Since I got the fire damaged $50 '91 GT running I have had intermittent check engine lights. The code is 1214 which is an intermittent temp sensor 2 failure (LH computer). The failure rate has been increasing over time. Fails only during or after heavy throttle. Never fails during slow around town or steady cruise at any speed.
The engine harness and all sensors were replaced during rebuild. First I replaced the temp sensor 2 again. No effect. Then checked harness for problems and found the temp sensor 2 connector housing installed backwards on the new harness, so it would not lock. Turned it around and still failed. Then ohmed and examined the wire and crimps to no avail.

I was going to post this to see if anyone else had these symptoms but then remembered that I had installed a 75 C thermostat during rebuild. Installed an original 83 C thermostat and no more problems.

I guess the steady cooler temperatures during cruse followed by the increased temperature of heavy throttle was sensed as a temp 2 sensor failure.

It's probably my imagination, but the car seems to have more power. Or maybe, the LH was retarding the spark to try to solve the perceived temperature problem?

It makes me wonder, could this be why some earlier LH cars without the check engine light ('88,'89,'90) are down on power? If you are running a 75 C thermostat and have access to a Bosch Hammer, it might be interesting to check.

Others have questioned the wisdom of running a 75 C thermostat for other reasons. A 75C thermostat will not fix cooling problems, so why use them?

I do remember dynoing in Hallet OK with the '88 in 1990 with ambient at 106F. I can't remember which thermostat I was using but, the last and hottest run had the most HP and torque.

To see why my '91 GT cost only $50, go to my website: http://members.rennlist.com/captearlg/

Earl Gillstrom '91 GT

 

And with that, I think you have become the owner of the best deal on 928 wheels. I have had some incredible deals, but nothing like that Earl. The car is starting to look like a new car, good work ....

 

On my previous S4 5sp I tried the 75C thermostat just to see what it would do, but promptly switched the 83C back in. All the 75C version does is prolong the cars warm up until it has reached the point were the fan(s) begin to operate.........pure and simple. It actually may allow the car to run too cool on colder days producing poor power, poor mileage, and more internal wear.

Problem is there are many 928 owners who simply don't like how their temp gauges "read", and so the knee-jerk reaction is to stick in a lower temp thermostat. Or they really do have a cooling problem and want to try and fix it for $10 instead of fixing it right........

My GT is an absolute bear once it has warmed up to its correct operating temp which is what some will think is too hot on the gauge......but its right where it should be.

 

Heinrich,

I don't give a complete description on the website. I spent over $10,000 for new parts and supplies and 8 months continuous labor, but it looks and drives like new. That includes all wear or time deterioriate parts. All work was done by me at home including paint. (My paint supplier did some quick calculations on labor and figured I exceeded the value of the car, but since I work for myself free, I don't count that, and it does keep me off the street). I do consider the car finished. I was lucky that the interior is like brand new and has supple leather seats. unfortunatly there are no extra leather options. Like you, I like full leather interiors.

 

That describes my '89.

Quote:

If you are running a 75 C thermostat ...

Earl, is there anyway to tell? Is there a big 75C stamped onto the thermostat? Or do you have to throw it in a pot of water like a round metal lobster?

 

David,

There is a small 75 or 83 stamped into the thermostat. As I recall it is on the flat part that acts as the valve that goes against the rubber seat that is in the motor. It is very obvious.

 

Thanks Earl.

 

Hopefully, I found the problem with my false check engine lights. I powder coated the thermostat housing when I did the other parts and it was partially insulated from the engine. With an ohmeter, there was varying resistance. I scraped the powder coating off under the bolts and all is well. Most sensors have thier own ground wire but the temp sensor 2 requires an engine ground.

 

Hi Earl,
The type of thermosstat won't affect fuelling controlled by the LH. The fuelling is related to water temperature, given by the temp 2.

The only time you get a problem is when you had this intermittent sensor signal to the LH. If changes of water temp reported to the LH are more rapid than it would expect, then it assumes there is a fault, and just goes to some default fuelling settings. This was why you though the power was down somewhat.

Anyway, glad you fixed it OK !