3.4 with stock fuel rail, and 19# injectors, stock 86V6 chip, timing is at 11º

The IAT sensor broke, so we just disconnected it, wonder if this would cause our problem. Car is running 93 octane gas, and runs alright when just driving. If you try to go to 4th (4spd) when going to slow, the engine starts to ping pretty bad. Same thing when you just start to go from a stop, as you let out the clutch, there is a half second or so when it pings until the RPMs begin to climb.

Would the 1 degree extra of timing really matter?? (I'm running 12 on my 2.8). Or is it the lack of IAT sensor that is causing the ping maybe? Anything else it could be?

Lastly, the coolent temp sensor for the ecm (under the thermostat housing) cracked a bit so I can't tell which way the plug shold be inserted. Does it matter if the plug is flipped? When I unplug it at idle, the RPMs jump up, then as I reinsert the plug, they drop back down. Doesn't seem to change whichever way I plug it in, but I put it so it fits best, heh. Is there a 'right' way? (I plan on getting a replacement eventually, but for now....)

thanks,
John.

Well I call the IAT the MAT sensor and yes you need it. It tells the ECM what the incoming air temp is. If it is disconnected it will set a code and give the ECM a default value. The ECM temp sensor must be plugged in correctly or it also will set a code and give the ECM a default value. Car should not ping at 11* and 93 octane.
I would replace the sensors, see if that solves the problem. If the connectors to the sensors are worn, you can buy new ones at most auto parts stores.............Paul

If you lived a little further south where it is warm all of the time, you wouldn't have to replace your IAT.

Thing is, it was a 4cyl car, so we didnt' avhe the V6 air box. Dropped the lil dukie for a 3.4. Going to dig up the IAT/MAT? sensor and see if that helps...

Still curious about that CTS...

Any temp sensor is just a variable resistor and they are not polarized....meaning it does not matter the way it is connected. (A small current is feed to the sensor and depending on temperature, the sensor will vary resistance.) Make sure the connections are good so it does not read wrong.

The temp sensors are used for several things but mainly timing and A/F mix. You really want both the ECT and IAT/MAT working or the engine likely won't ever run right.

Yes, you may have problems beyond that but you have to fix the sensors or you'll never get the rest.

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Edison Carter: When did the News become Entertainment?
Murray: Since it was invented.

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Specifically, the Fiero uses what's known as Speed-Density to determine how much air is entering the motor and therefor how much fuel to add in order to arrive at the correct mixture. Instead of measuring the air directly with a mass airflow sensor like many other cars, the Fiero ECM measures the vacuum and the temperature of the incoming air. The temperature is important because it affects the density of air, and since fuel is added based on the mass of incoming air instead of the volume of incoming air, it is important to know the temperature. The MAP sensor measures the vacuum, which when combined with the engine RPM can be used to calculate air flow. So, if you disconnect your air temp sensor the ECM defaults to some generic tables which keep the engine running, but at reduced power and efficiency.

In other words, you should fix it properly.

JazzMan