Car is shutting off when driving


New Member
Just started to get my Buick on the road after sitting for the colorado winter. Drove it around the block and noticed when I would slow down/ come to a stop the car will start to stall out or completely die on me. All my lights stayed on and one of the times I was cranking for about 30 seconds before anything happened. This never was an issue last summer when I was daily driving the car. It’s an 85 grand national with the engine from an 86/87. Still pretty new to the electronics in this car so curious if anyone else has had this issue and what it could be causing it. I haven’t seen any ground issues or battery wiring that’s bad. Did spark plugs and wires about 500 miles ago. I have fresh fuel in the tank and it has a hot wire kit so It doesn’t seem to be a fuel issue. I do have a scan master in the car and am still learning to use it properly to diagnose. Any help would be greatly appreciated!
Might need to look for vacuum leaks so boost/leak test it. You'll want to keep an eye on all Scanmaster readings and post up what you can.
It's the Crank Sensor.

At least an 80% chance.

Get back to me......
Not saying your not right but i guess i am one of the lucky one's..
5 TTA's, one Ttype and my current 87 GN and not one bad crank sensor in any of them..
Maybe i should buy a lotto ticket.. nay never win shit.
Might need to look for vacuum leaks so boost/leak test it. You'll want to keep an eye on all Scanmaster readings and post up what you can.
Have a good way to boost leak test the car? It’s my first turbo car so still new to it all
When your getting the no start problem are you sure the fuel pump is turning on.and where in Colorado are you at? I'm in Southern Colorado. PUEBLO
If the car fires up when it's cold and then shuts off when warm...and then refires if you wait about 20 guess would be the ignition module. Data from PL or SM would help.
EBay, boost leak tester
Tons of easy to use ones now but you must know your inlet pipe/tube size, maybe 2.5" or 3". Then you need compressed air and soapy water then spray away.

The smoke tester is better, I call it the Cheech and Chong machine but the shops charge a decent amount to use it. Making it might be useful if you're into that.
Throttle plate or IAC might be out of adjustment. Check your idle IAC numbers. 10 hot in park at idle is optimal.
Did you check fuel pressure and confirm the fuel pump is running when this happens? If you have no fuel pressure or don’t hear the pump run, try bypassing the Hotwire kit relay(plug the factory fuel pump wiring back together at the tank) next time it happens. I had this exact problem and it was a faulty relay in the Hotwire.
I finally had a chance to get some numbers off the scanmaster. Been working overtime everyday the last few weeks so havent had a chance to hop on here and upload. Appreciate everyones responses. drained the tank and put fresh e85 in, replaced the filter, and repaired some grounds, also charged the battery and seemes to idle just fine. going to drive it again around the block today to see if the issue is still there or i was just being an idiot. heres my numbers.

IAC - 01
TPS - .44
r - 950
Ats - 55
Clt - 95
bL - 142
Int - 128L8 - 26
AF - 04
NAL - 00
cc - 45