From: Theo Jenniskens [jenniskens@wxs.nl] Sent: Thursday, June 27, 2002 5:00 PM To: 928 Subject: [928] Temp Sensors Hi, I'm a bit confused about the temp sensors of a 1988 928s4. Standing in front of the engine, you see 3 sensors: 1. a copper colored sensor on top of the intake: the intake air-temp sensor that controls the fan for additional cooling even when the engine is shut off 2. just left from the water hose a blue looking sensor with a connector on top of it: the NTC II sensor, basically two NTC sensors, both providing a 300 ohms to ground when hot. One lead entering the EZK, the other one is entering the LH to provide engine temperature information. 3. right of the water hose a copper colored sensor with two spades on top, a bigger and a smaller one: the water temp sensor for the dash gauge. It should read 60 ohms to ground when hot (temp.level information), the other one is open (signals the overtemp condition, and is basically a switch) Is this correct? Theo '88 928s4 cherry red The Netherlands http://home.wxs.nl/~Jennit/Porsche.htm (on-line again on July 1st) -----Original Message----- From: Wally Plumley [mailto:wplumley@bellsouth.net] Sent: Sunday, December 22, 2002 1:08 PM To: 928 Subject: [928] Re: Your diagnosis - Runs poorly after good start At 02:29 PM 12/19/02, you wrote: >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. Dan, 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 ignition ECU the engine temp, and the other telling the 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 2 and 5 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. Wally Plumley 928 Specialists