air temperature sensor

[domlato]

How does this affect my 944 not starting. The car ran all summer last year and then in the fall stopped starting and has been garaged all winter. This has been an ongoing problem when car is running it may stop running and wont start but after sitting a while sometime minutes sometime days it will start and run fine until it decides it is tired and wont start. Temperature sensor was mentioned as possible problem by a mechanic.
Computer was rebuilt DME was replaced.
New battery installed after mention of proper voltage as being critical. Is air temperature sensor next step needed?

[kdjones2000]

Could very well be your speed/reference sensors.

Find the "DME Test Plan" and go through the diagnostic steps. Save yourself some $$ instead of doing the "replace-a-part" merrygoround.

[RedCarGuy]

Your mechanic doesn't know these cars very well because the 944 does not use an air temperature sensor.

I recommend finding a different mechanic who is familiar with the 944 or reading the library of threads on the no start/stall threads on this site and others.

[peteb]

Hi,

There is a air temperature sensor that is part of airflow meter. It is not available as a separate part, unless you want to do surgery on the air flow meter. The "temperature sensor" could also refer the DME coolant temperature sensor

They both need to be tested. I agree to approach this type of a problem in a systematic fashion using the DME test plan.

Peter

[guru944]

domlato;

The tempermental no start issue is common on German made cars, BMW, Porsche Audi/VW, Mercedes Benz, etc. All Harness were made by same manufacturer. " Greatest Common Factor"

"Could very well be your speed/reference sensors." Frayed wires.

Also verify and clean your Ground points. Especially by the Harness Ground Point located on to within 1 ft of your speed/reference sensors.
Using a DMM "Digital Multi-meter", set to lowest "ohm" Resistance setting verify ground from Battery (-) terminal to Ground test points. Your DMM /VOM should read "0.001" or less.... if not most likely you have a "floating ground", 99.8% of the cars have this issue. Especially the older cars. Body parts flex and electrical charges build up when there is a difference of potential between 2 points (Voltage). All vehicles have 3 ground planes which should terminate at the Batt (-).
So definitely clean and perform this check.

Keep us posted. Later...

[guru944]

Update:

I even had this intermittent issue on my 06 Cayenne S. Fixed it! Yes, a Floating Ground. Battery is located under drivers seat. Nuts. My Chariot has 184K miles. Thank God.

Later...

[Pauld_94S2]

The next time it quits running or won't start, VERY carefully unplug both reference sensor plugs at the back of the engine, one at a time, and plug it back together.

Yes, unplug and plug may fix your problems.

Unfortunately, the connectors used for the reference sensors get brittle and will crack or fall apart. When they crack, moisture can get into the interior and cause minor corrosion on the contact surfaces. Unplugging and plugging the connector wipes the surface corrosion off and usually the engine will start. Same problem for similar type connectors in the rest of the car.

[domlato]

Thanks to all who have offered suggestions regarding starting/running problems with my 944. I have not had time to follow any suggestions but about a month or so ago I tried to restart as I have done regularly all winter and it started. I let it run for a while, shut it down repeated a couple days later and started again as it has done many times before after sitting. I then started it up and backed it out of garage to clean the garage. When finished, tried to start and would not start again. One of these days if I can find a qualified mechanic, I will refer him to all of your comments and see what he can do. This car only has 82,000 mile and needs to be driven. Again, thanks