Stalling at quick stops

[rufcar]

My 90 zr1 started to stall when going from say, 40 to a stop. Turn the it fires right up. I spoke to Hibeck and he said just try and downshift to a stop. I have done that for the last 6 or more months and its been ok. A 2 weeks ago I came to a stop at a very crowed intersection, and someone cut me off and had no time to downshift and it stalled while moving like previously, so I caught it in gear like I have done before except this it stumbled and left me sit in heavy traffic. I pushed it to the side and it would start for 1 second and stop. I tried a few times and the same thing, so I called a tow service. About 45 minutes passed he showed up and the car started. I had him tow me to a friend's shop who has a zr1 and works on some. He had it a few days tested everything. No codes either. He changed out the fuel filter and tore it apart and it was ok so He installed a new one. The PO replaced everything as he was a GM wrench. Both pumps are new so is most every relay and hose including the starter. I had a spare NOS idle control valve so I removed the old one cleaned the area as there was some carbon installed a new one and I tried to make it stall and I couldn't. I thought I had it and the last stop coming home it did again. I could live with that as long as I never get the no start again. I also checked the throttle plate, and it was super clean. Any suggestions?

[1991 Corvette ZR-1]

The MAP sensor line or perhaps the sensor itself? It is happening when you get on the brakes, which are assisted by vacuum and to me it sounds like a hiccup in the engine management when vacuum changes suddenly. I had the same issue years back when the throttle blades were closed at low speed and attempting to make a turn. When off the gas and applying the brakes for the turn, the engine would stall.

In my case, it ended up being a poor choice by a previous owner for replacement MAP sensor line that was full of oil and softened to the point it collapsed under any vacuum. Once this was replaced with a proper hard line, there were no further issues.

[rufcar]

did not check it as I know its been replaced by a proper GM unit about 3k mi ago.

[-=Jeff=-]

Do you have a custom chip in the car?

[rufcar]

yes Hibeck

[-=Jeff=-]

ok. I had an issue with a chip before, but I am confident my issue wont be in Haibeck's chip