I am having a problem that I thought another owner may have encountered.
My 90GT starts right up and run great.......for a few minutes. Then, after about 2 minutes it starts to run VERY poorly and can barely be kept running. It's seems to be getting either way to much or way to little fuel? It's so bad that at full throttle it will hardly reach 3000 in first gear. When, after about 5 minutes it clears up and run 100% perfectly. If I park the car for a while then start it up again it goes through the same scenario again?

Any ideas on what's causing this would be greatly appreciated.

One possibility is a faulty Temp II sensor.

Temp II Sensor
This is a dual-element temp sensor mounted on the top front of your engine.


Inside the sensor are two independent sensors, with one telling the EZK {ignition} ECU the engine temp, and the other telling the LH {injection} ECU the engine temp. (Earlier cars have only one sensing element.) Find the sensor. It is screwed into the top of the engine, just to the right of center, at the front. Remove the wire lock before trying to unplug the harness.
On the top of the sensor, inside a rectangular recess, will be two small pins. Measure the resistance from each of these pins to the engine. Do not measure the resistance between the two pins. The resistance should vary
with the engine temperature (not air temp).

32 deg F resistance should be 4400 - 6800 ohms.
59 deg F to 86 deg F, resistance should be 1400 - 3600 ohms.
104 deg F, resistance should be 900 - 1300 ohms.
140 deg F, resistance should be 480 - 720 ohms.
176 deg F, resistance should be 250 - 390 ohms.

If the resistances at the sensor are correct, reattach the wire harness and then repeat the measurements between terminals 13 and 17 (NTC connection and Gnd)  at the disconnected LH multiple pin plug. In other words, pull the large connector off of the injection ECU and check the resistance there to see if there is a problem in the wire harness.
If the injection ECU (the LH unit) is not connected to the Temp II sensor, the mixture will be full rich, and the engine will not start or run when warm.

ps: to verify the Temp2 sensor to EZK connection do a measurement in the disconnected EZK connector between pin 19 (NTC) and 18 (Gnd).

Wally Plumley (and Theo)
928 Specialists


Perhaps this will help.

Temperature - Resistance values for the Temp II Sensor:
0 deg C - 4.4 - 6.8 kOhms
15 to 30 deg C - 1.4 - 3.6 kOhms
40 deg C - 0.9 - 1.3 kOhms
60 deg C - 480 - 720 Ohms
80 deg C - 250 - 390 Ohms

Wally Plumley
928 Specialists

The temp2 sensor connection can break due to heat and age:


This is how to repair: