5.7 wants to stall when stoped when HVAC is on

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SUBURBAN5

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Here’s another clue to the problem. CHECK GAUGES light comes on and oil pressure drops. See picture

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Man I have this problem ever since I got the rebuilt motor. Dummy mechanic blamed the guage. I swapped 2 sending units and new after market guage. All the same readings. Morning and first start, Had good pressure. Running a while, it would drop to low pressure. Finally just unplugged the guage and driven it sense. My guess is the pump or bearings . But gonna waiting til it gets worse. Before I deal with it. Really want a 383stroker lol
 

stutaeng

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Man I have this problem ever since I got the rebuilt motor. Dummy mechanic blamed the guage. I swapped 2 sending units and new after market guage. All the same readings. Morning and first start, Had good pressure. Running a while, it would drop to low pressure. Finally just unplugged the guage and driven it sense. My guess is the pump or bearings . But gonna waiting til it gets worse. Before I deal with it. Really want a 383stroker lol

Most likely bearings. But this started after a rebuild? Maybe clearance was too loose on the rebuild? Maybe they didn't check them?

You can try switching to heavier oil to gain a bit of pressure. I think I switched to like 20W-50 on my 4.3 and got me from like 5 psi to 8 psi. Checked with a mechanical guage.
It's
still running like that after 12 months. Getting finally ready to swap the engine.
 

SUBURBAN5

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Most likely bearings. But this started after a rebuild? Maybe clearance was too loose on the rebuild? Maybe they didn't check them?

You can try switching to heavier oil to gain a bit of pressure. I think I switched to like 20W-50 on my 4.3 and got me from like 5 psi to 8 psi. Checked with a mechanical guage.
It's
still running like that after 12 months. Getting finally ready to swap the engine.

That's what I figured. I've been putting 10w40
Scared to put thicker lol. But I agree. I need a mechanical guage for the real readings lol. Motor about 2 or 3 yrs old. Been running it like this for quit some time. Thanks for the suggestions
 

Schurkey

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It wants to stall when stopped (in Drive -foot on peddle) ONLY when HVAC is on and ONLY when the engine has warmed up. The RPM drops to 500 and oil pressure drops. RPM increases back to 750 when I put in PARK.
Lots of folks have suggested diagnosing for engine problems. There's about thirty things that could cause your symptoms.

One thing that hasn't been mentioned is verifying the A/C refrigerant "high side" pressure. If the compressor is pushing 300+ psi, it's going to be a huge drag on the engine; more than the engine can drive at idle.
 
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