Running Rich
01-13-2004, 09:21 PM
#1
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Running Rich
Hey,
New to rennlist, but love it incredible the amount of info on here. I do have one question for yas. I have a 1987 Porsche 944 N/A, I drive it summer only being I live in Michigan and I would never think of driving it in them... For many reasons. But, however I do start it to move it on occasion. Which is my question when its cold and I go to start it, it fires right up but it smokes and is getting way too much gas.. Summer time it runs a perfect mixture. What are some possibilities? Thanks, I really appreciate any help.. Peace A.J.
New to rennlist, but love it incredible the amount of info on here. I do have one question for yas. I have a 1987 Porsche 944 N/A, I drive it summer only being I live in Michigan and I would never think of driving it in them... For many reasons. But, however I do start it to move it on occasion. Which is my question when its cold and I go to start it, it fires right up but it smokes and is getting way too much gas.. Summer time it runs a perfect mixture. What are some possibilities? Thanks, I really appreciate any help.. Peace A.J.
01-14-2004, 02:37 PM
#3
Three Wheelin'
the temperature sensors are NTC, or negative Temperature coefficient devices, which means the resistance of the device is inversely proportional to its temperature. When the device is "cold" its resistance is high and vice versa.
The good part is that you can check these devices with an ohm meter.
The first sensor is part of the air flow meter. To check it get an ice cube, a hair dryer and a meter. Remove the air box and disconnect the AFM from the harness. Connect your meter to the outside pins on the AFM plug (Check this at F.R. Wilk's site, I could be wrong.).
Take an initial resistance reading. Apply the ice cube to the sensor (small cream/biege colored cone in the upper right corner of the inlet) and watch the meter. As the sensor cools off the reading should increase. Now do the same thing with the hair dryer, except the resistance should decrease.
The second sensor is at the front of the engine near the intake runner for #1 cylinder. Look for a sensor with a blue connector. To test this sensor, disconnect the harness and take an initial reading with a cold engine, reconnect the harness, start the engine, let it come up to temperature, stop the engine, disconnect the sensor, and then take a "hot" reading.
Alternately, you can remove the sensor, but because the sensor penetrates into the engine coolant, you may make a little bit of a mess. If you remove the sensor you can use the ice cube/hair dryer method, or you can put the sensor in a pot of cold water, connect the meter, and then heat the water on a stove.
If the sensors check out, then you may want to take a look at the DME harness to make sure you don't have an open circuit.
If the sensors and harness check out, then you may want to look at the Idle Stabilizer. During the start sequence the DME looks at engine coolat temperature to determine if "cold start enrichment" is required. If enrichment is required the DME tells the injectors to fire longer and tells the ISV to maintain a specific idle RPM. For example, my '87 idles at about 1100-1200 RPM when cold, and then drops to 840 when the engine gets "hot". If the ISV has failed, or is sticking the the engine would run rich during a cold start and would return to a more normal mixture once the engine is "hot".
The good part is that you can check these devices with an ohm meter.
The first sensor is part of the air flow meter. To check it get an ice cube, a hair dryer and a meter. Remove the air box and disconnect the AFM from the harness. Connect your meter to the outside pins on the AFM plug (Check this at F.R. Wilk's site, I could be wrong.).
Take an initial resistance reading. Apply the ice cube to the sensor (small cream/biege colored cone in the upper right corner of the inlet) and watch the meter. As the sensor cools off the reading should increase. Now do the same thing with the hair dryer, except the resistance should decrease.
The second sensor is at the front of the engine near the intake runner for #1 cylinder. Look for a sensor with a blue connector. To test this sensor, disconnect the harness and take an initial reading with a cold engine, reconnect the harness, start the engine, let it come up to temperature, stop the engine, disconnect the sensor, and then take a "hot" reading.
Alternately, you can remove the sensor, but because the sensor penetrates into the engine coolant, you may make a little bit of a mess. If you remove the sensor you can use the ice cube/hair dryer method, or you can put the sensor in a pot of cold water, connect the meter, and then heat the water on a stove.
If the sensors check out, then you may want to take a look at the DME harness to make sure you don't have an open circuit.
If the sensors and harness check out, then you may want to look at the Idle Stabilizer. During the start sequence the DME looks at engine coolat temperature to determine if "cold start enrichment" is required. If enrichment is required the DME tells the injectors to fire longer and tells the ISV to maintain a specific idle RPM. For example, my '87 idles at about 1100-1200 RPM when cold, and then drops to 840 when the engine gets "hot". If the ISV has failed, or is sticking the the engine would run rich during a cold start and would return to a more normal mixture once the engine is "hot".
01-14-2004, 06:35 PM
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Thanks for the help guys, great to have the help. I'll hafta mess with it , now that I know what to mess with 
.. Have a good one, and thanks again, A.J.
.. Have a good one, and thanks again, A.J.
