90 stalling issue solved

[rufcar]

In the end my friend has a 91 and we swapped his parts to mine and vice versa. Nothing helped, then he remembered from his days in GM class about how gm could not solve the problem but came up with this adjustable vacuum valve inserted into the T fitting above the fuel pressure regulator. It no longer stalls. Though I can force a stall buy going say 50 and come to a fast stop to zero without downshifting. I can live with that. He didn't remember what the part was called or where to get one, but he had one.

[grahambehan]

Interesting, introducing a variable vacuum leak "fixed" the stalling issue.
Graham

[rufcar]

Graham, we tried all the standard procedures. My computer on his car would not stall his car. His computer in my car still stalled. Changed all the sensors, did all the step counts, checked pump pressure, Injectors are 5 yrs old with 5k mi. The vacuum adjuster seems to do the trick.

[grahambehan]

Basically opening the throttle blades, ie allowing more air at idle. Is your car modified or stock ? Do you have any data logs of the stall condition? If so, what are the IAC counts at a warm idle? What is TPS voltage with closed throttle?
Graham

[Starman]

That?s just a needle valve


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[XfireZ51]

Varying the vacuum at the FPR varies the fuel pressure. I used this approach on my 84 Xfire so as to be able to use TBI injectors large enough to feed a modified motor at WOT and yet idle properly. But to do that required code so the injectors metered fuel correctly at all vacuum levels. We don?t have anything like that in the LT5 code.