Ok my car seems to ben at least acting overheated by 245deg f. This is read by a scan tools because the gauge on the dash only shows 220. Anyway with a full tank of gas and a warmed up car the fuel pump will make a whining noise, the engine will stumble and stall, and the starter will refuse to turn at all. If I let the car sit for around 20mins and try to restart it, it is fine until the engine heats back up again. The strange thing is the temp stays around 245deg as soon as the second fan comes on and the GM dealership is telling me the engine should not be overheated at this temp. Anyway the intake manifold has now sprung a coolant leak at the gasket around the No. 8 cylinder. The fuel pump makes noises like an owl in the trunk only when the car is this hot and the gas tank will have extreme pressure too the point fuel will spray out. Again only when it is this hot. The car does have a Holley AFPR but the overheating issues have persisted before this. The car has also developed a rough idle since the first time it overheated probably due to coolant getting in cyl No. 8. Anyway if you have expierenced this and have a cure it would really be thankful. Also I haven't been able to find a PROM image that will work with my 1989 Iroc-Z 305 AT (well I found one that will run but the engine knock at WOT.) Maybe a factory image with different fan temps would help.

 

If the fans arent cooling the temp at all your thermostat is probably stuck closed.

The fuel pump is probably making noise because the fuel is getting hot enuf to vaporize. That would also explain the high pressure in the tank.

The car not starting when how could be either starter heat soak or vapor lock.

 

Hows the coolant level? If its too low, then you may have an air bubble stuck in the water pump or something, which would prevent the pump from pushing any coolant through the engine at all.. it would all just stand still.

 

The coolant level is fine 50/50 mix. The fans both works though with the factory chip they come on late. I pulled the intake (not as easy as it looks) and replaced the thermostat while I was in there. The radiator is new as are the upper and bottom radiator hoses. This may point something but I don't know, the car has a wierd idle it idles from 500rpm to 1200rpm and back down again. However the engine still pulls 17in/hg of vacuum on the vacuum gauge. Unplugging the MAF sensor as the book suggests results in the engine stalling and my scanner is showing a reading for the MAF sensor. The MAF sensor reads 6grams at 500rpm and steadly increases with the throttle. The valves have never been messed with and the timing is 6deg at idle with the diagnostic grounded. The car developed this funky idle after the first overheat leading me too believe that their may be unseen engine damage. Also the car exhibits a miss at these times. The IAC is clean and adjusted. I tried another computer and chip but the problem was still there. The car tries to stall if you put your foot in it too fast and is slow to respond to throttle changes. The engine has 90,000miles and the only modification is an adjustable fuel pressure regulator that is set at 42psi with the vacuum line off. I have determined that the smog pump bearings are worn but it still turns with only a little resistance. Any body else with this problem?