I think I have figured out why the engine was going crazy when it hits 165 degrees. I installed a hot air box from a Cadillac North Star set up, to aid in warm up of the engine. That temperature of 165 must be the temperature at which the box crosses over from heated air to cold air. I was able to out smart it by increasing the warm up enrichment at 165 degress. But the question is this: Why does the IAT sensor, the one which sends to the ECM the temperature of the air coming into the throttle body not automatically correct for variations in intake air temperature? You would think the program would accomodate this kind of change, and make adjustments automatically. Al T stated that his engine ran better after he started drawing air from outside the engine compartment. But again, I have the same question, why would the computer not adjust for this? You would think as the temperature goes up, there would be a compensating multiplication in the string that determines the pulse width. Any thoughts on this?

Does anybody know of another vacuum valve which will switch the vacuum off at a higher tiemp than 165? I picked this part at random from a 1985 Ford F 150, simply because I know that model has such a part. I would like one that cut off at 190 or so.
Sam

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Does your computer have any outputs that toggle with temperature? If it does, you can use an ordinary solenoid and set the computer at whatever temperature. Maybe an idle solenoid output?

In theory the computer should compensate for intake temp differences. As long as the temp sensor reacts fast enough (an open cage type, not a potted type like coolant sensors) and the multiplying factors it uses are tuned just right.

The ECM has cooling fan onand off settings, which iare currently being taken care of by the thermostat that came with the fans. Does anyone know of a vacuum switch controlled by an elctrical solenoid. I have a couple of old vent canister purge solenoids, and that would work, but they are rather large. If anyone knows of a smaller one tht would be appealing.

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Napa 2-2307 - 3/16" hose barbs, +12v solenoid. Original application is some chevy egr doohickey.

I got this from the megamanual fast idle section - it also mentions some part #'s for a "fuel tank selector" with bigger barbs thats meant to control gas coming from one tank or another but works as well for vacuum.

What service! Thanks man. When I did my MEga Squirt, I looked and did not find that part number in the manual, so I did not even look this time.
Maybe it is a recent addition, or maybe I had "manual blindness", a desease slightly related to "refrigerator blindness". Thanks again.
Sam

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I like the soleniods that come on the early 90s Eagle/Talons & Mits cars, they are mounted on the firewall on the drivers side. They are small and work good, I have never seen one go bad so going to the yards and getting one off a car would be OK. They are used for EGR,Purge & Boost control. This would also give you a wiring pigtail that you could cut off the car when you get the switch and there is a metal bracket that you can get for mounting. youc an even get the whole pack so you have others for projects down the road.


But one thing I am wandering is why you even have this inlet air change. You shouldnt need it for helping warmup with the EFI because of the other ajustments. But there is no maps or ajustments for the Air temp in the DFI system that I can see, everything is based off the ECT. So I think no matter what temp you do this switching from inside to outside air it is going to give trouble because it just doesnt react fast enough. If it did it would not be having trouble at the temp it is switching at. I would just set the box to outside air and leave it at that. I dont think you would ever have problems with Icing in the winter because of the turbo and the heat it makes. And Icing is not going to cause EFI much problem anyway, atleast not like it would a carb.


Jess

Heated air is designed to make the engine warm up faster. It does do that, and I would like to keep it if I can make it work. I am just glad to know why it got so squirelly. If I can;t make it work, I will just route the air from the outside as you suggested.

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