Originally Posted by mickey_bigdaddy

****PLEASE DO NOT HIJACK THIS THREAD*****

Hello, I'm new to this forum but want to contribute with my problem scenario which I cannot find a solution. I have found this very same problem numerous times on this and other forums. But as in every other post, I see a bunch of suggestions, continuous part change outs and finally an open ended unanswered problem that still exists. If someone knows the answer, then point it out immediately. If you have comments or suggestions, please add value. But, by no means, DO NOT HIJACK THIS THREAD WITH YOUR OWN PROBLEM. I want to solve this problem once and for all and see if this thread will be useful to someone else in the future. I will edit this first post as I fine tune this issue and the tests that I do so be aware in advance.

My vehicle:
1999 LS Blazer, 4.3L, Vin W, 2WD, 4 Door, Automatic, 125,000 miles.

My problem scenarios:
1. After engine is warmed up pretty well at least 30-60 minutes, Blazer has intermittent stalling and eventually dies. There are no error codes.
2. This is a gradual problem that is first noticed with a lack of power that builds up.
3. As the gas pedal is applied further, the vehicle tends to lose more power and ultimately just dies.
4. At restart, the vehicle can go about 300 feet and the cycle happens again.
5. At restart, if it is left in PARK, the vehicle just sits there idling fine but eventually sputters and dies.
6. This tends to occur when it is hot outside. Let's say over 95-100 degrees.
7. After the engine is allowed to cool off, it can be driven again for a good 30-60 minutes and then it happens all over again.
8. When this situation is happening and the motor is still running, the oil pressure gauge is hovering around 30 psi, Otherwise, it is up around 40-45 psi.
9. Engine temp is around 195 degrees, never goes above that.
10. Coolant level is full and does not leak.
11. One time on a long trip after a fill up, I did smell gas fumes for a little. I had just filled up so this may be what I was smelling. Not sure.
12. Also, notice a "sweet" smell coming from exhaust. I have this same smell from my Ford F150 so when I smelled it from the Blazer it caught my attention.
13. I hear an intermittent purring, it's hard to describe. It sounds like a heat shield light vibration. Kinda like the way a brake rotor dust shield sounds when its loose. This is not something that is continuous and it seems to be coming from the fuel tank area, left rear side of vehicle. Exhaust is on the right side.

Points to mention:
1. This motor is a swap into my Blazer since the original one had broken a rod from coolant leak. I bought it that way and I did the engine swap.
2. All the following are new parts from the swap:
- Intake upper & lower, manifold gaskets.
- Coolant, green. Why, because I don't like doing intake gasket repairs and I hate changing engines. Research this and you'll know why.
- Positive Crankcase Vent. Valve (PCV)
- Ignition Control Module (ICM), because I wanted new
- Ignition Coil, because I wanted new
- Mass Airflow (MAF) Sensor, because I wanted new
- Oil Pressure Sensor, because engine was out and it's a pain to change
- Oil Pump, because engine was out and it's a pain to change
- Knock Sensor, because engine was out and it's a pain to change
- Coolant Temp Sensor, because engine was out and it's a pain to change
- Distributor, cap, rotor, wires, plugs
- 195 degree thermostat
- Battery
- Air filter
- Fuel filter
- Fuel Pump Relay, OEM GM part
- Gas Tank Cap, OEM GM part
- 10-30W Oil
3. MOD: Throttle body mod, removed diffuser/restrictor off bottom of blade

Tests that I have done so far:
1. Drove vehicle on highway/city at night for 60 minutes at 85 degrees outside and the problem does not occur.

2. Fuel pressure tests:
Fuel Test #1: Engine cold, conditions at 7 pm, 85 degrees outside temp, gas tank 1/2 full, no rain:
- 65 psi at ignition on, engine off, fuel pump primes
- 58 psi at start up and idle
- 65 psi at accelerate
Fuel Test #2: Engine cold, first start of the day, conditions at 12 pm noon, 88 degrees outside temp, gas tank 1/2 full. no rain:
- 65 psi at ignition on, engine off, fuel pump primes
- 58 psi at start up and idle
- 65 psi at accelerate
This happens for all tests upon engine turn off:
- Pressure goes back to 65 psi as fuel pump runs for 2 seconds.
- When pump shuts off, fuel pressure comes back down to 58 psi, holds for a few seconds.
- In the next 15 seconds, pressure goes back to 65 psi
- Pressure is 60 psi after 10 min
- Pressure is 60 psi after 20 min
- Pressure is 58 psi after 30 min

3. Oil pressure test:
- Can't remember the number but it was in spec.
4. Fuel injector connector test with noid light and all signals were there.
5. Fuel injector fuel test, all injectors were squirting fuel out.
6. Engine compression test, all cylinders check to be 130-134 psi.
7. Catalytic converter pressure test done by muffler shop, before and after cat and muffler, no high pressure buildup. They check good.

Tests to do:
1. Fuel pressure test in heat of day
2. Fuel pressure regulator
3. MAF
4. Vacuum leak around air intake
5. EVAP system
6. TPS
7. EGR
8. Gas tank pressure vent clogging or fuel return line clogging
9. ICM
10. Whatever it takes to fix this permanently!


Keyword phrases:
blazer stumbles sputters when accelerator pushed hard, no error codes, stalls on hills, fuel pump whines when hot, stalls when hot outside, fuel pump making loud howling noise, buzzing noise under car, clogged cats catalytic converter, fuel pressure regulator, fuel pump pressure test, sweet smell from exhaust, charcoal canister, evap canister, ICM overheat