Motronic 1.0 problem

[bpoliakoff]

I have an 81 Euro car with Motronic 1.0 from what I have learned over the years this was a 6 month only production and no one I have been able to find really knows the system. My problem is the 115 degree temp sender in the thermostat housing. When connected sends voltage to the ECU and makes the car run rich and idle over 2000. When disconnected the car idles perfect at 850. The car is still on the tail end of a 12 year nut and bolt resto so I haven't driven it yet. Any thoughts??

[plip1953]

I have an 81 Euro car with Motronic 1.0 from what I have learned over the years this was a 6 month only production and no one I have been able to find really knows the system. My problem is the 115 degree temp sender in the thermostat housing. When connected sends voltage to the ECU and makes the car run rich and idle over 2000. When disconnected the car idles perfect at 850. The car is still on the tail end of a 12 year nut and bolt resto so I haven't driven it yet. Any thoughts??

I've been pondering about how this sensor works, or more specifically how to test that it is actually working. My conclusion thus far (and there other threads on the topic) is that the primary purpose of sensor unit is to act as an on/off trigger for the idle enrichment injector. And that this is necessary as an aid to cold starting. BUT, that is should only allow this extra injector to run for a very limited time (coolant temperature dependent?) and then shut down the injector. Could it be that with yours the extra injector stays permanently on unless the connector to it is removed?

Have you tried running the car with the connector permanently off? Does cold starting become a problem? If you can't source a replacement maybe you could simply get into the habit of starting with it connected and then shortly after disconnecting it until your next cold start?

[bpoliakoff]

It does start with it disconnected. Fires right yp. What';s bothering me is having a loose connector and unused sensor I have all sensors new in the car and a tested good ecu

[plip1953]

It does start with it disconnected. Fires right yp. What';s bothering me is having a loose connector an d unused sensor I have all sensors new in the car and a tested good ecu

Do you have anything close to a "proper" cold start in Arizona? lol

I know what you mean. I get very irritated if anything isn't working just as I think it should. I assume the sensor in question one of the new ones? OE?

[bpoliakoff]

Can't tell brand. Part came from Walloth and Nesch so I would thing decent quality??
Only 120 miles north where it snows. Believe it or not 2 ski area with plenty of snow in the winter. Spoke to the friend who is tidying up all the bits that were missed during the process and the cold start valve is not the issue. Now to the next headache. Yesterday My friend was ready to call me and say pick up your car and drive it home. Finally after 12 years. 20 minutes later I get a call with a problem. He was doing the final torquing of the head and found one of the bolts to be stripped and not take any torque over 40#s. The frigging engine builder sent me a gift as he either stripped it or just shined it on.. A bore scope ascertained there were only 6 threads left in the hole. So the had to come off. Next concern. Could there be a crack in my M90 block? A sleepless night and my friend called me this morning and all is well. So we will helicoil the hole buy a $200 head gasket and hopefully be driving by weeks end. It just doesn't stop!!!

[jps635]

Geez Bert that is gutting - I can understand how you must feel. I hope the helicoil works ok. I would replace the bolts if any have been torqued to yield.

I have attached a couple of motronic docs that I found yonks ago, not sure of they will tell you anything you don't already know. If the don't open PM me your email

[bpoliakoff]

I have the full schematics for the car, but thank you. We are getting juice at the correct pin on the harness to the ecu from the sensor. Right now I will run without it. But will call 2 Motronic gurus I know tomorrow and see what they come up with. If the problem cant't be resolved I will switch to Motronic 1.3 which is an easy and affordable conversion. Last go round was a trans leak which we thought was the last issue to be resolved. I had resealed the trans before inslling it only to find a trickle of a leak. It turns out one of the bolts in the front housing goes all the way through the case and I should have put sealant on it. Well hopefully that is the last mechanical issue and I can finish trimming the car out and finally drive it.

Oh it wasn't the bolt that was stripped, it was the hole itself. The bolts are all good

[86_6series]

Hey Bert,

Sorry to hear about the head bolt. Are you going to replace with TTY bolts
or studs or non TTY?

I like the theory of TTY bolts but they are a pita when replacing a head.

Try not to stress out too much which is difficult I know, I've had many sleepless nights
on my build.

I wish you luck with an easy fix. Stay safe.

Bob V

[bpoliakoff]

Just going to stay with stock bolts. Engine isn't built that hairy Again, t wasn't the threads on the bolt that gave put, it was the threads in the hole and when we pulled the bolt it looked like the engine builder had got it cross threaded to begin with. Makes me feel like I should have assembled it myself

[bpoliakoff]

Looks like the I have the answer. One of the E9 people who is an absolute Motronic guru gave me the ohm numbers we should be getting at the ECU. Mine are so low it is causing the ECU to read a temperature of -0. Obviously I have a short in the wiring but at least I know where I have to look.