Engine dies when downshifting uphill

[SwitchSkier]

My car has sometimes been shutting off randomly. It first happened when I was driving uphill to my street in 3rd. I began to slow down to make the turn onto my road. When I downshifted to 2nd, before I could get on the gas again, the engine died. All the lights came on just like when it stalls. It started up right away, and drove off fine. Then a few days later, it happened the exact same way in the exact same spot. WTF That made me really confused, and I thought that there mgiht be a forcefield near my street... But then it also happened in 2 other places. I was going uphill about to turn into my driveway, downshifted, then died. Then I was going uphill approaching a stop sign, downshifted, then died.
What can I check? I couldn't find anything related to the car dying when going uphill.

 

[PieEyedPiper]

I would imagine starting with the simple things is best.
Do you vent your SSQV?

 

[SwitchSkier]

I would imagine starting with the simple things is best.
Do you vent your SSQV?

Of course not! The car never did it before, it just started about a week ago. It does it about once a day now, and always either when I press the clutch in to downshift at my driveway, or street. They are both uphill on relatively steep hills. About a month ago the car used to have a problem of dying as soon as it started like it didn't have enough power, but I tested my battery and it was fine. Then it just magically stopped happening.

 

[98mitsuGSX-SD]

Like the previous person said. Are you venting your B.O.V.? The loss of already metered air will cause your engine to run rich and if your going from boost to no boost your car can stall out and shut off. I've had it happen a few times when I was venting my B.O.V.

**Edit**
Maybe a fuel delivery issue?

 

[turbobird14]

Like the previous person said. Are you venting your B.O.V.? The loss of already metered air will cause your engine to run rich and if your going from boost to no boost your car can stall out and shut off. I've had it happen a few times when I was venting my B.O.V.

**Edit**
Maybe a fuel delivery issue?

this is a very good point but it would do it going downhill as well. This wouldnt be just an uphill occurance. Are you riding the gear out when you are downshifting or are you matching RPM when you downshift( bliping the throttle and letting out the clutch when you match the rpm so it feels really smooth when you shift into a lower gear) maybe your too low of an rpm and its stalling out?

 

[turboAWDfanatic]

Lightened flywheel can make it easier to stall out.

Does the car jerk at all (i.e. when you stall it by letting the clutch pedal out too fast?)

Some good mantenance issues to check right off the bat to rule them out:
1) Boost leak check
2) Set base timing
3) Set idle speed
4) Check spark plugs

You can find how to do these in a factory service manual, haynes/chiltons, VFaq, or in forum archives

 

[Clutch GSX]

my vote is spark plugs. easy and cheap to check.

 

[SwitchSkier]

this is a very good point but it would do it going downhill as well. This wouldnt be just an uphill occurance. Are you riding the gear out when you are downshifting or are you matching RPM when you downshift( bliping the throttle and letting out the clutch when you match the rpm so it feels really smooth when you shift into a lower gear) maybe your too low of an rpm and its stalling out?

It stalls before I can get into the lower gear, when I'm in neutral. The lighter flywheel could be it. I realized that it looks like when I push in the clutch, the RPMs drop so fast that it goes too low and stalls. I haven't changed the spark plugs since I got the car but they are sitting in my garage. I am just waiting untill my next oil change so I can Seafoam, then put the new plugs in.
I recently did a boost leak test, and everything was fine. My idle holds steady at 750. And the timing looks good on dsmlink.