Excessive cranking to start, stalling on medium/hard throttle
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Teching In
Joined: Nov 2017
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Excessive cranking to start, stalling on medium/hard throttle Hello, hoping to get a few opinions on a long, ongoing issue I am having with my 94 Formula. Completely stock LT1 Auto ~110k. Having an issue (spanning throughout many years on and off) where the car will require excessive cranking for the car to start. Currently requiring upwards of nearly 30 seconds or more of cranking for a cold start. Once the car has started once, it takes about 2-3 seconds of cranking to start. Still excessive when comparing to my 94 Fleetwood with the same drivetrain but taking about 1 second or less to crank at any given time. The car will idle great and you can raise the RPMs slowly and no issues. When you try raising the RPMs more quickly, it stumbles really hard and in many cases just stops firing altogether and would stall if I don't close the throttle. No SES light or codes when using a scanner. The car is a garage queen.
Opti was the first to be replaced. It's a reman and granted not ACDelco brand, but it was having the same issue before I replaced it (on probably its 3rd Opti since owning it about 4-5 years now). I have tested for power, ground, and resistance on all harnesses (sensors, opti harness, icm/coil harness) and even AC voltage signaling the ICM/Coil to fire. I have swapped the ICM/Coil from my Fleetwood with no changes. I have swapped PCMs with and without flashing from the Fleetwood->FBody. We have swapped spark plugs and wires. I have tested for spark from the coil and at multiple plugs. I have tested for fuel pressure which primes and holds even while running, giving throttle, or disconnecting the vacuum line and it is all in spec. I even flashed out the VATS from the Fbody PCM. I have a Tech2 Scanner and can see the coolant temp, map, baro, maf, O2s, tps, low and high res, and everything else seems to be working correctly when comparing it to my Fleetwood. I have swapped maps, mafs, and nearly anything else swappable between the two cars. Fleetwood will run, but the Formula struggles.
I have gone through many posts across multiple forums and cannot find a solid solution. Any ideas or inputs are highly valued at this point. Thanks in advance.
Opti was the first to be replaced. It's a reman and granted not ACDelco brand, but it was having the same issue before I replaced it (on probably its 3rd Opti since owning it about 4-5 years now). I have tested for power, ground, and resistance on all harnesses (sensors, opti harness, icm/coil harness) and even AC voltage signaling the ICM/Coil to fire. I have swapped the ICM/Coil from my Fleetwood with no changes. I have swapped PCMs with and without flashing from the Fleetwood->FBody. We have swapped spark plugs and wires. I have tested for spark from the coil and at multiple plugs. I have tested for fuel pressure which primes and holds even while running, giving throttle, or disconnecting the vacuum line and it is all in spec. I even flashed out the VATS from the Fbody PCM. I have a Tech2 Scanner and can see the coolant temp, map, baro, maf, O2s, tps, low and high res, and everything else seems to be working correctly when comparing it to my Fleetwood. I have swapped maps, mafs, and nearly anything else swappable between the two cars. Fleetwood will run, but the Formula struggles.
I have gone through many posts across multiple forums and cannot find a solid solution. Any ideas or inputs are highly valued at this point. Thanks in advance.
