-ignition based time at 11 degrees advanced
-automatic transmission 700r4
- both pre converters removed along with main converter
-AIR system removed/blocked
- no speedometer or odometer

The car is stalling on me when i come to a stop or coasting to a stop
(did not stall on me before engine rebuilt). Does not have the power and acceleration i was hoping for. it also hesitates to accelerate.

Any help is much appreciated,
Danny C

Last edited by Drautotech; Jul 26, 2017 at 09:13 PM.
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Old Jul 26, 2017 | 11:04 PM
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Although you bought a new fuel pump, have you measured the pressure from the Shrader valve? It sounds to me like yo have fuel pressure problems
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Old Jul 27, 2017 | 09:16 AM
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11 deg advanced is high IMO

what's your IAC counts?

Did you get it tuned?

How did you set base idle?
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Old Jul 27, 2017 | 09:31 AM
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Why no speedometer ???? Your PCM/ECM uses the VSS to prevent stall at stop !!!
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Old Jul 27, 2017 | 07:40 PM
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spoke the to comp cams today and they told me i should get the engine tuned to the new cam which means putting a hyper chip in it.
fuel pressure is at 45 psi and jumps up to 52psi with vacuum hose off
not sure about the iac counts i don't have a scan tool with me
should be 52 counts at idle i believe
speedometer and odometer has never worked since i had the car.
show 0mph and last known mileage
(i was told it could be the ccm)

Last edited by Drautotech; Jul 27, 2017 at 07:42 PM.
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Old Jul 27, 2017 | 07:42 PM
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Originally Posted by Deepa
11 deg advanced is high IMO

what's your IAC counts?

Did you get it tuned?

How did you set base idle?
how would you set base idle? isn't it computer controlled?
do you mean base timing?
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Old Jul 27, 2017 | 07:45 PM
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Originally Posted by Deepa
11 deg advanced is high IMO

what's your IAC counts?

Did you get it tuned?

How did you set base idle?
stock timing should at 6 degrees advanced. correct?
if we bring it down it will bring the idle down and might cause it to stall more IMO
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Old Jul 28, 2017 | 07:38 AM
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Originally Posted by Drautotech
spoke the to comp cams today and they told me i should get the engine tuned to the new cam which means putting a hyper chip in it.
fuel pressure is at 45 psi and jumps up to 52psi with vacuum hose off
not sure about the iac counts i don't have a scan tool with me
should be 52 counts at idle i believe
speedometer and odometer has never worked since i had the car.
show 0mph and last known mileage
(i was told it could be the ccm)
You might need to take it to a facility for a dyno tune. HyperJUNK won't work for squat.
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Old Jul 28, 2017 | 08:00 AM
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..... Set the base timing @ 6* ... There is a procedure in the factory service manual for setting the Minimum idle (base idle) ... make sure you reset the TPS if any changes are made to the idle speed adjusting screw ... with a scanner , you can set the idle by adjusting the IAC counts to the 20 range at hot idle in neutral ... again , recheck the TPS ..... ANY and ALL tuning advice is made while assuming that there are no other issues ... mechanical or otherwise ... with your set-up .....

Last edited by C409; Jul 28, 2017 at 08:03 AM.
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Old Jul 28, 2017 | 08:08 AM
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Fix the speedometer and the problem will go away - I promise !!!!
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