Did I find the weakest link?

[JShadzi at aol.com]

Cody, over pressurizing an ISV shouldn't really be a problem as they have more or less equal pressure on both sides of the valve, the pressure differential across the valve is typically nill.  

Now, if you're just venting one side directly to atmosphere, and not back into your intake system, then it would be understandable why you're having so many failures, I doubt the valve is designed to hold a 1.5 BAR pressure differential.

Javad

>I've been waiting on my 5ktq to show me the weak points on these cars for a while now, and basically I have been just running too much boost. Until this Saturday I had been on the road for a year between 2 5ktq's (each for roughly 6 months continuously) running 2.5bar with not even the slightest sign of anything even dreaming about breaking,except about 2 months ago I had an ISV get stuck wide open which I though was just a plain failure by age. Saturday night though after a long 4th and 5th gear boost run I went to downshift and exit the highway and noticed my engine was idling at 2300rpm. After checking all of the vacuum lines and finding them to be perfect (was fairly confused at this point, all hoses ok, throttle fully closed) I remembered that last time my ISV went bad it did about the same thing. After squeezing one of the rubber connections with the engine running I found that the ISV was indeed the issue. For the ride home I plugged up the valve with a piece of a sho!
>p rag and turned up the idle with the TB screw. I'm going to go ahead and remove the valve for good now and plug the holes on the manifold.
>
>Anybody else heard of ISVs failing because of being overpressurised? Maybe I'll see what I can do about repairing it and find out exactly what went bad inside.
>
>-Cody Forbes
>http://www.500tq.com
>'86 5ktq
>'87 5ktq EFI/K27 and now manual idle adjustment
>'88 80 4cyl
>'88 90 4cyl
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