Nearly certain there is an AFM/Engine Temp Sensor problem...

CJFusco · CJFusco's Garage

Today it is 67 degrees (and rainy), and the 944 is pulling stronger than it has in months. Yesterday it was 95 degrees and it felt weak... until the sun went down, when the temperature dropped to 72 or so. Then the car ran great.

Is this enough to justify an assumption that there is something wrong with my AFM box or Engine Temp Sensor (or DME)?

Thoughts?

944S Boyeee · 08-01-2003, 12:41 PM

Mine is like that. These cars don't like hot air coming in.

On crisp, cool nights, my car feels totally different.

944S Boyeee

carsontc · 06:19 PM

Mass...Nova Scotia...cold air....that does it...I'm running a 3" PVC duct from my AC output in the dash direct to the airbox...lots of duct tape...boost? crank the fan to high!

question...will my early 85 ring & pinion handle this or should I go with a turbo transaxle? (I will prolly want to abuse this set up and be tempted into doing some wheelies)

TCMdocs944 · 08-02-2003, 06:11 AM

CJ I thought about this while I was sleeping (don't ask) and, though not sure, it seems the engine temp sensor is out. It only measures block coolant temp for the dme.

As I understand it from wilks' site the AFM only measure air VOlume, nothing to do with temp.

Humidity is out, as it was better rainy.

I don't know if anything actually measures intake air temp for the dme. I do know from the factory manuals that all test/repairs should be performed with an ambient air temp of 68 degrees f.! This may be the prime operating temp (average german air temp) for the P car?

CJFusco · CJFusco's Garage

TCM - thanks for the imput... I know that all cars typically drive better in cool air, maybe doubly so for such an old car. I guess I am just worrying myself needlessly.

Oh well, nice long drives to look at the foliage in October will see the car running at 100%, at least!

dfrac · 08-02-2003, 06:51 AM

Actually the AFM has a temp sensor inside of it. How else can it compensate for different air temperatures?

Porsche944 · 08-02-2003, 10:43 AM

You can test the temp sensor in the AFM with an ice cube and a meter. F.R. Wilk has pinouts, schematics, and part locations on his DME web site.

To test the sensor, connect a digital meter to the sensor leads and hold the ice cube against the sensor. Because the sensor has a negative temperature coefficient (higher resistance at colder temperatures), you should see the meter reading increase as the sensor cools. Remove the ice and the meter reading should decrease.

If the sensor is not operating properly the DME cannot compensate for air density changes due to changes in ambient temperature. This will cause the fuel/air mixture to be off.

ronin · 08-02-2003, 10:48 AM

Quote:

Originally posted by carsontc
Mass...Nova Scotia...cold air....that does it...I'm running a 3" PVC duct from my AC output in the dash direct to the airbox...lots of duct tape...boost? crank the fan to high!

question...will my early 85 ring & pinion handle this or should I go with a turbo transaxle? (I will prolly want to abuse this set up and be tempted into doing some wheelies)

lol, humor should never go unrewarded. Sounds like something you'd see on the Red Greene show. This could make a really cool April fools tech article for Excellence magazine or something.