924Board.org

bcblase · Joined: 23 Oct 2007 Posts: 574 Location: Winchester, VA

I am having some problems with my 924S that seems to be related to engine temp. When the engine is cold, it runs fine. When the car is totally warmed up or hot, the car runs fine.

But, when the engine is in the middle of cold and warm, it loses power and acts like it is not getting fuel. This has happened a few time when I have driven the car and not let the engine totally warm up before driving. It loses power at some point during the transition from cold to hot, but then it goes away when the engine fully warms.

It happened last night while driving on a cold night - I noticed the temp gauge heading south while driving around 70mph. As the engine cooled, the car started hesitating and evenually lost all power. I had to pull over and let the engine "warm up" several times to get the power back. I stuffed an old towel in front of the radiator to keep the engine from cooling down as much, and this helped a little, but I still had to pull over every 45-60 minutes to let engine re-warm.

Any ideas on what is causing this? a bad thermostat? air mass controller?

Thanks for any help,
BC
_________________
1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

This is neither here nor there, but I noticed your fans coming on after driving in cool weather. That is something mine do not do.
Normal operating temperature on my cars gauge is just under halfway. In hot weather at a stoplight it may rise higher till the fans come on and then it falls back. I noticed your temp needle above halfway which I thought odd for cold weather, but dismissed as differences in gauges.

dgz924s · Joined: 03 Nov 2002 Posts: 592 Location: Kansas

First thing to check is the DME temp sender.....
Turn the ignition switch OFF.
Disconnect the DME computer electrical connector.
Connect an ohmmeter between terminal 13 on the disconnected DME plug and ground.
Check for the following resistances:

DME Temperature Sensor Resistances
15-30 °C (59-86 °F) At 59 °F approximately 3.3 k-ohms
At 86 °F approximately 1.46 k-ohms

The sender is located near the AFM in the block w/blue housing and plug connector. Has a hex head for removal.

Try that and go from there.

_________________
Dal Glassinger

bcblase · Joined: 23 Oct 2007 Posts: 574 Location: Winchester, VA

The temperature switch for the cooling fan comes in several ranges - I figured that I had the lower temp switch (78 deg C or 83 deg C?) - I have seen them in a higher range also - 93 deg C also on various Porsche parts web pages.

The temp gauge normally runs right in the middle of the gauge.

I'll check the DME inputs as suggested.

BC
_________________
1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver

dgz924s · Joined: 03 Nov 2002 Posts: 592 Location: Kansas

FYI....The gauge is run off another sensor. The one you need to check is the one that "talks" to the DME/computer in which reads the temp and allows the DME to adjust A/F mix.
_________________
Dal Glassinger

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

Will your car warm up at all?

bcblase · Joined: 23 Oct 2007 Posts: 574 Location: Winchester, VA

bcblase · Joined: 23 Oct 2007 Posts: 574 Location: Winchester, VA

Took the throttle body apart tonight to get at the throttle position sensor and found this:

Vacuum line that runs from my throttle body - maybe this is the culprit. I'll be testing the TPS tomorrow.

BC
_________________
1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver

bcblase · Joined: 23 Oct 2007 Posts: 574 Location: Winchester, VA

Tested throttle position sensor (TPS) this evening. The three pin connector is for detecting closed, partially open, and full open positions of the throttle valve. The middle pin on the connector is ground.

When throttle is closed, resistance between the top pin and ground should be zero, slightly open <click> - inifinite resistance.

When throttle is closed, resistance between bottom pin and ground should be infinite, full open, it should go to zero.

Anyway, the TPS checked out Ok at room temp - not sure how it would do at higher temps where I am having my problem.

I'm going to replace the TPS anyway, and, of course, the melted vacuum line as well.
_________________
1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver