Weird engine temperature

We have an issue today where we've removed the aftermarket chip and now experiencing an overheating problem. However, note that when we turn on the AC/heater the engine begins to cool.

We've also preformed the poor-boys diagnostic and pulled, what we believe is code 33 (EGR opening not detected). For those who already know, during the "pre"diagnostic, the computer probes all the sensors and has shown the fan is working properly.

Something else more or less of subject, the car is running with the stock computer, an E303 cam, heads and so on with idle RPM around 850 with the IAC connected. I've never in my life seen a stock J4J1 computer handle an aftermarket cam and heads this well before.

It might have nothing to do with the problem at hand, but maybe worth mentioning.

Any ideas on the overheating issue? Thanks!

yeap, the highspeed fan is working. We've proved that when putting the EEC into diagnostic mode.

Don 95Vert said:

The 'by the book ' diagostic procedure for a bad ECT sensor is to see if the fan comes on when the AC is on. Yours must be because it is cooling. I'd wager to say the fan is not coming on when the AC is off. Get a Ford ECT sensor. It's on the heater hose junction on the front of the engine - two wires.

Don

Click to expand...

Okay, in this case, you're right on the money. When we turn on the A/C the fan is on and doesn't turn off. As soon as we turn the A/C off, the fan turns off and remains off.

For all intents and purposes, we unplugged the ECT, started the car and the fun runs no matter what.

Does this help?

It just seems interesting that this problem has only presented itself since we removed the JMS chip. The programming for the chip indicates fan comes on at 185*. Perhaps the ECT was feeding the chip false readings or the chip was collecting engine temperature from a different source?