PeteSS
Junior Member
- Joined
- Oct 25, 2022
- Posts
- 1
- Reaction score
- 4
- Location
- Hendersonville
- First Name
- Pete
- Truck Year
- 1990
- Truck Model
- Suburban
- Engine Size
- 5.7
I have a 1990 v2500 suburban and had been trying to figure out what was causing my stall/hesitation from a idle. I'm more so posting this for anyone trying to diagnose hesitation or stalling from idle for search engine results. I fired the parts cannon in a way but it's interesting how much the gm tbi can compensate. I noticed the the hesitation appeared more during hotter weather, but eventually started happening more with colder weather but the engine had to be warmed up. Also noticed it happened more after replacing thermostat for proper temp one. Using laptop and aldl with tuner pro only suspect sign was INT sometimes dipping, o2 sensor voltage would go lean during hesitation, blm would climb at idle after few minutes
1. Replaced the distributor- found cracked magnet in 3 different places. Did not fix issue, ran probably the same.
2. Rebuilt the tbi and base gasket- didn't fix
3. Intake manifold gasket- found massive leak from oil gallery into intake which fixed a oil consumption problem- did not fix hesitation.
4. Did engine temp sensor and connection which had corrosion. -no improvement
5. Checked fuel pressure was at 11. Didn't have the ability check it under load, my rational was I was better off replacing the pump for the same cost as the fuel pump. Dropped tank, fuel pump was replaced with a delphi one but the rubber hose was ballooning, also a plastic hose clamp was used for the top and regular hose clamp on the bottom. My guess is the plastic clamp and hose failing would let gas flow past it when under no load due to back pressure increased, under a constant load the lack of back pressure would let flow normally. It would be worse when warm probably due the fuel being hotter swelling the rubber more. My INT and BLM were normal under anything above idle or tip in, even on the highway it wouldn't go lean. If I had to guess with a remote fuel gauge it would look normal but dip during the random hesitation. I replaced it with the later 454 fuel pump and this fixed the issue, but it was mainly the hose and clamps.
If anyone has questions let me know
1. Replaced the distributor- found cracked magnet in 3 different places. Did not fix issue, ran probably the same.
2. Rebuilt the tbi and base gasket- didn't fix
3. Intake manifold gasket- found massive leak from oil gallery into intake which fixed a oil consumption problem- did not fix hesitation.
4. Did engine temp sensor and connection which had corrosion. -no improvement
5. Checked fuel pressure was at 11. Didn't have the ability check it under load, my rational was I was better off replacing the pump for the same cost as the fuel pump. Dropped tank, fuel pump was replaced with a delphi one but the rubber hose was ballooning, also a plastic hose clamp was used for the top and regular hose clamp on the bottom. My guess is the plastic clamp and hose failing would let gas flow past it when under no load due to back pressure increased, under a constant load the lack of back pressure would let flow normally. It would be worse when warm probably due the fuel being hotter swelling the rubber more. My INT and BLM were normal under anything above idle or tip in, even on the highway it wouldn't go lean. If I had to guess with a remote fuel gauge it would look normal but dip during the random hesitation. I replaced it with the later 454 fuel pump and this fixed the issue, but it was mainly the hose and clamps.
If anyone has questions let me know
